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I have been trying to connect to watermelonDB however i keep getting this error
TypeError : null isnot an object (evaluating 'DatabaseBridge[methodName]')
I looked all over the network but couldn't find a solution the problem that i am not generting or writing the DataBaseBridge it should be generated automatically with the packages ...
Can any one help with that urgently !!!
When working with music files, you might have wondered how to load display art from Audio files. In this tutorial, we will learn how to load thumbnails for audio files.
At the end of the tutorial, you would have learned:
To follow along with the tutorial, perform the steps below:
Create a new Android project with the default Empty Activity.
Replace activity_main.xml with the content below. This removes the default Hello World! TextView, adds a Button and an ImageView.
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<Button
android:id="@+id/button_loadMusic"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/load_music"
android:layout_marginVertical="16dp"
app:layout_constraintBottom_toTopOf="@+id/imageView_displayArt"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<ImageView
android:id="@+id/imageView_displayArt"
android:layout_width="300dp"
android:layout_height="300dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/button_loadMusic"
tools:srcCompat="@tools:sample/backgrounds/scenic" />
</androidx.constraintlayout.widget.ConstraintLayout>Add the <string> resource below into strings.xml.
<string name="load_music">Load Music</string>Download the sample music song I Move On by Jan Morgenstern ( copyright Blender Foundation | durian.blender.org). Upload the file onto your test device.
In AndroidManifest.xml, add the <uses-permission> element inside of <manifest>, but outside of <application>.
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>Currently, our project only has two elements: a Button and an ImageView.
At the end of the tutorial, our app should be able to perform the workflow below:
First, let us get the logic to load the music file out of the way. Follow the steps below to modify MainActivity#onCreate().
Obtains a reference to the Button.
val button = findViewById<Button>(R.id.button_loadMusic)Obtains a reference to the ImageView.
val imageView = findViewById<ImageView>(R.id.imageView_displayArt)The permission is required, so create a launcher to ask for permission below.
val permissionResultLauncher = registerForActivityResult(ActivityResultContracts.RequestPermission()){ isGranted ->
}Bind the permission launcher code to the Buttons OnClickListener.
button.setOnClickListener {
permissionResultLauncher.launch(READ_EXTERNAL_STORAGE)
}The API to get the thumbnail is different for devices running Android Q and above. So we will have to check for the version and call appropriate methods for each. Inside of permissionResultLauncher, add the code below.
val thumbnail = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
getAlbumArtAfterQ()
} else {
getAlbumArtBeforeQ()
}
imageView.setImageBitmap(thumbnail)Now we are going to create getAlbumArtAfterQ() first. For devices running Android Q or above, there is a dedicated convenient function to load thumbnails, ContentResolver#loadThumbnail(). The only things that are required to use this function is the Content Uri and a Size object. Because we already know the title of the song that we want to load the thumbnail for, it should be easy to query for its id. Adds the getAlbumArtAfterQ() function below into MainActivity.
@RequiresApi(Build.VERSION_CODES.Q)
private fun getAlbumArtAfterQ(): Bitmap? {
val collection = MediaStore.Audio.Media.getContentUri(MediaStore.VOLUME_EXTERNAL)
//The columns that you want. We need the ID to build the content uri
val projection = arrayOf(
MediaStore.Audio.Media._ID,
MediaStore.Audio.Media.TITLE,
)
//filter by title here
val selection = "${MediaStore.Audio.Media.TITLE} = ?"
//We already know the song title in advance
val selectionArgs = arrayOf(
"I Move On (Sintel's Song)"
)
val sortOrder = null //sorting order is not needed
var thumbnail: Bitmap? = null
applicationContext.contentResolver.query(
collection,
projection,
selection,
selectionArgs,
sortOrder
)?.use { cursor ->
val idColIndex = cursor.getColumnIndex(MediaStore.Audio.Media._ID)
while (cursor.moveToNext()) {
val id = cursor.getLong(idColIndex)
//Builds the content uri here
val uri = ContentUris.withAppendedId(
MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,
id
)
}
}
return thumbnail
}The code above simply queries the appropriate MediaStore collection to get the songs ID. With the ID received, we built a Content Uri with ContentUris#withAppendedId(). Because MediaStore knowledge is a requirement for this tutorial, I will not bore you with explaining the query further. You can read this tutorial to get an idea of how the query was built.
Now add the code below inside the while loop to load the thumbnail.
try {
thumbnail = contentResolver.loadThumbnail(
uri,
Size(300, 300),
null
)
} catch (e: IOException) {
TODO("Load alternative thumbnail here")
}loadThumbnail() can fail if the file does not contain a display art, so you can optionally catch the exception and load an alternative album art instead if desired.
To load the thumbnail for devices before Android Q, we will have to query the MediaStore.Audio.Albums(ALBUM_ART) collection instead. But because this collection does not contain the song title, which is our approach here, we will have to find the ALBUM_ART via one of the available columns in the MediaStore.Audio.Albums.
In this tutorial, we first find the album id in MediaStore.Audio.Media, and then use that album id to search for the ALBUM_ART in MediaStore.Audio.Albums. This approach performs two queries. You can also use a different approach, such as querying for the Album Title directly and you should be able to get the thumbnail in one query.
Add the getAlbumId() function to find the Album ID.
private fun getAlbumId(): Long? {
val collection = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI
//The columns that you want. We need the ID to build the content uri
val projection = arrayOf(
MediaStore.Audio.Media.TITLE,
MediaStore.Audio.Media.ALBUM_ID
)
//filter by title here
val selection = "${MediaStore.Audio.Media.TITLE} = ?"
//We already know the song title in advance
val selectionArgs = arrayOf(
"I Move On (Sintel's Song)"
)
val sortOrder = null //sorting order is not needed
var id: Long? = null
applicationContext.contentResolver.query(
collection,
projection,
selection,
selectionArgs,
sortOrder
)?.use { cursor ->
val albumIdColIndex = cursor.getColumnIndex(MediaStore.Audio.Media.ALBUM_ID)
while (cursor.moveToNext()) {
id = cursor.getLong(albumIdColIndex)
}
}
return id
}Now, add the getAlbumArtBeforeQ() function to query for the Album Art (it is a path String).
private fun getAlbumArtBeforeQ(): Bitmap? {
val collection = MediaStore.Audio.Albums.EXTERNAL_CONTENT_URI
//The columns that you want. We need the ID to build the content uri
val projection = arrayOf(
MediaStore.Audio.Albums._ID,
MediaStore.Audio.Albums.ALBUM_ART
)
//filter by title here
val selection = "${MediaStore.Audio.Albums._ID} = ?"
val albumId = getAlbumId()
//We already know the song title in advance
val selectionArgs = arrayOf(
"$albumId"
)
val sortOrder = null //sorting order is not needed
var thumbnail: Bitmap? = null
applicationContext.contentResolver.query(
collection,
projection,
selection,
selectionArgs,
sortOrder
)?.use { cursor ->
val albumArtColIndex = cursor.getColumnIndex(MediaStore.Audio.Albums.ALBUM_ART)
while (cursor.moveToNext()) {
val albumArtPath = cursor.getString(albumArtColIndex)
thumbnail = BitmapFactory.decodeFile(albumArtPath)
if (thumbnail === null){
TODO("Load alternative thumbnail here")
}
}
}
return thumbnail
}The function decodeFile() used above does not throw an exception. It returns null if it fails to load the thumbnail, so instead of catching an IOException here, we need to check for null and load alternative thumbnails if desired.
To test, we need to run the app on both Android Q (or higher) and an older Android API. In my case, I have used two emulators running Android API 32 and 22.
For Android 32, your app should behave similarly to the Gif below.
For Android 22, your app should behave similarly to the Gif below.
MainActivity.kt
package com.codelab.daniwebandroidnativeloadmediathumbnail
import android.Manifest.permission.READ_EXTERNAL_STORAGE
import android.content.ContentUris
import android.graphics.Bitmap
import android.graphics.BitmapFactory
import android.os.Build
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.provider.MediaStore
import android.util.Size
import android.widget.Button
import android.widget.ImageView
import androidx.activity.result.contract.ActivityResultContracts
import androidx.annotation.RequiresApi
import java.io.IOException
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val button = findViewById<Button>(R.id.button_loadMusic)
val imageView = findViewById<ImageView>(R.id.imageView_displayArt)
val permissionResultLauncher = registerForActivityResult(ActivityResultContracts.RequestPermission()) { isGranted ->
val thumbnail = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
getAlbumArtAfterQ()
} else {
getAlbumArtBeforeQ()
}
imageView.setImageBitmap(thumbnail)
}
button.setOnClickListener {
permissionResultLauncher.launch(READ_EXTERNAL_STORAGE)
}
}
private fun getAlbumArtBeforeQ(): Bitmap? {
val collection = MediaStore.Audio.Albums.EXTERNAL_CONTENT_URI
//The columns that you want. We need the ID to build the content uri
val projection = arrayOf(
MediaStore.Audio.Albums._ID,
MediaStore.Audio.Albums.ALBUM_ART
)
//filter by title here
val selection = "${MediaStore.Audio.Albums._ID} = ?"
val albumId = getAlbumId()
//We already know the song title in advance
val selectionArgs = arrayOf(
"$albumId"
)
val sortOrder = null //sorting order is not needed
var thumbnail: Bitmap? = null
applicationContext.contentResolver.query(
collection,
projection,
selection,
selectionArgs,
sortOrder
)?.use { cursor ->
val albumArtColIndex = cursor.getColumnIndex(MediaStore.Audio.Albums.ALBUM_ART)
while (cursor.moveToNext()) {
val albumArtPath = cursor.getString(albumArtColIndex)
thumbnail = BitmapFactory.decodeFile(albumArtPath)
if (thumbnail === null){
TODO("Load alternative thumbnail here")
}
}
}
return thumbnail
}
private fun getAlbumId(): Long? {
val collection = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI
//The columns that you want. We need the ID to build the content uri
val projection = arrayOf(
MediaStore.Audio.Media.TITLE,
MediaStore.Audio.Media.ALBUM_ID
)
//filter by title here
val selection = "${MediaStore.Audio.Media.TITLE} = ?"
//We already know the song title in advance
val selectionArgs = arrayOf(
"I Move On (Sintel's Song)"
)
val sortOrder = null //sorting order is not needed
var id: Long? = null
applicationContext.contentResolver.query(
collection,
projection,
selection,
selectionArgs,
sortOrder
)?.use { cursor ->
val albumIdColIndex = cursor.getColumnIndex(MediaStore.Audio.Media.ALBUM_ID)
while (cursor.moveToNext()) {
id = cursor.getLong(albumIdColIndex)
}
}
return id
}
@RequiresApi(Build.VERSION_CODES.Q)
private fun getAlbumArtAfterQ(): Bitmap? {
val collection = MediaStore.Audio.Media.getContentUri(MediaStore.VOLUME_EXTERNAL)
//The columns that you want. We need the ID to build the content uri
val projection = arrayOf(
MediaStore.Audio.Media._ID,
MediaStore.Audio.Media.TITLE,
)
//filter by title here
val selection = "${MediaStore.Audio.Media.TITLE} = ?"
//We already know the song title in advance
val selectionArgs = arrayOf(
"I Move On (Sintel's Song)"
)
val sortOrder = null //sorting order is not needed
var thumbnail: Bitmap? = null
applicationContext.contentResolver.query(
collection,
projection,
selection,
selectionArgs,
sortOrder
)?.use { cursor ->
val idColIndex = cursor.getColumnIndex(MediaStore.Audio.Media._ID)
while (cursor.moveToNext()) {
val id = cursor.getLong(idColIndex)
//Builds the content uri here
val uri = ContentUris.withAppendedId(
MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,
id
)
try {
thumbnail = contentResolver.loadThumbnail(
uri,
Size(300, 300),
null
)
} catch (e: IOException) {
TODO("Load alternative thumbnail here")
}
}
}
return thumbnail
}
}activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<Button
android:id="@+id/button_loadMusic"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/load_music"
android:layout_marginVertical="16dp"
app:layout_constraintBottom_toTopOf="@+id/imageView_displayArt"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<ImageView
android:id="@+id/imageView_displayArt"
android:layout_width="300dp"
android:layout_height="300dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/button_loadMusic"
tools:srcCompat="@tools:sample/backgrounds/scenic" />
</androidx.constraintlayout.widget.ConstraintLayout>strings.xml
<resources>
<string name="app_name">Daniweb Android Native Load Media Thumbnail</string>
<string name="load_music">Load Music</string>
</resources>AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.codelab.daniwebandroidnativeloadmediathumbnail">
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/Theme.DaniwebAndroidNativeLoadMediaThumbnail">
<activity
android:name=".MainActivity"
android:exported="true">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>We have learned how to load thumbnails on both pre-Q and post-Q Android devices in this tutorial. The full project code can be found at https://github.com/dmitrilc/DaniwebAndroidNativeLoadMediaThumbnail
Android provides many ways to perform background tasks, such as Services, WorkManager, or even threads. In this tutorial, we will learn how to create a Service for our Android app.
At the end of the tutorial, you would have learned:
To follow along with the tutorial, perform the steps below:
Create a new Android project with the default Empty Activity.
Replace activity_main.xml with the code below. This removes the default Hello World! Textview and adds two Buttons for starting and stopping the Service.
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<Button
android:id="@+id/button_startService"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/start_service"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toStartOf="@+id/button_stopService"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<Button
android:id="@+id/button_stopService"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/stop_service"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toEndOf="@+id/button_startService"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>Add the <string> resources below into strings.xml.
<string name="start_service">Start Service</string>
<string name="stop_service">Stop Service</string>In MainActivity#onCreate(), obtain a reference to button_startService.
val startServiceButton = findViewById<Button>(R.id.button_startService)Obtain a reference to button_stopService as well.
val stopServiceButton = findViewById<Button>(R.id.button_stopService)A service is a class that extends Android.app.Service. From the Service class, the only required function that we must override is the onBind() function. There are other functions such as onStartCommand() or onDestroy() for us to override as well.
There are three different types of Service:
null from the onBind() function.To create a Service class, follow the steps below.
Create a new class called SampleService.
class SampleService {
}Adds Service as the parent class.
class SampleService : Service() {
}Implements onBind() by simply returning null.
override fun onBind(p0: Intent?): IBinder? = nullThat is all that is needed for the Service to work, but let us add some basic functionality, such as displaying a Toast when it starts. To do that, we will override onStartCommand().
override fun onStartCommand(intent: Intent, flags: Int, startId: Int): Int {
Toast.makeText(
this,
"Service Started",
Toast.LENGTH_SHORT
).show()
return START_NOT_STICKY
}Also, override onDestroy() to display another Toast when the Service is stopped.
override fun onDestroy() {
super.onDestroy()
Toast.makeText(
this,
"Service Stopped",
Toast.LENGTH_SHORT
).show()
}Next, we will have to register the Service in the Manifest using <service>. In AndroidManifest.xml, inside of the <application> tag, add the <service> tag below.
<service android:name=".SampleService"
android:exported="false"/>android:exported=false is a flag that prevents other Apps from using our Service.
To start the service, we can call the startService() function from the Context object. It takes an Intent object. To enable starting and stopping the service, follow the steps below.
In MainActivity#onCreate, create an Intent to start our SampleService. Here, we pass in the context object and the Class object of the Service.
val serviceIntent = Intent(
this,
SampleService::class.java
)Now, bind button_startService to the startService() call.
startServiceButton.setOnClickListener{
startService(serviceIntent)
}Lastly, bind button_stopService to the stopService() function.
stopServiceButton.setOnClickListener {
stopService(serviceIntent)
}We are now ready to run the app. Pressing the Start Service Button should start SampleService, and pressing Stop Service Button should stop SampleService. Refer to the Gif below to check your Apps behavior.
SampleService.kt
package com.codelab.daniwebandroidcreateaservice
import android.app.Service
import android.content.Intent
import android.os.IBinder
import android.widget.Toast
class SampleService : Service() {
override fun onBind(p0: Intent?): IBinder? = null
override fun onStartCommand(intent: Intent, flags: Int, startId: Int): Int {
Toast.makeText(
this,
"Service Started",
Toast.LENGTH_SHORT
).show()
return START_NOT_STICKY
}
override fun onDestroy() {
super.onDestroy()
Toast.makeText(
this,
"Service Stopped",
Toast.LENGTH_SHORT
).show()
}
}strings.xml
<resources>
<string name="app_name">Daniweb Android Create a Service</string>
<string name="start_service">Start Service</string>
<string name="stop_service">Stop Service</string>
</resources>MainActivity.kt
package com.codelab.daniwebandroidcreateaservice
import android.content.Intent
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Button
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val startServiceButton = findViewById<Button>(R.id.button_startService)
val stopServiceButton = findViewById<Button>(R.id.button_stopService)
val serviceIntent = Intent(
this,
SampleService::class.java
)
startServiceButton.setOnClickListener{
startService(serviceIntent)
}
stopServiceButton.setOnClickListener {
stopService(serviceIntent)
}
}
}activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<Button
android:id="@+id/button_startService"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/start_service"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toStartOf="@+id/button_stopService"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<Button
android:id="@+id/button_stopService"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/stop_service"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toEndOf="@+id/button_startService"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.codelab.daniwebandroidcreateaservice">
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/Theme.DaniwebAndroidCreateAService">
<activity
android:name=".MainActivity"
android:exported="true">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<service android:name=".SampleService"
android:exported="false"/>
</application>
</manifest>We have learned how to create a Service in this tutorial. The full project code can be found at https://github.com/dmitrilc/DaniwebAndroidCreateService
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When working with Hilt, you might have wondered how to inject ViewModels into your application. In this tutorial, we will learn how to inject ViewModels into your app Fragments.
At the end of the tutorial, you would have learned:
To follow along with the tutorial, perform the steps below:
Create a new Android project with the default Empty Activity.
Create 3 new Fragments called BlankFragment1, BlankFragment2, and BlankFragment3 by right-clicking the main package > New > Fragment > Fragment (Blank).
Replace the code inside activity_main.xml with the code below. This removes the default Hello World! TextView, adds three Buttons aligned on a vertical chain, and a FragmentContainerView.
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<Button
android:id="@+id/button_toFragment1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/to_fragment_1"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<Button
android:id="@+id/button_toFragment2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/to_fragment_2"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/button_toFragment1" />
<Button
android:id="@+id/button_toFragment3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/to_fragment_3"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/button_toFragment2" />
<androidx.fragment.app.FragmentContainerView
android:id="@+id/fragmentContainerView"
android:name="com.codelab.daniwebhiltviewmodels.BlankFragment1"
android:layout_width="match_parent"
android:layout_height="0dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@id/button_toFragment3" />
</androidx.constraintlayout.widget.ConstraintLayout>Add the code below into MainActivity#onCreate(). It binds the three buttons to an action that will always create the respective Fragment, without any backstack.
val toFragment1Button = findViewById<Button>(R.id.button_toFragment1)
val toFragment2Button = findViewById<Button>(R.id.button_toFragment2)
val toFragment3Button = findViewById<Button>(R.id.button_toFragment3)
toFragment1Button.setOnClickListener{
supportFragmentManager.commit {
replace<BlankFragment1>(R.id.fragmentContainerView)
}
}
toFragment2Button.setOnClickListener {
supportFragmentManager.commit {
replace<BlankFragment2>(R.id.fragmentContainerView)
}
}
toFragment3Button.setOnClickListener {
supportFragmentManager.commit {
replace<BlankFragment3>(R.id.fragmentContainerView)
}
}Annotate MainActivity and all three Fragment classes with @AndroidEntryPoint.
Add the <string> resources below into your strings.xml.
<string name="to_fragment_1">To Fragment 1</string>
<string name="to_fragment_2">To Fragment 2</string>
<string name="to_fragment_3">To Fragment 3</string>
<string name="hello_blank_fragment">Hello blank fragment</string>
<string name="hello_blank_fragment2">Hello blank fragment2</string>
<string name="hello_blank_fragment3">Hello blank fragment3</string>Go to each Fragments associated layout XML and modify the default TextViews android:text to the respective <string> resource above.
Properly tag each Fragment with BLANK_FRAGMENT_X, respectively.
Add the dependency below into your Project build.gradle.
buildscript {
dependencies {
classpath 'com.google.dagger:hilt-android-gradle-plugin:2.40.5'
}
}Add the plugins for kapt and hilt to your Module build.gradle.
implementation "com.google.dagger:hilt-android:2.40.5"
implementation "androidx.fragment:fragment-ktx:1.4.1"
kapt "com.google.dagger:hilt-compiler:2.40.5"Also in the Module build.gradle, add the dependencies below.
implementation "com.google.dagger:hilt-android:2.40.5"
kapt "com.google.dagger:hilt-compiler:2.40.5"Create the required Application class for Hilt called MyApplication.kt.
import android.app.Application
import dagger.hilt.android.HiltAndroidApp
@HiltAndroidApp
class ExampleApplication : Application()Add the attribute below to the manifest <application> element.
android:name=".ExampleApplication"Our project so far includes three buttons, which will navigate to three different fragments. At the end of the tutorial, we should have created one ViewModel, which will be injected into the existing fragments. The lifecycle of the ViewModel will behave differently depending how it was injected, so we will observe the output from Logcat to understand what happens to the injected ViewModel instances.
First, let us create the ViewModel class FragmentViewModel. Copy and paste the code below into a new file named FragmentViewModel.kt.
private const val TAG = "FRAGMENT_VIEW_MODEL"
@HiltViewModel
class FragmentViewModel @Inject constructor(private val application: Application) : ViewModel() {
override fun onCleared() {
super.onCleared()
Log.d(TAG, "ViewModel ${hashCode()} is queued to be destroyed.")
}
}In the FragmentViewModel class above, the annotation @HiltViewModel tells Hilt that this ViewModel can be injected into other classes marked with @AndroidEntryPoint as well as allowing Hilt to inject other dependencies into this ViewModel. In this case, we have injected an Application class, which is a special pre-defined binding, only to show that Hilt will assist us in providing instances of this class by injecting this application dependency.
We have also overridden the onCleared() function. This function is called when the Android system destroys the ViewModel.
New Hilt ViewModels can be created and injected into each Fragment if requested. This means that each Fragment instance will receive different instances of ViewModel.
In BlankFragment1 and BlankFragment2, perform the steps below:
Add the fragmentViewModel member below. The viewModels() property delegate will provide a ViewModel scoped to the Fragment lifecycle. viewModels() is not only used with Hilt, but it can be used to provide simple ViewModel instances as well when not using Hilt.
private val fragmentViewModel: FragmentViewModel by viewModels()Append to onCreate() the code below. This will log when the Fragment is created and which ViewModel instance it receives.
Log.d(TAG, "Fragment ${hashCode()} is created with ViewModel ${fragmentViewModel.hashCode()} injected.")Override onDestroy() and append the code below. Leave the super() call as-is. This will log when the Fragment is destroyed. Shortly after the Fragment is destroyed, we should be able to see that the ViewModel calls its onClear() function as well.
Log.d(TAG, "Fragment ${hashCode()} is being destroyed.")While running the App with the Logcat filter BLANK_FRAGMENT|FRAGMENT_VIEW_MODEL in the Debug channel, we can see that the Fragment/ViewModel pair are being created and destroyed together (when you create another Fragment).
Hilt can also inject the same ViewModel instance to different instances of the same Fragment. We will apply this behavior to BlankFragment3.
viewModel() delegate with activityViewModel(). This will ensure that the ViewModel received is scoped to the Activitys lifecycle; this can mean the entire application lifecycle in many cases.When running the app and recreating BlankFragment3 multiple times, we can see that the same ViewModel instance is injected into multiple different instances of BlankFragment3.
MainActivity.kt
package com.codelab.daniwebhiltviewmodels
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Button
import androidx.fragment.app.commit
import androidx.fragment.app.replace
import dagger.hilt.android.AndroidEntryPoint
@AndroidEntryPoint
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val toFragment1Button = findViewById<Button>(R.id.button_toFragment1)
val toFragment2Button = findViewById<Button>(R.id.button_toFragment2)
val toFragment3Button = findViewById<Button>(R.id.button_toFragment3)
toFragment1Button.setOnClickListener{
supportFragmentManager.commit {
replace<BlankFragment1>(R.id.fragmentContainerView)
}
}
toFragment2Button.setOnClickListener {
supportFragmentManager.commit {
replace<BlankFragment2>(R.id.fragmentContainerView)
}
}
toFragment3Button.setOnClickListener {
supportFragmentManager.commit {
replace<BlankFragment3>(R.id.fragmentContainerView)
}
}
}
}FragmentViewModel.kt
package com.codelab.daniwebhiltviewmodels
import android.app.Application
import android.util.Log
import androidx.lifecycle.ViewModel
import dagger.hilt.android.lifecycle.HiltViewModel
import javax.inject.Inject
private const val TAG = "FRAGMENT_VIEW_MODEL"
@HiltViewModel
class FragmentViewModel @Inject constructor(private val application: Application) : ViewModel() {
override fun onCleared() {
super.onCleared()
Log.d(TAG, "ViewModel ${hashCode()} is queued to be destroyed.")
}
}BlankFragment1.kt
package com.codelab.daniwebhiltviewmodels
import android.os.Bundle
import android.util.Log
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.fragment.app.viewModels
import dagger.hilt.android.AndroidEntryPoint
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private const val ARG_PARAM1 = "param1"
private const val ARG_PARAM2 = "param2"
private const val TAG = "BLANK_FRAGMENT_1"
/**
* A simple [Fragment] subclass.
* Use the [BlankFragment1.newInstance] factory method to
* create an instance of this fragment.
*/
@AndroidEntryPoint
class BlankFragment1 : Fragment() {
// TODO: Rename and change types of parameters
private var param1: String? = null
private var param2: String? = null
private val fragmentViewModel: FragmentViewModel by viewModels()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
arguments?.let {
param1 = it.getString(ARG_PARAM1)
param2 = it.getString(ARG_PARAM2)
}
Log.d(TAG, "Fragment ${hashCode()} is created with ViewModel ${fragmentViewModel.hashCode()} injected.")
}
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
//Log.d(TAG, fragmentViewModel.toString())
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_blank1, container, false)
}
override fun onDestroy() {
super.onDestroy()
Log.d(TAG, "Fragment ${hashCode()} is being destroyed.")
}
companion object {
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* @param param1 Parameter 1.
* @param param2 Parameter 2.
* @return A new instance of fragment BlankFragment3.
*/
// TODO: Rename and change types and number of parameters
@JvmStatic
fun newInstance(param1: String, param2: String) =
BlankFragment1().apply {
arguments = Bundle().apply {
putString(ARG_PARAM1, param1)
putString(ARG_PARAM2, param2)
}
}
}
}BlankFragment2.kt
package com.codelab.daniwebhiltviewmodels
import android.os.Bundle
import android.util.Log
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.fragment.app.viewModels
import dagger.hilt.android.AndroidEntryPoint
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private const val ARG_PARAM1 = "param1"
private const val ARG_PARAM2 = "param2"
private const val TAG = "BLANK_FRAGMENT_2"
/**
* A simple [Fragment] subclass.
* Use the [BlankFragment2.newInstance] factory method to
* create an instance of this fragment.
*/
@AndroidEntryPoint
class BlankFragment2 : Fragment() {
// TODO: Rename and change types of parameters
private var param1: String? = null
private var param2: String? = null
private val fragmentViewModel: FragmentViewModel by viewModels()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
arguments?.let {
param1 = it.getString(ARG_PARAM1)
param2 = it.getString(ARG_PARAM2)
}
Log.d(TAG, "Fragment ${hashCode()} is created with ViewModel ${fragmentViewModel.hashCode()} injected.")
}
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_blank2, container, false)
}
override fun onDestroy() {
super.onDestroy()
Log.d(TAG, "Fragment ${hashCode()} is being destroyed.")
}
companion object {
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* @param param1 Parameter 1.
* @param param2 Parameter 2.
* @return A new instance of fragment BlankFragment2.
*/
// TODO: Rename and change types and number of parameters
@JvmStatic
fun newInstance(param1: String, param2: String) =
BlankFragment2().apply {
arguments = Bundle().apply {
putString(ARG_PARAM1, param1)
putString(ARG_PARAM2, param2)
}
}
}
}BlankFragment3.kt
package com.codelab.daniwebhiltviewmodels
import android.os.Bundle
import android.util.Log
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.fragment.app.activityViewModels
import dagger.hilt.android.AndroidEntryPoint
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private const val ARG_PARAM1 = "param1"
private const val ARG_PARAM2 = "param2"
private const val TAG = "BLANK_FRAGMENT_3"
/**
* A simple [Fragment] subclass.
* Use the [BlankFragment3.newInstance] factory method to
* create an instance of this fragment.
*/
@AndroidEntryPoint
class BlankFragment3 : Fragment() {
// TODO: Rename and change types of parameters
private var param1: String? = null
private var param2: String? = null
private val fragmentViewModel: FragmentViewModel by activityViewModels()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
arguments?.let {
param1 = it.getString(ARG_PARAM1)
param2 = it.getString(ARG_PARAM2)
}
Log.d(TAG, "Fragment ${hashCode()} is created with ViewModel ${fragmentViewModel.hashCode()} injected.")
}
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_blank3, container, false)
}
override fun onDestroy() {
super.onDestroy()
Log.d(TAG, "Fragment ${hashCode()} is being destroyed.")
}
companion object {
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* @param param1 Parameter 1.
* @param param2 Parameter 2.
* @return A new instance of fragment BlankFragment3.
*/
// TODO: Rename and change types and number of parameters
@JvmStatic
fun newInstance(param1: String, param2: String) =
BlankFragment3().apply {
arguments = Bundle().apply {
putString(ARG_PARAM1, param1)
putString(ARG_PARAM2, param2)
}
}
}
}MyApplication.kt
package com.codelab.daniwebhiltviewmodels
import android.app.Application
import dagger.hilt.android.HiltAndroidApp
@HiltAndroidApp
class ExampleApplication : Application()
**activity_main.xml**
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<Button
android:id="@+id/button_toFragment1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/to_fragment_1"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<Button
android:id="@+id/button_toFragment2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/to_fragment_2"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/button_toFragment1" />
<Button
android:id="@+id/button_toFragment3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/to_fragment_3"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/button_toFragment2" />
<androidx.fragment.app.FragmentContainerView
android:id="@+id/fragmentContainerView"
android:name="com.codelab.daniwebhiltviewmodels.BlankFragment1"
android:layout_width="match_parent"
android:layout_height="0dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@id/button_toFragment3" />
</androidx.constraintlayout.widget.ConstraintLayout>fragment_blank_1.xml
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".BlankFragment1">
<!-- TODO: Update blank fragment layout -->
<TextView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:text="@string/hello_blank_fragment" />
</FrameLayout>fragment_blank_2.xml
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".BlankFragment2">
<!-- TODO: Update blank fragment layout -->
<TextView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:text="@string/hello_blank_fragment2" />
</FrameLayout>fragment_blank_3.xml
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".BlankFragment3">
<!-- TODO: Update blank fragment layout -->
<TextView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:text="@string/hello_blank_fragment3" />
</FrameLayout>strings.xml
<resources>
<string name="app_name">Daniweb Hilt ViewModels</string>
<string name="to_fragment_1">To Fragment 1</string>
<string name="to_fragment_2">To Fragment 2</string>
<string name="to_fragment_3">To Fragment 3</string>
<string name="hello_blank_fragment">Hello blank fragment</string>
<string name="hello_blank_fragment2">Hello blank fragment2</string>
<string name="hello_blank_fragment3">Hello blank fragment3</string>
</resources>Project build.gradle
buildscript {
dependencies {
classpath 'com.google.dagger:hilt-android-gradle-plugin:2.40.5'
}
}
// Top-level build file where you can add configuration options common to all sub-projects/modules.
plugins {
id 'com.android.application' version '7.1.1' apply false
id 'com.android.library' version '7.1.1' apply false
id 'org.jetbrains.kotlin.android' version '1.6.10' apply false
}
task clean(type: Delete) {
delete rootProject.buildDir
}Module build.gradle
plugins {
id 'com.android.application'
id 'org.jetbrains.kotlin.android'
id 'kotlin-kapt'
id 'dagger.hilt.android.plugin'
}
android {
compileSdk 32
defaultConfig {
applicationId "com.codelab.daniwebhiltviewmodels"
minSdk 21
targetSdk 32
versionCode 1
versionName "1.0"
testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
}
}
compileOptions {
sourceCompatibility JavaVersion.VERSION_1_8
targetCompatibility JavaVersion.VERSION_1_8
}
kotlinOptions {
jvmTarget = '1.8'
}
}
dependencies {
implementation "com.google.dagger:hilt-android:2.40.5"
implementation "androidx.fragment:fragment-ktx:1.4.1"
kapt "com.google.dagger:hilt-compiler:2.40.5"
implementation 'androidx.legacy:legacy-support-v4:1.0.0'
implementation 'androidx.core:core-ktx:1.7.0'
implementation 'androidx.appcompat:appcompat:1.4.1'
implementation 'com.google.android.material:material:1.5.0'
implementation 'androidx.constraintlayout:constraintlayout:2.1.3'
testImplementation 'junit:junit:4.13.2'
androidTestImplementation 'androidx.test.ext:junit:1.1.3'
androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
}AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.codelab.daniwebhiltviewmodels">
<application
android:name=".ExampleApplication"
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/Theme.DaniwebHiltViewModels">
<activity
android:name=".MainActivity"
android:exported="true">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>We have learned how to inject ViewModels with Hilt in this tutorial. The full project code can be found at https://github.com/dmitrilc/DaniwebHiltViewModels
In Android development, reusable layouts can be used to reduce duplicate code across XML files. In this tutorial, we will learn how to reuse layout files, especially with View Binding enabled.
At the end of the tutorial, you would have learned:
To follow along with the tutorial, perform the steps below:
Create a new Android project with the default Empty Activity.
Give the default Hello World! TextView an android:id of textView_default.
Create another layout resource file called reusable_layout.xml. Copy and paste the code below to replace all of the content of this file. This code removes the default ConstraintLayout because it is not necessary for our use case. It also adds a TextView with an id.
<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/textView_reusable"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="TextView" />Enable View Binding in the Module gradle.build file, inside of the android {} tag. This will instruct the compiler to generate Binding classes at development time.
buildFeatures {
viewBinding true
}Add the binding to activity_main.xml in MainActivity with the code below.
private lateinit var binding: ActivityMainBindingReplace the current onCreate() call with the code below. We now inflate the layout using View Binding instead of R.id.
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityMainBinding.inflate(layoutInflater)
setContentView(binding.root)
}Currently, our project is a simple app with a Hello World! TextView. The presentation of the app is not the focus of the tutorial though. At the end of the tutorial, we would be able to reuse the reusable_layout.xml in activitiy_main.xml and referencing it with View Binding as well.
To reuse a layout, we only need to do two things:
<include> tag where the reusable layout would normally be placed.Let us do this now for our project.
Open activity_main.xml.
Add the <include> tag below <TextView>.
<include/>Give the <include> tag a layout attribute, with its value being the path to the reusable layout.
<include
layout="@layout/reusable_layout"/>The reusable layout would now show up in the Design surface as well.
But there are two new problems: the included View is not constrained at all and the compiler does not provide any error. Normally, a child view of ConstraintLayout is required to have constraints. It seems like the compiler does not throw an error for missing constraints in child views added via <include>, so there is nothing that we can do about it. Fortunately, if we select the <include> tag in the Component Tree and open its Attributes panel, we can at least see that the ConstraintLayout expects the child to have constraints, so at least we should add the constraints by ourselves.
Replace the current <include> with the code below. This will add constraints to the included layout and situate it under the default TextView. Everytime that you override any layout_x attribute of an <include> tag, you must also override both <layout_width> and <layout_height> attributes. Because we have overridden <layout_constraintX> attributes, we are required to override <layout_width> and <layout_height> as well, even if that means duplicating code already declared in the reusable layout.
<include
layout="@layout/reusable_layout"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@id/textView_default" />Select the <include> tag again with the Attributes panel opened and we should see the warnings cleared out.
As of right now, our project is unable to reference the child textView_reusable from the parent View Binding.
For the compiler to generate Binding classes, we simply provide <include> with an id of our choice.
android:id="@+id/include"We should be able to reference the child view immediately via include. If you do not see it showing up, you might need to clean and rebuild your project.
Our project depends on the compiler to generate Binding classes. If you do not see generated Binding classes after running Gradle tasks Clean and Rebuild, you should check whether you are running the latest version of Gradle and if it works with the AGP version. The AGP version used in this project is 7.1.1 and Gradle version is 7.3.3.
When running the app, we can see that it is working correctly.
MainActivity.kt
package com.codelab.daniwebreusablelayoutsandviewbinding
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import com.codelab.daniwebreusablelayoutsandviewbinding.databinding.ActivityMainBinding
class MainActivity : AppCompatActivity() {
private lateinit var binding: ActivityMainBinding
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityMainBinding.inflate(layoutInflater)
setContentView(binding.root)
binding.include.textViewReusable.text = "Replaced Text"
}
}activitiy_main.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<TextView
android:id="@+id/textView_default"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Hello World!"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<include
android:id="@+id/include"
layout="@layout/reusable_layout"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@id/textView_default" />
</androidx.constraintlayout.widget.ConstraintLayout>reusable_layout.xml
<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/textView_reusable"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="TextView" />Module build.gradle
plugins {
id 'com.android.application'
id 'org.jetbrains.kotlin.android'
}
android {
compileSdk 32
buildFeatures {
viewBinding true
}
defaultConfig {
applicationId "com.codelab.daniwebreusablelayoutsandviewbinding"
minSdk 21
targetSdk 32
versionCode 1
versionName "1.0"
testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
}
}
compileOptions {
sourceCompatibility JavaVersion.VERSION_1_8
targetCompatibility JavaVersion.VERSION_1_8
}
kotlinOptions {
jvmTarget = '1.8'
}
}
dependencies {
implementation 'androidx.core:core-ktx:1.7.0'
implementation 'androidx.appcompat:appcompat:1.4.1'
implementation 'com.google.android.material:material:1.5.0'
implementation 'androidx.constraintlayout:constraintlayout:2.1.3'
testImplementation 'junit:junit:4.13.2'
androidTestImplementation 'androidx.test.ext:junit:1.1.3'
androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
}We have learned how to reuse layouts and referencing them via View Binding as well. The full project code can be found at https://github.com/dmitrilc/DaniwebReusableLayoutsAndViewBinding
hi there i have a python http post request with no request but theres the code:
requests.post("https://api.i66v1xg2.org/v3/moderate/+" + userid + "/")
i dont know how to make it in java and in okhttp3 help pls thanks
MediaPlayer (android.media.MediaPlayer) is a popular way to play media files, and combining it with a SeekBar can greatly improve the user experience. In this tutorial, we will learn how to synchronize a MediaPlayer progress to a SeekBar position.
At the end of the tutorial, you would have learned:
To follow along with the tutorial, perform the steps below:
Create a new Android project with the default Empty Activity.
Give the default Hello World! TextView android:id of textView_time.
Completely remove the android:text attribute from textView_time.
Add the tools:text attribute to textView_time with the value of 0:00.
Add the android:textSize attribute with the value of 32sp.
Constraint textView_time to the top, start, and end of ConstraintLayout, but leave the bottom side unconstrained.
Your textView_time should look like the code below.
<TextView
android:id="@+id/textView_time"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="32sp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
tools:text="0.00" />Download the .mp3 file called Unexpected Gifts of Spring by Alextree from the FreeMusicArchive. This song is licensed under CC BY 4.0. You are recommended to download the file from the AVDs built-in web browser. If you have downloaded the file to your development machine, you can also drag and drop the file into the AVDs via the Device File Explorer, which will trigger a download action on the AVD (this behavior has only been tested on a Windows machine, I am not sure if this works on a Mac/Linux). Getting the files using these methods will automatically add an entry into the MediaStore.
Add the LifecycleScope KTX extension to your module build.gradle file.
implementation 'androidx.lifecycle:lifecycle-runtime-ktx:2.4.0'SeekBar is a built-in Android View, which extends ProgressBar. It contains a draggable circle that end users can drag to specific points on a timeline.
Perform the steps below to add a SeekBar into the project.
Open activity_main.xml in the Code view.
Copy and paste the code below into activity_main.xml.
<SeekBar
android:id="@+id/seekBar"
android:layout_width="match_parent"
android:layout_height="64dp"
android:layout_marginHorizontal="16dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@id/textView_time" />Alternatively, if you prefer to configure your own SeekBar from scratch, it can also be found at Palette > Widgets, in the Design view.
Now, add these attributes below into textView_time to finish creating a vertical chain for the two Views.
app:layout_constraintBottom_toTopOf="@id/seekBar"
app:layout_constraintHorizontal_bias="0.5"We will need to reference these Views later, so append these lines of code to MainActivity#onCreate().
//Gets the textView_time reference
val timeView = findViewById<TextView>(R.id.textView_time)
//Gets the seekBar reference
val seekBar = findViewById<SeekBar>(R.id.seekBar)The next thing that we need in our project is a way to open the mp3 file that we downloaded earlier. We will use SAF/ActivityResult APIs for this.
Append the code below to MainActivity#onCreate().
//Launcher to open file with a huge callback. Organize in real code.
val openMusicLauncher = registerForActivityResult(OpenDocument()){ uri ->
}
val mimeTypes = arrayOf("audio/mpeg")
openMusicLauncher.launch(mimeTypes)The code snippet above will start a Content Picker UI for the end user to pick a file matching the specified mime type. The chosen mime type of audio/mpeg will match .mp3 files, according to this Common MIME Types list.
Now, we need to add a MediaPlayer object into our App for playing music files. To add MediaPlayer into our code, follow the steps below:
It is recommended to call MediaPlayer#release() to release resources when you are done with it, so we will add a reference to the MediaPlayer as a class property, for easy access in multiple callbacks such as onPause(), onStop(), onDestroy().
//Keeps a reference here to make it easy to release later
private var mediaPlayer: MediaPlayer? = nullOverride MainActivity#onStop() to release and null out mediaPlayer.
override fun onStop() {
super.onStop()
mediaPlayer?.release()
mediaPlayer = null
}Inside the openMusicLauncher callback, instantiate a MediaPlayer using the factory function MediaPlayer#create() and assign it to mediaPlayer.
mediaPlayer = MediaPlayer.create(applicationContext, uri)Since mediaPlayer is nullable, we will chain the newly created MediaPlayer with an also {} scope function block to skip multiple null checks in the next few steps.
mediaPlayer = MediaPlayer.create(applicationContext, uri)
.also { //also {} scope function skips multiple null checks
}The SeekBar that the end user sees on the screen must scale relatively with the duration of the media file.
So we will have to set the SeekBar max value corresponding to the file duration. Inside the also {} block, add the code below.
seekBar.max = it.durationNow, start() the MediaPlayer.
it.start()Launch a coroutine running the Main thread with the code below.
//Should be safe to use this coroutine to access MediaPlayer (not thread-safe)
//because it uses MainCoroutineDispatcher by default
lifecycleScope.launch {
}
//Can also release mediaPlayer here, if not looping.
}Inside of launch {}, add a while() loop conditioned to the Boolean MediaPlayer.isPlaying.
//Should be safe to use this coroutine to access MediaPlayer (not thread-safe)
//because it uses MainCoroutineDispatcher by default
lifecycleScope.launch {
while (it.isPlaying){
}
//Can also release mediaPlayer here, if not looping.
}Inside of this while() loop, we can synchronize SeekBar#progress with MediaPlayer.currentPosition.
lifecycleScope.launch {
while (it.isPlaying){
seekBar.progress = it.currentPosition
}
//Can also release mediaPlayer here, if not looping.
}We can also synchronize TextView#text with MediaPlayer.currentPosition. The milliseconds extension property of Int is used here for convenience because its default toString() form is quite readable (you will see later). Time-formatting is not the focus of this tutorial.
//Should be safe to use this coroutine to access MediaPlayer (not thread-safe)
//because it uses MainCoroutineDispatcher by default
lifecycleScope.launch {
while (it.isPlaying){
seekBar.progress = it.currentPosition
timeView.text = "${it.currentPosition.milliseconds}"
}
//Can also release mediaPlayer here, if not looping.
}Finally, add a delay() to the coroutine. This ensures that the seekBar will only update every one second.
lifecycleScope.launch {
while (it.isPlaying){
seekBar.progress = it.currentPosition
timeView.text = "${it.currentPosition.milliseconds}"
delay(1000)
}
//Can also release mediaPlayer here, if not looping.
}The code that we have so far will only update the SeekBar position and TextView content to the MediaPlayer progress. We will have to add a SeekBar.OnSeekBarChangeListener object to the SeekBar to monitor for changes. Follow the steps below to complete the tutorial.
Append the object below to the openMusicLauncher callback. We have only implemented onProgressChanged because that is all we need for now. We also used the function MediaPlayer#seekTo() to seek a specified time position.
//Move this object somewhere else in real code
val seekBarListener = object : SeekBar.OnSeekBarChangeListener {
override fun onProgressChanged(seekBar: SeekBar?, progress: Int, fromUser: Boolean) {
if (fromUser){
//sets the playing file progress to the same seekbar progressive, in relative scale
mediaPlayer?.seekTo(progress)
//Also updates the textView because the coroutine only runs every 1 second
timeView.text = "${progress.milliseconds}"
}
}
override fun onStartTrackingTouch(seekBar: SeekBar?) {}
override fun onStopTrackingTouch(seekBar: SeekBar?) {}
}Now, assign seekBarLisenter to seekBar.
seekBar.setOnSeekBarChangeListener(seekBarListener)We are now ready to launch the App. Your App should behave similarly to the Gif below. You can ignore the other files in my AVDs Downloads directory that are not part of the project setup.
build.gradle
plugins {
id 'com.android.application'
id 'org.jetbrains.kotlin.android'
}
android {
compileSdk 31
defaultConfig {
applicationId "com.codelab.daniwebandroidaudioseekbarsync"
minSdk 21
targetSdk 31
versionCode 1
versionName "1.0"
testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
}
}
compileOptions {
sourceCompatibility JavaVersion.VERSION_1_8
targetCompatibility JavaVersion.VERSION_1_8
}
kotlinOptions {
jvmTarget = '1.8'
}
}
dependencies {
implementation 'androidx.lifecycle:lifecycle-runtime-ktx:2.4.0'
implementation 'androidx.core:core-ktx:1.7.0'
implementation 'androidx.appcompat:appcompat:1.4.1'
implementation 'com.google.android.material:material:1.5.0'
implementation 'androidx.constraintlayout:constraintlayout:2.1.3'
testImplementation 'junit:junit:4.13.2'
androidTestImplementation 'androidx.test.ext:junit:1.1.3'
androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
}activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<TextView
android:id="@+id/textView_time"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="32sp"
app:layout_constraintBottom_toTopOf="@id/seekBar"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
tools:text="0.00" />
<SeekBar
android:id="@+id/seekBar"
android:layout_width="match_parent"
android:layout_height="64dp"
android:layout_marginHorizontal="16dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@id/textView_time" />
</androidx.constraintlayout.widget.ConstraintLayout>MainActivity.kt
package com.codelab.daniwebandroidaudioseekbarsync
import android.media.MediaPlayer
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.SeekBar
import android.widget.TextView
import androidx.activity.result.contract.ActivityResultContracts.OpenDocument
import androidx.lifecycle.lifecycleScope
import kotlinx.coroutines.delay
import kotlinx.coroutines.launch
import kotlin.time.Duration.Companion.milliseconds
class MainActivity : AppCompatActivity() {
//Keeps a reference here to make it easy to release later
private var mediaPlayer: MediaPlayer? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
//Gets the textView_time reference
val timeView = findViewById<TextView>(R.id.textView_time)
//Gets the seekBar reference
val seekBar = findViewById<SeekBar>(R.id.seekBar)
//Launcher to open file with a huge callback. Organize in real code.
val openMusicLauncher = registerForActivityResult(OpenDocument()){ uri ->
//Instantiates a MediaPlayer here now that we have the Uri.
mediaPlayer = MediaPlayer.create(applicationContext, uri)
.also { //also {} scope function skips multiple null checks
seekBar.max = it.duration
it.start()
//Should be safe to use this coroutine to access MediaPlayer (not thread-safe)
//because it uses MainCoroutineDispatcher by default
lifecycleScope.launch {
while (it.isPlaying){
seekBar.progress = it.currentPosition
timeView.text = "${it.currentPosition.milliseconds}"
delay(1000)
}
//Can also release mediaPlayer here, if not looping.
}
}
//Move this object somewhere else in real code
val seekBarListener = object : SeekBar.OnSeekBarChangeListener {
override fun onProgressChanged(seekBar: SeekBar?, progress: Int, fromUser: Boolean) {
if (fromUser){
//sets the playing file progress to the same seekbar progressive, in relative scale
mediaPlayer?.seekTo(progress)
//Also updates the textView because the coroutine only runs every 1 second
timeView.text = "${progress.milliseconds}"
}
}
override fun onStartTrackingTouch(seekBar: SeekBar?) {}
override fun onStopTrackingTouch(seekBar: SeekBar?) {}
}
seekBar.setOnSeekBarChangeListener(seekBarListener)
}
val mimeTypes = arrayOf("audio/mpeg")
openMusicLauncher.launch(mimeTypes)
}
override fun onStop() {
super.onStop()
mediaPlayer?.release()
mediaPlayer = null
}
}Congrations, you have learned how to sync a MediaPlayer and a SeekBar. The full project code can be found at https://github.com/dmitrilc/DaniwebAndroidAudioSeekbarSync.
In my hometown, I'm a budding entrepreneur with a cab business that I'd want to develop to meet current market demands. It would be more expensive to create a mobile app for both iOS and Android. As a result, I resorted to Android to build my own taxi booking application. Is there anyone who can help me come up with a nice idea for it? Should I rely on ready-made mobile apps on the market?
I'm simply looking for the most basic essential features right now, with the goal of eventually updating my app solution to include additional critical functions and a more appealing user experience.
When working with a Room database, we are mostly restricted to save data using primitives (and boxed primitives). Reference types are not supported right out of the box, but can be enabled by creating additional TypeConverter. If you are familiar with ORM-light frameworks such as Spring JDBC, then you can think of TypeConverters as being conceptually similar to RowMapper.
In this tutorial, we will learn how to use TypeConverters in a Room database. Existing basic knowledge of Room is required for this tutorial.
At the end of the tutorial, you would have learned:
To follow along with the tutorial, perform the steps below:
Create a new Android project with the default Empty Activity.
Add the dependencies below into your Module build.gradle file inside the dependencies {} block.
def roomVersion = "2.4.1"
implementation "androidx.room:room-runtime:$roomVersion"
annotationProcessor "androidx.room:room-compiler:$roomVersion"
//To use Kotlin annotation processing tool (kapt)
kapt "androidx.room:room-compiler:$roomVersion"
//Kotlin Extensions and Coroutines support for Room
implementation "androidx.room:room-ktx:$roomVersion"
//lifecycle scope
implementation 'androidx.lifecycle:lifecycle-runtime-ktx:2.4.1'In the same file, add the kapt annotation processor inside the plugins {} block.
id 'org.jetbrains.kotlin.kapt'Create a new file called Teacher.kt and add the code below.
data class Teacher(
val name: String,
val age: Int
) {
override fun toString(): String {
return "$name:$age"
}
}Create a new file called Classroom.kt and add the code below.
import androidx.room.ColumnInfo
import androidx.room.Entity
import androidx.room.PrimaryKey
@Entity
data class Classroom(
@PrimaryKey(autoGenerate = true) val uid: Int = 0,
val grade: Grade,
@ColumnInfo(name = "homeroom_teacher") val homeroomTeacher: Teacher
)Create a new file called ClassroomDao.kt and add the code below.
import androidx.room.*
@Dao
interface ClassroomDao {
@Query("SELECT * FROM classroom")
fun getAll(): List<Classroom>
@Insert(onConflict = OnConflictStrategy.REPLACE)
fun insertAll(vararg classrooms: Classroom)
}Create a new file called Grade.kt and add the code below.
enum class Grade {
JUNIOR, SOPHOMORE, SENIOR
}Create a new file called SchoolDatabase.kt and add the code below.
import androidx.room.BuiltInTypeConverters
import androidx.room.Database
import androidx.room.RoomDatabase
import androidx.room.TypeConverters
@Database(entities = [Classroom::class], version = 1)
//@TypeConverters(
// Converters::class,
// builtInTypeConverters = BuiltInTypeConverters(
// enums = BuiltInTypeConverters.State.DISABLED
// )
//)
abstract class SchoolDatabase : RoomDatabase() {
abstract fun classroomDao(): ClassroomDao
}Create a new file called Converters.kt and add the code below.
package com.codelab.daniwebandroidroomdatabaseconverter
import androidx.room.TypeConverter
class Converters {
@TypeConverter
fun teacherToString(teacher: Teacher) = "$teacher" //Other options are json string, serialized blob
@TypeConverter
fun stringToTeacher(value: String): Teacher {
val name = value.substringBefore(':')
val age = value.substringAfter(':').toInt()
return Teacher(name, age)
}
}Our skeleton project for this tutorial is quite simple. We completely ignore the UI, ViewModel or Hilt DI to focus on the database here. The Room database SchoolDatabase includes a single table that stores classroom information. Each classroom contains an id, the Grade, and a Teacher.
Because Teacher is a reference type, so Room will refuse to compile for now. Upon compiling, we will receive the error messages below.
error: Cannot figure out how to save this field into database. You can consider adding a type converter for it.
error: Cannot figure out how to save this field into database. You can consider adding a type converter for it.
private final com.codelab.daniwebandroidroomdatabaseconverter.Teacher homeroomTeacher = null;
error: Cannot figure out how to read this field from a cursor.
private final com.codelab.daniwebandroidroomdatabaseconverter.Teacher homeroomTeacher = null;These errors occur because we have not registered any TypeConverter to our SchoolDatabase.
To help Room understand how to convert these reference types, we will have to create TypeConverters. TypeConverters can only be used to convert a column. In the the picture below, a TypeConverter pair can be used to convert a column into a primitive that Room allows, and vice versa.
TypeConverters are just functions annotated with @TypeConverter. We have already created some TypeConverters in the file Converters.kt, so let us inspect some of them.
The first function that we are going to look at is teacherToString().
@TypeConverter
fun teacherToString(teacher: Teacher) = "$teacher" //Other options are json string, serialized blobIn teacherToString(), the only three things that really matter for Room are the parameter type, the return type, and the @TypeConverter annotation. The compiler uses information from them to determine whether Room can properly use them to convert from one type to another. The parameter type and the return type are reversed when it comes to stringToTeacher().
@TypeConverter
fun stringToTeacher(value: String): Teacher {
val name = value.substringBefore(':')
val age = value.substringAfter(':').toInt()
return Teacher(name, age)
}
I have decided to store a string representation of a Teacher object in this tutorial because it is quick and simple. I have also overridden Teachers toString() to make the deserialization easier.
override fun toString(): String {
return "$name:$age"
}In real code, you can store your object in other ways, such as a serialized BLOB or a JSON string, with proper sanitization.
You might have noticed that I have not discussed the Grade enum at all. It is, after all, also a reference type. The simple reason why we do not have to provide TypeConverters for Grade is because Android already includes some premade TypeConverters from BuiltInTypeConverters.
Enums and UUID types are supported by default. The default support for enum uses the name() value. If that is not good enough for you, then you can also provide custom TypeConverters for Enum and UUID. Your custom TypeConverters take precedence over the builtin ones.
The next step that we would need to do is to register the Converters with the database. You can do that by applying an @Converters annotation to the RoomDatabase class. Note that @Converter and @Converters are different annotations. We already have the @TypeConverters annotation set up in SchoolDatabase.kt, but commented out. Uncomment it, and we will have the code below.
@TypeConverters(
Converters::class,
builtInTypeConverters = BuiltInTypeConverters(
enums = BuiltInTypeConverters.State.DISABLED
)
)The builtInTypeConverters argument is entirely optional. If you do not provide it any value, then it will enable the default TypeConverters. If we run the App now, we will receive a compile error of:
error: Cannot figure out how to save this field into database. You can consider adding a type converter for it.
private final com.codelab.daniwebandroidroomdatabaseconverter.Grade grade = null;This is because we have told Room to disable the builtin TypeConverter for enums. We also did not provide any custom enum TypeConverter. Simply comment out the builtInTypeConverters argument for the code to compile.
@TypeConverters(
Converters::class
/* builtInTypeConverters = BuiltInTypeConverters(
enums = BuiltInTypeConverters.State.DISABLED
)*/
)The Class object that we provided indicates that this class contains the @TypeConverter functions, so Room should look there for any type that it does not know how to convert.
The app should compile correctly now, but it does not do anything useful yet.
Add the top level variable below into MainActivity.kt.
private const val TAG = "MAIN_ACTIVITY"Append the code below to MainActivity#onCreate().
val db = Room.databaseBuilder(
applicationContext,
SchoolDatabase::class.java, "school-db"
).build()
lifecycleScope.launch(Dispatchers.IO) {
val classroomDao = db.classroomDao()
val teacher1 = Teacher(
name = "Mary",
age = 35
)
val teacher2 = Teacher(
name = "John",
age = 28
)
val teacher3 = Teacher(
name = "Diana",
age = 46
)
val classroom1 = Classroom(
grade = Grade.JUNIOR,
homeroomTeacher = teacher1
)
val classroom2 = Classroom(
grade = Grade.SOPHOMORE,
homeroomTeacher = teacher2
)
val classroom3 = Classroom(
grade = Grade.SENIOR,
homeroomTeacher = teacher3
)
classroomDao.insertAll(
classroom1,
classroom2,
classroom3
)
val classrooms = classroomDao.getAll()
classrooms.forEach {
Log.d(TAG, "$it")
}
db.clearAllTables()
}Run the app now. We should be able to see the output below in Logcat.
2022-02-14 13:59:18.700 12504-12551/com.codelab.daniwebandroidroomdatabaseconverter D/MAIN_ACTIVITY: Classroom(uid=1, grade=JUNIOR, homeroomTeacher=Mary:35)
2022-02-14 13:59:18.700 12504-12551/com.codelab.daniwebandroidroomdatabaseconverter D/MAIN_ACTIVITY: Classroom(uid=2, grade=SOPHOMORE, homeroomTeacher=John:28)
2022-02-14 13:59:18.701 12504-12551/com.codelab.daniwebandroidroomdatabaseconverter D/MAIN_ACTIVITY: Classroom(uid=3, grade=SENIOR, homeroomTeacher=Diana:46)MainActivity.kt
package com.codelab.daniwebandroidroomdatabaseconverter
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.util.Log
import androidx.lifecycle.lifecycleScope
import androidx.room.Room
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.launch
private const val TAG = "MAIN_ACTIVITY"
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val db = Room.databaseBuilder(
applicationContext,
SchoolDatabase::class.java, "school-db"
).build()
lifecycleScope.launch(Dispatchers.IO) {
val classroomDao = db.classroomDao()
val teacher1 = Teacher(
name = "Mary",
age = 35
)
val teacher2 = Teacher(
name = "John",
age = 28
)
val teacher3 = Teacher(
name = "Diana",
age = 46
)
val classroom1 = Classroom(
grade = Grade.JUNIOR,
homeroomTeacher = teacher1
)
val classroom2 = Classroom(
grade = Grade.SOPHOMORE,
homeroomTeacher = teacher2
)
val classroom3 = Classroom(
grade = Grade.SENIOR,
homeroomTeacher = teacher3
)
classroomDao.insertAll(
classroom1,
classroom2,
classroom3
)
val classrooms = classroomDao.getAll()
classrooms.forEach {
Log.d(TAG, "$it")
}
db.clearAllTables()
}
}
}Classroom.kt
package com.codelab.daniwebandroidroomdatabaseconverter
import androidx.room.ColumnInfo
import androidx.room.Entity
import androidx.room.PrimaryKey
@Entity
data class Classroom(
@PrimaryKey(autoGenerate = true) val uid: Int = 0,
val grade: Grade,
@ColumnInfo(name = "homeroom_teacher") val homeroomTeacher: Teacher
)ClassroomDao
package com.codelab.daniwebandroidroomdatabaseconverter
import androidx.room.*
@Dao
interface ClassroomDao {
@Query("SELECT * FROM classroom")
fun getAll(): List<Classroom>
@Insert(onConflict = OnConflictStrategy.REPLACE)
fun insertAll(vararg classrooms: Classroom)
}Converters.kt
package com.codelab.daniwebandroidroomdatabaseconverter
import androidx.room.TypeConverter
class Converters {
@TypeConverter
fun teacherToString(teacher: Teacher) = "$teacher" //Other options are json string, serialized blob
@TypeConverter
fun stringToTeacher(value: String): Teacher {
val name = value.substringBefore(':')
val age = value.substringAfter(':').toInt()
return Teacher(name, age)
}
}Grade.kt
package com.codelab.daniwebandroidroomdatabaseconverter
enum class Grade {
JUNIOR, SOPHOMORE, SENIOR
}
**SchoolDatabase.kt**
package com.codelab.daniwebandroidroomdatabaseconverter
import androidx.room.BuiltInTypeConverters
import androidx.room.Database
import androidx.room.RoomDatabase
import androidx.room.TypeConverters
@Database(entities = [Classroom::class], version = 1)
@TypeConverters(
Converters::class
/* builtInTypeConverters = BuiltInTypeConverters(
enums = BuiltInTypeConverters.State.DISABLED
)*/
)
abstract class SchoolDatabase : RoomDatabase() {
abstract fun classroomDao(): ClassroomDao
}Teacher.kt
package com.codelab.daniwebandroidroomdatabaseconverter
data class Teacher(
val name: String,
val age: Int
) {
override fun toString(): String {
return "$name:$age"
}
}
Module **build.gradle**
plugins {
id 'com.android.application'
id 'org.jetbrains.kotlin.android'
id 'org.jetbrains.kotlin.kapt'
}
android {
compileSdk 32
defaultConfig {
applicationId "com.codelab.daniwebandroidroomdatabaseconverter"
minSdk 21
targetSdk 32
versionCode 1
versionName "1.0"
testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
}
}
compileOptions {
sourceCompatibility JavaVersion.VERSION_1_8
targetCompatibility JavaVersion.VERSION_1_8
}
kotlinOptions {
jvmTarget = '1.8'
}
}
dependencies {
def roomVersion = "2.4.1"
implementation "androidx.room:room-runtime:$roomVersion"
annotationProcessor "androidx.room:room-compiler:$roomVersion"
//To use Kotlin annotation processing tool (kapt)
kapt "androidx.room:room-compiler:$roomVersion"
//Kotlin Extensions and Coroutines support for Room
implementation "androidx.room:room-ktx:$roomVersion"
//lifecycle scope
implementation 'androidx.lifecycle:lifecycle-runtime-ktx:2.4.1'
implementation 'androidx.core:core-ktx:1.7.0'
implementation 'androidx.appcompat:appcompat:1.4.1'
implementation 'com.google.android.material:material:1.5.0'
implementation 'androidx.constraintlayout:constraintlayout:2.1.3'
testImplementation 'junit:junit:4.13.2'
androidTestImplementation 'androidx.test.ext:junit:1.1.3'
androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
}We have learned how to use TypeConverters in a Room database. The full project code can be found at https://github.com/dmitrilc/DaniwebAndroidRoomDatabaseConverter.
In this tutorial, we will learn how to add swipe-to-remove and drag-to-reorder functionalities into RecyclerView.
At the end of the tutorial, you would have learned:
To follow along with the tutorial, perform the steps below:
Create a new Android project with the default Empty Activity.
Replace the content of activity_main.xml with the code below.
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>Create a new layout resource called item_view.xml. This is the ViewHolders layout. Copy and paste the code below.
<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/itemView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="16dp"
android:gravity="center"
android:textSize="32sp"
tools:text="TextView" />Create a new Kotlin file called Item.kt. Copy and paste the code below.
data class Item(
val content: String
)Create a new Kotlin file called ItemAdapter.kt. Copy and paste the code below.
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import androidx.recyclerview.widget.RecyclerView
class ItemAdapter(private val dataset: List<Item>): RecyclerView.Adapter<ItemAdapter.ItemViewHolder>() {
class ItemViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView){
val textView: TextView = itemView.findViewById(R.id.itemView)
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ItemViewHolder {
val view = LayoutInflater.from(parent.context)
.inflate(R.layout.item_view, parent, false)
return ItemViewHolder(view)
}
override fun onBindViewHolder(holder: ItemViewHolder, position: Int) {
holder.textView.text = dataset[position].content
}
override fun getItemCount() = dataset.size
}In MainActivity#onCreate(), append the code below.
//Creates a list of 10 elements
val dataset = MutableList(10){
Item("I am Item #$it")
}
//finds the RecyclerView
val recyclerView = findViewById<RecyclerView>(R.id.recycler_view)
//Assigns an adapter to RecyclerView
recyclerView.adapter = ItemAdapter(dataset)Currently, our project will compile and run just fine. All we have at the moment is a vanilla recycler with 10 items. As you can see from the Gif below with the pointer tracking option on, our RecyclerView currently does not register swiping and hold-to-drag actions.
At the end of the tutorial, we should be able to swipe to remove and hold-to-drag-to-reorder the RecyclerView.
ItemTouchHelper is a class provided by Android specifically to implement the functionalities that we want. Its most basic properties are:
onMove() and onSwipe(), to decide what to do when swiping and dragging actions are recorded.The picture below provides a rough picture of the relationship among the classes. LEFT and RIGHT are not listed because START and END can perform the same thing for both LTR and RTL layouts.
There are about 3 things that we need to perform to implement swipe-to-remove and drag-to-move.
Follow the steps below to implement ItemTouchHelper.SimpleCallback.
Append the code below into MainActivity#onCreate(). Notice that we had to provide the bitwise or result of the direction constants.
//Implementing the callback.
val callback = object : ItemTouchHelper.SimpleCallback(
ItemTouchHelper.UP or ItemTouchHelper.DOWN, //bitwise OR
ItemTouchHelper.START or ItemTouchHelper.END //bitwise OR
) {
}We have not implemented the required members yet, so let us start with the first required, onMove(). This function determines what to do during drag-and-drop behaviors. All we had to do was to get the adapter positions of the ViewHolders and then call the notifyItemMoved() publisher. When the RecyclerView receives that signal, it will automatically reorder the items for us. It is optional to update the original dataset for our tutorial App.
override fun onMove(
recyclerView: RecyclerView,
viewHolder: RecyclerView.ViewHolder,
target: RecyclerView.ViewHolder
): Boolean {
val fromPosition = viewHolder.adapterPosition
val toPosition = target.adapterPosition
//modifying the dataset as well is optional for this tutorial
// val movedItem = dataset.removeAt(fromPosition)
// dataset.add(toPosition, movedItem)
//push specific event
recyclerView.adapter?.notifyItemMoved(fromPosition, toPosition)
return true
}Next, we will need to implement the other required member, onSwiped(). All we had to do was to remove the item at the requested position, and then call the notifyItemRemoved() publisher.
override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
val position = viewHolder.adapterPosition
//Actually removes the item from the dataset
dataset.removeAt(position)
//push specific event
recyclerView.adapter?.notifyItemRemoved(position)
}We only need two more lines of code before we can run the app.
Create the ItemTouchHelper object.
//Creates touch helper with callback
val touchHelper = ItemTouchHelper(callback)Attach it to the RecyclerView.
//attaches the helper to the recyclerView
touchHelper.attachToRecyclerView(recyclerView)Now, run the app. The swiping and dragging functions should work similarly to the Gif below.
MainActivity.kt
package com.codelab.daniwebrecyclerviewswipetoremove
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.recyclerview.widget.ItemTouchHelper
import androidx.recyclerview.widget.RecyclerView
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
//Creates a list of 10 elements
val dataset = MutableList(10){
Item("I am Item #$it")
}
//finds the RecyclerView
val recyclerView = findViewById<RecyclerView>(R.id.recycler_view)
//Assigns an adapter to RecyclerView
recyclerView.adapter = ItemAdapter(dataset)
//Implementing the callback.
val callback = object : ItemTouchHelper.SimpleCallback(
ItemTouchHelper.UP or ItemTouchHelper.DOWN, //bitwise OR
ItemTouchHelper.START or ItemTouchHelper.END //bitwise OR
) {
override fun onMove(
recyclerView: RecyclerView,
viewHolder: RecyclerView.ViewHolder,
target: RecyclerView.ViewHolder
): Boolean {
val fromPosition = viewHolder.adapterPosition
val toPosition = target.adapterPosition
//modifying the dataset as well is optional for this tutorial
// val movedItem = dataset.removeAt(fromPosition)
// dataset.add(toPosition, movedItem)
//push specific event
recyclerView.adapter?.notifyItemMoved(fromPosition, toPosition)
return true
}
override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
val position = viewHolder.adapterPosition
//Actually removes the item from the dataset
dataset.removeAt(position)
//push specific event
recyclerView.adapter?.notifyItemRemoved(position)
}
}
//Creates touch helper with callback
val touchHelper = ItemTouchHelper(callback)
//attaches the helper to the recyclerView
touchHelper.attachToRecyclerView(recyclerView)
}
}activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>item_view.xml
<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/itemView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="16dp"
android:gravity="center"
android:textSize="32sp"
tools:text="TextView" />Item.kt
package com.codelab.daniwebrecyclerviewswipetoremove
data class Item(
val content: String
)ItemAdapter.kt
package com.codelab.daniwebrecyclerviewswipetoremove
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import androidx.recyclerview.widget.RecyclerView
class ItemAdapter(private val dataset: List<Item>): RecyclerView.Adapter<ItemAdapter.ItemViewHolder>() {
class ItemViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView){
val textView: TextView = itemView.findViewById(R.id.itemView)
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ItemViewHolder {
val view = LayoutInflater.from(parent.context)
.inflate(R.layout.item_view, parent, false)
return ItemViewHolder(view)
}
override fun onBindViewHolder(holder: ItemViewHolder, position: Int) {
holder.textView.text = dataset[position].content
}
override fun getItemCount() = dataset.size
}We have learned how to add swipe-to-remove and drag-to-reorder in this tutorial. The full project code can be found at https://github.com/dmitrilc/DaniwebRecyclerViewSwipeToRemove.
When using Navigation Components, you might have wondered how to pass arguments between destinations. We will learn how to do just that in this tutorial. This tutorial also builds upon the Basic Navigation tutorial, so if you are not familiar with Navigation Components, I would recommend you to check it out.
There are two parts to this tutorial. First, we will learn how to perform navigation with type safety. Secondly, we will learn how to pass arguments with Safe Args.
At the end of the tutorial, you would have learned:
To follow along with the tutorial, perform the steps below:
Create a new Android project with the default Empty Activity.
Remove the default Hello World! TextView.
In the Project-level build.gradle file, add the buildscript{} block below. Make sure that you place it above the existing plugins{} block.
buildscript {
repositories {
google()
}
dependencies {
def nav_version = "2.4.0"
classpath "androidx.navigation:navigation-safe-args-gradle-plugin:$nav_version"
}
}In the Module-level build.gradle file, add the dependencies below to the dependencies{} block.
def nav_version = "2.4.0"
implementation "androidx.navigation:navigation-fragment-ktx:$nav_version"
implementation "androidx.navigation:navigation-ui-ktx:$nav_version"Also in the Module-level build.gradle file, add the plugin below into the plugins{} block.
id 'androidx.navigation.safeargs.kotlin'Because of this bug, you will have to downgrade your Android Gradle Plugin (AGP) to version 7.0.4. Gradle version 7.4 seems to work fine as of this tutorial. You can change your Project settings by going to File > Project Structure > Project.
Performs a Gradle sync.
In the same package as MainActivity.kt, create two new fragments called BlankFragment1.kt, BlankFragment2.kt along with their respective layout files fragment_blank1.xml and fragment_blank2.xml.
Create a new navigation graph called nav_graph.xml.
Replace the content of activity_main.xml with the code below.
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<androidx.fragment.app.FragmentContainerView
android:id="@+id/fragmentContainerView"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:defaultNavHost="true"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:navGraph="@navigation/nav_graph" />
</androidx.constraintlayout.widget.ConstraintLayout>Replace the content of nav_graph.xml with the code below.
<?xml version="1.0" encoding="utf-8"?>
<navigation xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/nav_graph"
app:startDestination="@id/blankFragment1">
<fragment
android:id="@+id/blankFragment1"
android:name="com.codelab.daniwebandroidtypesafenav.BlankFragment1"
android:label="fragment_blank1"
tools:layout="@layout/fragment_blank1" >
<action
android:id="@+id/action_blankFragment1_to_blankFragment2"
app:destination="@id/blankFragment2" />
</fragment>
<fragment
android:id="@+id/blankFragment2"
android:name="com.codelab.daniwebandroidtypesafenav.BlankFragment2"
android:label="fragment_blank2"
tools:layout="@layout/fragment_blank2" />
</navigation>Add the string resource below into strings.xml.
<string name="second_screen">2nd Screen</string>Replace the content of fragment_blank1.xml with the code below.
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/frameLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".BlankFragment1" >
<Button
android:id="@+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/second_screen"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>Before diving into navigation type safety, we will first look at what navigation without type safety is like. Copy and paste the overridden version of onViewCreated() below into BlankFragment1.
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
val navController = findNavController()
val button = view.findViewById<Button>(R.id.button)
button.setOnClickListener {
//Will compile, but will crash at runtime. No Compiler checks (except for @IdRes).
navController.navigate(R.id.button)
//Will compile. Won't crash at runtime. No Compiler checks (except for @IdRes).
//navController.navigate(R.id.action_blankFragment1_to_blankFragment2)
//Will compile. Won't crash at runtime. Has Compiler checks
//val direction = BlankFragment1Directions.actionBlankFragment1ToBlankFragment2()
//navController.navigate(direction)
}
}The code snippet above presents three different ways to navigate to a destination using a NavController. Without type safety, we normally can navigate using the android:id of the navigation <action>. When dissecting the method signature of the NavController#navigate(),
public open fun navigate(@IdRes resId: Int)then we can see that it will take just about any Int argument. We can pass a useful Int value from R.id, or any number, really. There is an annotation @IdRes applied to the parameter which helps a bit due to the IDEs annotation processor. If you were to provide a non-id number to navigate(), you will see some help from the IDE in the form of a compiler error, which can be suppressed.
Right now, we are passing to navigate() a valid R.id.button,
navController.navigate(R.id.button)but it is not a valid navigation <action>, so we will not see any compiler error. The code will compile, but it will crash at runtime when we press the Button.
java.lang.IllegalArgumentException: Navigation action/destination com.codelab.daniwebandroidtypesafenav:id/button cannot be found from the current destination 
The second way to navigate using the <action> android:id is correct and will not crash, but it is still not typesafe.
navController.navigate(R.id.action_blankFragment1_to_blankFragment2)Because we have added the safe-args dependencies into our project, we can now use navigation with type safety. Type safety is provided by the interface NavDirections. The safe-args dependencies will generate a class implementing NavDirections at development time for each originating Destination of an <action>. This class will have the same name as the originating fragment, but with the word Directions suffixed to it. This new class will also have methods with the same name as the <action> android:id, converted to camel case after stripping out underscores (_).
You can now comment out the first two ways to navigate and uncomment the last way to navigate with NavDirections.
In this section, we will learn how to pass arguments with Safe Args.
Replace the content of fragment_blank2.xml with the code below.
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/frameLayout2"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".BlankFragment2">
<TextView
android:id="@+id/textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="32sp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
tools:text="Test Test Test" />
</androidx.constraintlayout.widget.ConstraintLayout>To pass an argument to blankFragment2 when navigating to it from blankFragment1, we will have to do a couple of things.
We have to add an <argument> element to the destination fragment (blankFragment2). This will trigger the compiler to add a parameter to the method actionBlankFragment1ToBlankFragment2(), so it will become actionBlankFragment1ToBlankFragment2(sampleArgs: String = default value) (if <argument> has the attribute android:defaultValue). In nav_graph.xml, inside of blankFragment2, add the <argument> below.
<argument
android:name="sampleArg"
app:argType="string"
android:defaultValue="blank" />You might have to rebuild the project for the compiler to generate the new class.
Back in the Buttons onClickListener callback, we can replace the previous direction with the code below to pass an argument.
val direction = BlankFragment1Directions.actionBlankFragment1ToBlankFragment2("Arg from fragment1 to fragment2")In order for BlankFragment2 to receive the arguments, we can use the navArgs() delegate from androidx.navigation.fragment to receive a type of BlankFragment2Args, which the compiler has generated for us as well. In BlankFragment2.kt, copy and paste the code below.
val args: BlankFragment2Args by navArgs()
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
val textView = view.findViewById<TextView>(R.id.textView)
textView.text = args.sampleArg
}And that is the last step in this tutorial.
We are not ready to run the App. Your app should behave similarly to the Gif below.
BlankFragment1.kt
package com.codelab.daniwebandroidtypesafenav
import android.os.Bundle
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.Button
import androidx.navigation.fragment.findNavController
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private const val ARG_PARAM1 = "param1"
private const val ARG_PARAM2 = "param2"
/**
* A simple [Fragment] subclass.
* Use the [BlankFragment1.newInstance] factory method to
* create an instance of this fragment.
*/
class BlankFragment1 : Fragment() {
// TODO: Rename and change types of parameters
private var param1: String? = null
private var param2: String? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
arguments?.let {
param1 = it.getString(ARG_PARAM1)
param2 = it.getString(ARG_PARAM2)
}
}
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_blank1, container, false)
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
val navController = findNavController()
val button = view.findViewById<Button>(R.id.button)
button.setOnClickListener {
//Will compile, but will crash at runtime. No Compiler checks (except for @IdRes).
//navController.navigate(R.id.button)
//Will compile. Won't crash at runtime. No Compiler checks (except for @IdRes).
//navController.navigate(R.id.action_blankFragment1_to_blankFragment2)
//Will compile. Won't crash at runtime. Has Compiler checks
//val direction = BlankFragment1Directions.actionBlankFragment1ToBlankFragment2()
val direction = BlankFragment1Directions.actionBlankFragment1ToBlankFragment2("Arg from fragment1 to fragment2")
navController.navigate(direction)
}
}
companion object {
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* @param param1 Parameter 1.
* @param param2 Parameter 2.
* @return A new instance of fragment BlankFragment1.
*/
// TODO: Rename and change types and number of parameters
@JvmStatic
fun newInstance(param1: String, param2: String) =
BlankFragment1().apply {
arguments = Bundle().apply {
putString(ARG_PARAM1, param1)
putString(ARG_PARAM2, param2)
}
}
}
}BlankFragment2.kt
package com.codelab.daniwebandroidtypesafenav
import android.os.Bundle
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import androidx.navigation.fragment.navArgs
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private const val ARG_PARAM1 = "param1"
private const val ARG_PARAM2 = "param2"
/**
* A simple [Fragment] subclass.
* Use the [BlankFragment2.newInstance] factory method to
* create an instance of this fragment.
*/
class BlankFragment2 : Fragment() {
// TODO: Rename and change types of parameters
private var param1: String? = null
private var param2: String? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
arguments?.let {
param1 = it.getString(ARG_PARAM1)
param2 = it.getString(ARG_PARAM2)
}
}
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_blank2, container, false)
}
val args: BlankFragment2Args by navArgs()
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
val textView = view.findViewById<TextView>(R.id.textView)
textView.text = args.sampleArg
}
companion object {
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* @param param1 Parameter 1.
* @param param2 Parameter 2.
* @return A new instance of fragment BlankFragment2.
*/
// TODO: Rename and change types and number of parameters
@JvmStatic
fun newInstance(param1: String, param2: String) =
BlankFragment2().apply {
arguments = Bundle().apply {
putString(ARG_PARAM1, param1)
putString(ARG_PARAM2, param2)
}
}
}
}activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<androidx.fragment.app.FragmentContainerView
android:id="@+id/fragmentContainerView"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:defaultNavHost="true"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:navGraph="@navigation/nav_graph" />
</androidx.constraintlayout.widget.ConstraintLayout>fragment_blank1.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/frameLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".BlankFragment1" >
<Button
android:id="@+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/second_screen"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>fragment_blank2.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/frameLayout2"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".BlankFragment2">
<TextView
android:id="@+id/textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="32sp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
tools:text="Test Test Test" />
</androidx.constraintlayout.widget.ConstraintLayout>nav_graph.xml
<?xml version="1.0" encoding="utf-8"?>
<navigation xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/nav_graph"
app:startDestination="@id/blankFragment1">
<fragment
android:id="@+id/blankFragment1"
android:name="com.codelab.daniwebandroidtypesafenav.BlankFragment1"
android:label="fragment_blank1"
tools:layout="@layout/fragment_blank1" >
<action
android:id="@+id/action_blankFragment1_to_blankFragment2"
app:destination="@id/blankFragment2" />
</fragment>
<fragment
android:id="@+id/blankFragment2"
android:name="com.codelab.daniwebandroidtypesafenav.BlankFragment2"
android:label="fragment_blank2"
tools:layout="@layout/fragment_blank2" >
<argument
android:name="sampleArg"
app:argType="string"
android:defaultValue="blank" />
</fragment>
</navigation>strings.xml
<resources>
<string name="app_name">Daniweb Android Typesafe Nav</string>
<!-- TODO: Remove or change this placeholder text -->
<string name="hello_blank_fragment">Hello blank fragment</string>
<string name="second_screen">2nd Screen</string>
</resources>Project build.gradle
// Top-level build file where you can add configuration options common to all sub-projects/modules.
buildscript {
repositories {
google()
}
dependencies {
def nav_version = "2.4.0"
classpath "androidx.navigation:navigation-safe-args-gradle-plugin:$nav_version"
}
}
plugins {
id 'com.android.application' version '7.0.4' apply false
id 'com.android.library' version '7.0.4' apply false
id 'org.jetbrains.kotlin.android' version '1.6.10' apply false
}
task clean(type: Delete) {
delete rootProject.buildDir
}Module build.gradle
plugins {
id 'com.android.application'
id 'org.jetbrains.kotlin.android'
id 'androidx.navigation.safeargs.kotlin'
}
android {
compileSdk 31
defaultConfig {
applicationId "com.codelab.daniwebandroidtypesafenav"
minSdk 21
targetSdk 31
versionCode 1
versionName "1.0"
testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
}
}
compileOptions {
sourceCompatibility JavaVersion.VERSION_1_8
targetCompatibility JavaVersion.VERSION_1_8
}
kotlinOptions {
jvmTarget = '1.8'
}
}
dependencies {
implementation 'androidx.legacy:legacy-support-v4:1.0.0'
def nav_version = "2.4.0"
implementation "androidx.navigation:navigation-fragment-ktx:$nav_version"
implementation "androidx.navigation:navigation-ui-ktx:$nav_version"
implementation 'androidx.core:core-ktx:1.7.0'
implementation 'androidx.appcompat:appcompat:1.4.1'
implementation 'com.google.android.material:material:1.5.0'
implementation 'androidx.constraintlayout:constraintlayout:2.1.3'
testImplementation 'junit:junit:4.13.2'
androidTestImplementation 'androidx.test.ext:junit:1.1.3'
androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
}We have learned how to navigate with type safety and pass destination arguments in this tutorial. The full project code can be found at https://github.com/dmitrilc/DaniwebAndroidTypesafeNav.
If you are working on a native Android app using the View system, then you might have come across a situation where you would need to add a Composable (androidx.compose.runtime.Composable) into your View hierarchy. In this tutorial, we will learn how to add a Composable into an existing View system.
The Composables that we will use in this tutorial will come from the Material 3 library.
At the end of the tutorial, you would have learned:
To follow along with the tutorial, perform the steps below:
Create a new Android project with the default Empty Activity.
Remove the default Hello World! TextView from activity_main.xml.
Inside of your module build.gradle, upgrade your modules Material dependency to version 1.5.0.
implementation 'com.google.android.material:material:1.5.0'Add the variable below to hold the compose version.
def composeVersion = '1.0.5'Add these options to your android build options (the android{} block)
buildFeatures {
compose true
}
composeOptions {
kotlinCompilerExtensionVersion = composeVersion
}Add the Compose dependencies below into your dependencies{} block.
//Compose
implementation "androidx.compose.runtime:runtime:$composeVersion"
implementation "androidx.compose.ui:ui:$composeVersion"
implementation "androidx.compose.ui:ui-tooling:$composeVersion"
implementation "androidx.compose.foundation:foundation:$composeVersion"
implementation "androidx.compose.foundation:foundation-layout:$composeVersion"Add Compose support for Material 3.
//Material 3 Compose Support
implementation 'androidx.compose.material3:material3:1.0.0-alpha04'For simplicity, in the project build.gradle file, downgrade your Android Kotlin plugin version to 1.5.31.
id 'org.jetbrains.kotlin.android' version '1.5.31' apply falseTo bridge the gap between the Compose world and the View world, Android provides a couple of Interop APIs. ComposeView (androidx.compose.ui.platform.ComposeView) is one of those APIs that we can use in scenarios where we need to insert a Composable into an existing View hierarchy.
ComposeView is actually a View itself, so we will be able to add it via XML. To add it to activity_main.xml, copy and paste the code below inside of ConstraintLayout.
<androidx.compose.ui.platform.ComposeView
android:id="@+id/compose_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />For this tutorial, we can just add a simple Composable that will print the String "Hello" 100 times.
In MainActivity.kt, add the top-level Composable below.
@Composable
private fun Hellos(hellos: Array<String> = Array(100) {"Hello $it"} ) {
LazyColumn {
items(items = hellos) { hello ->
Text(text = hello)
}
}
}Next, we will obtain the reference to the <ComposeView>. Inside of onCreate(), after the setContent() call, add the line of code below.
val composeView = findViewById<ComposeView>(R.id.compose_view)To make use of composeView, we have two options: call setContent() directly from the composeView variable or use the Kotlin scope function apply(). We will be using apply() in this case because it has the advantage of calling multiple functions on composeView rather than just a singular setContent(). Append the code snippet below into onCreate().
composeView.apply {
setContent {
Hellos()
}
}We are almost done, but there is another important characteristic of ComposeView that needs discussion.
ComposeView also subclasses AbstractComposeView(androidx.compose.ui.platform.AbstractComposeView). AbstractComposeView includes an interesting function that is setViewCompositionStrategy(). Because we are mixing two different UI systems together, we will need to be aware of the Activity (or Fragment), View, and Composable lifecycles. With setViewCompositionStrategy(), we can pass in a ViewCompositionStrategy object to configure how the composition should be destroyed. There are three premade ViewCompositionStrategy available for us to use.
DisposeOnViewTreeLifecycleDestroyed, but this is a class with constructors that allows you to specify a specific lifecycle.To set the ViewCompositionStrategy, you can add it to the apply() like below.
composeView.apply {
//Default option
//setViewCompositionStrategy(ViewCompositionStrategy.DisposeOnViewTreeLifecycleDestroyed)
//Explicit lifeCycle
//setViewCompositionStrategy(ViewCompositionStrategy.DisposeOnLifecycleDestroyed(lifecycle))
setViewCompositionStrategy(ViewCompositionStrategy.DisposeOnViewTreeLifecycleDestroyed)
setContent {
Hellos()
}
}It is now time to run our App to see if it works correctly.
We can see that it displays the Composable LazyList inside of our ConstraintLayout View successfully.
MainActivity.kt
package com.codelab.daniwebcomposeinviews
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.compose.foundation.lazy.LazyColumn
import androidx.compose.foundation.lazy.items
import androidx.compose.material3.Text
import androidx.compose.runtime.Composable
import androidx.compose.ui.platform.ComposeView
import androidx.compose.ui.platform.ViewCompositionStrategy
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val composeView = findViewById<ComposeView>(R.id.compose_view)
/* composeView.setContent {
Hellos()
}*/
composeView.apply {
//Default option
//setViewCompositionStrategy(ViewCompositionStrategy.DisposeOnViewTreeLifecycleDestroyed)
//Explicit lifeCycle
//setViewCompositionStrategy(ViewCompositionStrategy.DisposeOnLifecycleDestroyed(lifecycle))
setViewCompositionStrategy(ViewCompositionStrategy.DisposeOnViewTreeLifecycleDestroyed)
setContent {
Hellos()
}
}
}
}
@Composable
private fun Hellos(hellos: Array<String> = Array(100) {"Hello $it"} ) {
LazyColumn {
items(items = hellos) { hello ->
Text(text = hello)
}
}
}activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<androidx.compose.ui.platform.ComposeView
android:id="@+id/compose_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>Project build.gradle
// Top-level build file where you can add configuration options common to all sub-projects/modules.
plugins {
id 'com.android.application' version '7.1.0' apply false
id 'com.android.library' version '7.1.0' apply false
id 'org.jetbrains.kotlin.android' version '1.5.31' apply false
}
task clean(type: Delete) {
delete rootProject.buildDir
}Module build.gradle
plugins {
id 'com.android.application'
id 'org.jetbrains.kotlin.android'
}
def composeVersion = '1.0.5'
android {
compileSdk 31
defaultConfig {
applicationId "com.codelab.daniwebcomposeinviews"
minSdk 21
targetSdk 31
versionCode 1
versionName "1.0"
testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
}
}
compileOptions {
sourceCompatibility JavaVersion.VERSION_1_8
targetCompatibility JavaVersion.VERSION_1_8
}
kotlinOptions {
jvmTarget = '1.8'
}
buildFeatures {
compose true
}
composeOptions {
kotlinCompilerExtensionVersion = composeVersion
}
}
dependencies {
//Compose
implementation "androidx.compose.runtime:runtime:$composeVersion"
implementation "androidx.compose.ui:ui:$composeVersion"
implementation "androidx.compose.ui:ui-tooling:$composeVersion"
implementation "androidx.compose.foundation:foundation:$composeVersion"
implementation "androidx.compose.foundation:foundation-layout:$composeVersion"
//Material 3 Compose Support
implementation 'androidx.compose.material3:material3:1.0.0-alpha04'
implementation 'com.google.android.material:material:1.5.0'
implementation 'androidx.core:core-ktx:1.7.0'
implementation 'androidx.appcompat:appcompat:1.4.1'
implementation 'androidx.constraintlayout:constraintlayout:2.1.3'
testImplementation 'junit:junit:4.13.2'
androidTestImplementation 'androidx.test.ext:junit:1.1.3'
androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
}We have learned how to add Composables into a View hierarchy using ComposeView. The full project code can be found at https://github.com/dmitrilc/DaniwebComposeInViews.
android ,android development,UI
Hello everyone, I'm just starting to dig into the android apps development and would like to find really useful courses. Help me choose the best ones, please!
Hello i want to retrieve multiples values from single column on db. And i did. They are shown on Console (Painting, Illustration, Graphic Design) but when i put the values on ion-toggles with ngModel only one is set to true. As you may see on the screenshot the values are returning but only Painting is true (toggle on right side)
Html
<ion-list >
<ion-list-header>
I am Interested in...
</ion-list-header><div><br /></div>
<ion-item>
<ion-label>Painting</ion-label>
<ion-toggle color="gold" [ngModel]="interest=='Painting' ? true:false" (ionChange)="creativeInterest(creative, 'Painting')"></ion-toggle>
</ion-item>
<ion-item>
<ion-label>Graphic Design</ion-label>
<ion-toggle color="tertiary" [ngModel]="interest=='Graphic Design' ? true:false" (ionChange)="creativeInterest(creative, 'Graphic Design')"></ion-toggle>
</ion-item>
<ion-item>
<ion-label>Illustration</ion-label>
<ion-toggle color="danger" [ngModel]="interest=='Illustration' ? true:false" (ionChange)="creativeInterest(creative, 'Illustration')"></ion-toggle>
</ion-item>
<ion-item>
<ion-label>Sculpture</ion-label>
<ion-toggle color="success" [ngModel]="interest=='Sculpture' ? true:false" (ionChange)="creativeInterest(creative, 'Sculpture')"></ion-toggle>
</ion-item>
<ion-item>
<ion-label>Literature</ion-label>
<ion-toggle color="danger" [ngModel]="interest=='Literature' ? true:false" (ionChange)="creativeInterest(creative, 'Literature')"></ion-toggle>
</ion-item>
<ion-item>
<ion-label>Theater</ion-label>
<ion-toggle color="dark" [ngModel]="interest=='Theater' ? true:false" (ionChange)="creativeInterest(creative, 'Theater')"></ion-toggle>
</ion-item>
<ion-item>
<ion-label>Film</ion-label>
<ion-toggle color="warning" [ngModel]="interest=='Film' ? true:false" (ionChange)="creativeInterest(creative, 'Film')"></ion-toggle>
</ion-item>.ts
export class CreativeSettingsPage implements OnInit {
creativeInterests: any=[];
creative: any= {};
userDetails: any = {};
interest:any=[];
constructor(
public userData: UserData
) {
this.userDetails = this.userData.getUserData();
}
ngOnInit() {
this.creativeInsterestSet();
}
creativeInsterestSet() {
this.userData.creativeInterests(this.userDetails.uid).pipe(
map((data: any) => {
if (data.success) {
this.creativeInterests = data.creativeInterests;
this.creativeInterests.filter(item => {
this.interest=item.interest;
console.log( this.interest);
});
}
})
).subscribe()
}If you are working with the latest Material 3 libraries on Android, you might have wondered how to use the Bottom Navigation Bar in your App. In this tutorial, we will learn how to use the Material 3 Bottom Navigation Bar (BNB).
At the end of the tutorial, you would have learned:
To follow along with the tutorial, perform the steps below:
Create a new Android project with the default Empty Activity.
Add the Material 3 dependency below into your projects build.gradle file.
implementation 'com.google.android.material:material:1.5.0'Sync Gradle.
Change the current theme(themes.xml) parent to Theme.Material3.DayNight.NoActionBar.
First, let us add the BNB into our project. I normally use BNB with a LinearLayout-based parent, but that is not a hard requirement. We can just add a BNB to the ConstraintLayout that we already have in activity_main.xml just fine.
Open activity_main.xml in Code view, add the code below under the default <TextView>. The code below already includes constraints for the parent ConstraintLayout, so you do not have to worry about them.
<com.google.android.material.bottomnavigation.BottomNavigationView
android:id="@+id/bottom_navigation"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:menu="@menu/bottom_navigation_menu" />Upon seeing the compile error Cannot resolve symbol '@menu/bottom_navigation_menu', go ahead and create the missing file with the same configurations as the screenshot below.
Because the newly created menu resource is empty, the BNB is just an empty bar. Let us assume that we are building an App for a taxi company, so we will add five shortcuts for the most frequently used features into the BNB. The five shortcuts are:
To add the five shortcuts to our BNB, follow the steps below:
Add these 5 vector assets from the built-in Clip Art library into res/drawable.
ic_baseline_local_taxi_24
ic_baseline_map_24
ic_baseline_emergency_24
ic_baseline_edit_calendar_24
ic_baseline_payment_24Add these 5 string resources into strings.xml.
<string name="text_label_1">Call Cab</string>
<string name="text_label_2">Map</string>
<string name="text_label_3">SOS</string>
<string name="text_label_4">Schedule</string>
<string name="text_label_5">Payment</string>Open the file bottom_navigation_menu.xml. Add these <item> elements as children of the root <menu>.
<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
<item
android:id="@+id/page_1"
android:enabled="true"
android:icon="@drawable/ic_baseline_local_taxi_24"
android:title="@string/text_label_1"/>
<item
android:id="@+id/page_2"
android:enabled="true"
android:icon="@drawable/ic_baseline_map_24"
android:title="@string/text_label_2"/>
<item
android:id="@+id/page_3"
android:enabled="true"
android:icon="@drawable/ic_baseline_emergency_24"
android:title="@string/text_label_3"/>
<item
android:id="@+id/page_4"
android:enabled="true"
android:icon="@drawable/ic_baseline_edit_calendar_24"
android:title="@string/text_label_4"/>
<item
android:id="@+id/page_5"
android:enabled="true"
android:icon="@drawable/ic_baseline_payment_24"
android:title="@string/text_label_5"/>
</menu>If you run the app now, you can see something similar to the animation below.
Currently, the BNB buttons are technically only dummy placeholders without any useful behavior. To bind user navigation actions to callbacks, you can use the function NavigationBarView#setOnItemSelectedLisenter(). Append the code below into MainActivity.kts onCreate().
val textView = findViewById<TextView>(R.id.textView)
val bottomNav = findViewById<BottomNavigationView>(R.id.bottom_navigation)
bottomNav.setOnItemSelectedListener { item ->
when(item.itemId){
R.id.page_1 -> {
textView.text = getString(R.string.text_label_1)
true
}
R.id.page_2 -> {
textView.text = getString(R.string.text_label_2)
true
}
R.id.page_3 -> {
textView.text = getString(R.string.text_label_3)
true
}
R.id.page_4 -> {
textView.text = getString(R.string.text_label_4)
true
}
R.id.page_5 -> {
textView.text = getString(R.string.text_label_5)
true
}
else -> false
}
}Now the default TextView will change every time a navigation action occurs. Run the app again and it will behave similarly to the animation below.
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<TextView
android:id="@+id/textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Hello World!"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<com.google.android.material.bottomnavigation.BottomNavigationView
android:id="@+id/bottom_navigation"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:menu="@menu/bottom_navigation_menu" />
</androidx.constraintlayout.widget.ConstraintLayout>MainActivity.kt
package com.example.daniwebmaterial3bottomnavigationbar
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.TextView
import com.google.android.material.bottomnavigation.BottomNavigationView
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val textView = findViewById<TextView>(R.id.textView)
val bottomNav = findViewById<BottomNavigationView>(R.id.bottom_navigation)
bottomNav.setOnItemSelectedListener { item ->
when(item.itemId){
R.id.page_1 -> {
textView.text = getString(R.string.text_label_1)
true
}
R.id.page_2 -> {
textView.text = getString(R.string.text_label_2)
true
}
R.id.page_3 -> {
textView.text = getString(R.string.text_label_3)
true
}
R.id.page_4 -> {
textView.text = getString(R.string.text_label_4)
true
}
R.id.page_5 -> {
textView.text = getString(R.string.text_label_5)
true
}
else -> false
}
}
}
}bottom_navigation_menu.xml
<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
<item
android:id="@+id/page_1"
android:enabled="true"
android:icon="@drawable/ic_baseline_local_taxi_24"
android:title="@string/text_label_1"/>
<item
android:id="@+id/page_2"
android:enabled="true"
android:icon="@drawable/ic_baseline_map_24"
android:title="@string/text_label_2"/>
<item
android:id="@+id/page_3"
android:enabled="true"
android:icon="@drawable/ic_baseline_emergency_24"
android:title="@string/text_label_3"/>
<item
android:id="@+id/page_4"
android:enabled="true"
android:icon="@drawable/ic_baseline_edit_calendar_24"
android:title="@string/text_label_4"/>
<item
android:id="@+id/page_5"
android:enabled="true"
android:icon="@drawable/ic_baseline_payment_24"
android:title="@string/text_label_5"/>
</menu>strings.xml
<resources>
<string name="app_name">Daniweb Material 3 Bottom Navigation Bar</string>
<string name="text_label_1">Call Cab</string>
<string name="text_label_2">Map</string>
<string name="text_label_3">SOS</string>
<string name="text_label_4">Schedule</string>
<string name="text_label_5">Payment</string>
</resources>themes.xml
<resources xmlns:tools="http://schemas.android.com/tools">
<!-- Base application theme. -->
<style name="Theme.DaniwebMaterial3BottomNavigationBar" parent="Theme.Material3.DayNight.NoActionBar">
<!-- Primary brand color. -->
<item name="colorPrimary">@color/purple_500</item>
<item name="colorPrimaryVariant">@color/purple_700</item>
<item name="colorOnPrimary">@color/white</item>
<!-- Secondary brand color. -->
<item name="colorSecondary">@color/teal_200</item>
<item name="colorSecondaryVariant">@color/teal_700</item>
<item name="colorOnSecondary">@color/black</item>
<!-- Status bar color. -->
<item name="android:statusBarColor" tools:targetApi="l">?attr/colorPrimaryVariant</item>
<!-- Customize your theme here. -->
</style>
</resources>build.gradle
plugins {
id 'com.android.application'
id 'kotlin-android'
}
android {
compileSdk 31
defaultConfig {
applicationId "com.example.daniwebmaterial3bottomnavigationbar"
minSdk 21
targetSdk 31
versionCode 1
versionName "1.0"
testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
}
}
compileOptions {
sourceCompatibility JavaVersion.VERSION_1_8
targetCompatibility JavaVersion.VERSION_1_8
}
kotlinOptions {
jvmTarget = '1.8'
}
}
dependencies {
implementation 'com.google.android.material:material:1.5.0'
implementation 'androidx.core:core-ktx:1.7.0'
implementation 'androidx.appcompat:appcompat:1.4.1'
implementation 'com.google.android.material:material:1.5.0'
implementation 'androidx.constraintlayout:constraintlayout:2.1.3'
testImplementation 'junit:junit:4.+'
androidTestImplementation 'androidx.test.ext:junit:1.1.3'
androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
}We have learned how to use the Bottom Navigation Bar. The full project code can be found at https://github.com/dmitrilc/DaniwebMaterial3BottomNavigationBar
Proto DataStore is a great way to store the permanent state of your application, especially if you prefer type safety. In this tutorial, we will learn how to store our App state using the Proto DataStore.
At the end of the tutorial, you would have learned:
To follow along with the tutorial, perform the steps below:
Create a new Android project with the default Empty Activity.
Remove the default Hello World! TextView.
Add the Gradle dependency below into your project build.gradle.
implementation "androidx.lifecycle:lifecycle-runtime-ktx:2.4.0"
implementation "androidx.datastore:datastore:1.0.0"
implementation com.google.protobuf:protobuf-javalite:3.19.3Add the Google protobuf plugin to your project build.gradle.
id "com.google.protobuf" version "0.8.18"Append the configuration below to the end of your project build.gradle.
protobuf {
protoc {
artifact = 'com.google.protobuf:protoc:3.8.0'
}
generateProtoTasks {
all().each { task ->
task.builtins {
java {
option "lite"
}
}
}
}
}If you are not sure what these steps do, the instructions for setting up protobuf in your Android project can also be found in the official docs here.
Add the code below inside of <ConstraintLayout>. This will add four checkboxes.
<CheckBox
android:id="@+id/checkBox1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/checkbox1"
app:layout_constraintBottom_toTopOf="@+id/checkBox2"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<CheckBox
android:id="@+id/checkBox2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/checkbox2"
app:layout_constraintBottom_toTopOf="@+id/checkBox3"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/checkBox1" />
<CheckBox
android:id="@+id/checkBox3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/checkbox3"
app:layout_constraintBottom_toTopOf="@+id/checkBox4"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/checkBox2" />
<CheckBox
android:id="@+id/checkBox4"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/checkbox4"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/checkBox3" />Add the string resources below into strings.xml.
<string name="checkbox1">CheckBox 1</string>
<string name="checkbox2">CheckBox 2</string>
<string name="checkbox3">CheckBox 3</string>
<string name="checkbox4">CheckBox 4</string>Our sample app for this tutorial is quite simple. It has one activity and four checkboxes.
Currently, the app is unable to remember which checkbox is checked after the app is killed. For the app to be able to save its state after it has been killed, we can employ the help of the Proto DataStore.
The Proto DataStore is not the only way to persist app states, but is merely one of the many methods to achieve this goal.
Similar to how you would define JPA Entities, Proto DataStore requires a schema file declared using the protobuf language. We are using latest version of protobuf (protobuf3) for this tutorial.
Follow the steps below to create a schema for our App.
Under the Project panel of Android Studio, switches from Android to Project view.
Navigate to app/src/main.
Right-click on main > New > Directory, name the new directory proto.
Right-click on the newly created directory proto > New > File, name the new file CheckBoxStates.proto. You might need to install the official Protocol Buffers (from Jetbrains) plugin for Android Studio here for the protobuf3 syntax highlighting to show.
Paste the code below into CheckboxStates.proto.
syntax = "proto3";
option java_package = "com.example.daniwebprotobufdatastore";
option java_multiple_files = true;
message CheckboxStates {
bool check_box_1 = 1;
bool check_box_2 = 2;
bool check_box_3 = 3;
bool check_box_4 = 4;
}Rebuild your project.
Now that we have our schema, the next step is to create a class that can serialize the protobuf data into POJOs and vice-versa.
Create a new class called CheckboxStatesSerializer.kt in the same package as MainActivity.kt.
Copy and paste the code below into it. This is the class that serialize/de-serialize your CheckboxStates POJO as well as providing a default instance of CheckboxStates.
package com.example.daniwebprotobufdatastore
import android.content.Context
import androidx.datastore.core.CorruptionException
import androidx.datastore.core.DataStore
import androidx.datastore.core.Serializer
import androidx.datastore.dataStore
import com.google.protobuf.InvalidProtocolBufferException
import java.io.InputStream
import java.io.OutputStream
object CheckboxStatesSerializer: Serializer<CheckboxStates> {
override val defaultValue: CheckboxStates
get() = CheckboxStates.getDefaultInstance()
override suspend fun readFrom(input: InputStream): CheckboxStates {
try {
return CheckboxStates.parseFrom(input)
} catch (exception: InvalidProtocolBufferException) {
throw CorruptionException("Cannot read proto.", exception)
}
}
override suspend fun writeTo(t: CheckboxStates, output: OutputStream) {
t.writeTo(output)
}
}
val Context.checkboxStatesDataStore: DataStore<CheckboxStates> by dataStore(
fileName = "checkbox_states.pb",
serializer = CheckboxStatesSerializer
)The checkboxStatesDataStore extension property with the Context receiver exposes an instance of DataStore for us to use.
Using the DataStore extension property of Context, we can read and write to the DataStore. Follow the steps below to save checkbox states.
In MainActivity.kt, add the saveCheckboxStates() function below.
private suspend fun saveCheckboxStates() {
val checkbox1 = findViewById<CheckBox>(R.id.checkBox1)
val checkbox2 = findViewById<CheckBox>(R.id.checkBox2)
val checkbox3 = findViewById<CheckBox>(R.id.checkBox3)
val checkbox4 = findViewById<CheckBox>(R.id.checkBox4)
applicationContext.checkboxStatesDataStore.updateData { states ->
states.toBuilder()
.setCheckBox1(checkbox1.isChecked)
.setCheckBox2(checkbox2.isChecked)
.setCheckBox3(checkbox3.isChecked)
.setCheckBox4(checkbox4.isChecked)
.build()
}
}Since IO writing is expensive, we will save the state only at the onStop() lifecycle callback for this tutorial. Override onStop(). To keep things simple, I am doing everything from the Activity here, but this job is more fit a ViewModel.
override fun onStop() {
super.onStop()
lifecycleScope.launch {
saveCheckboxStates()
}
}Next, we will add code to restore the state when the app is started again after being killed.
Add the restoreCheckboxStates() function below to MainActivity.
private suspend fun restoreCheckBoxStates() {
val checkbox1 = findViewById<CheckBox>(R.id.checkBox1)
val checkbox2 = findViewById<CheckBox>(R.id.checkBox2)
val checkbox3 = findViewById<CheckBox>(R.id.checkBox3)
val checkbox4 = findViewById<CheckBox>(R.id.checkBox4)
applicationContext.checkboxStatesDataStore.data.collect { states ->
checkbox1.isChecked = states.checkBox1
checkbox2.isChecked = states.checkBox2
checkbox3.isChecked = states.checkBox3
checkbox4.isChecked = states.checkBox4
}
}Append the code below to onCreate() to restore the state. Again, you should properly do this in a ViewModel instead.
lifecycleScope.launch {
restoreCheckBoxStates()
}We are now ready to run the App. Your app should properly save the state when performing a workflow similar to the animation below.
CheckboxStatesSerializer.kt
package com.example.daniwebprotobufdatastore
import android.content.Context
import androidx.datastore.core.CorruptionException
import androidx.datastore.core.DataStore
import androidx.datastore.core.Serializer
import androidx.datastore.dataStore
import com.google.protobuf.InvalidProtocolBufferException
import java.io.InputStream
import java.io.OutputStream
object CheckboxStatesSerializer: Serializer<CheckboxStates> {
override val defaultValue: CheckboxStates
get() = CheckboxStates.getDefaultInstance()
override suspend fun readFrom(input: InputStream): CheckboxStates {
try {
return CheckboxStates.parseFrom(input)
} catch (exception: InvalidProtocolBufferException) {
throw CorruptionException("Cannot read proto.", exception)
}
}
override suspend fun writeTo(t: CheckboxStates, output: OutputStream) {
t.writeTo(output)
}
}
val Context.checkboxStatesDataStore: DataStore<CheckboxStates> by dataStore(
fileName = "checkbox_states.pb",
serializer = CheckboxStatesSerializer
)MainActivity.kt
package com.example.daniwebprotobufdatastore
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.CheckBox
import androidx.lifecycle.coroutineScope
import androidx.lifecycle.lifecycleScope
import kotlinx.coroutines.flow.collect
import kotlinx.coroutines.launch
import kotlinx.coroutines.runBlocking
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
lifecycleScope.launch {
restoreCheckBoxStates()
}
}
private suspend fun restoreCheckBoxStates() {
val checkbox1 = findViewById<CheckBox>(R.id.checkBox1)
val checkbox2 = findViewById<CheckBox>(R.id.checkBox2)
val checkbox3 = findViewById<CheckBox>(R.id.checkBox3)
val checkbox4 = findViewById<CheckBox>(R.id.checkBox4)
applicationContext.checkboxStatesDataStore.data.collect { states ->
checkbox1.isChecked = states.checkBox1
checkbox2.isChecked = states.checkBox2
checkbox3.isChecked = states.checkBox3
checkbox4.isChecked = states.checkBox4
}
}
private suspend fun saveCheckboxStates() {
val checkbox1 = findViewById<CheckBox>(R.id.checkBox1)
val checkbox2 = findViewById<CheckBox>(R.id.checkBox2)
val checkbox3 = findViewById<CheckBox>(R.id.checkBox3)
val checkbox4 = findViewById<CheckBox>(R.id.checkBox4)
applicationContext.checkboxStatesDataStore.updateData { states ->
states.toBuilder()
.setCheckBox1(checkbox1.isChecked)
.setCheckBox2(checkbox2.isChecked)
.setCheckBox3(checkbox3.isChecked)
.setCheckBox4(checkbox4.isChecked)
.build()
}
}
override fun onStop() {
super.onStop()
lifecycleScope.launch {
saveCheckboxStates()
}
}
}strings.xml
<resources>
<string name="app_name">Daniweb protobuf DataStore</string>
<string name="checkbox1">CheckBox 1</string>
<string name="checkbox2">CheckBox 2</string>
<string name="checkbox3">CheckBox 3</string>
<string name="checkbox4">CheckBox 4</string>
</resources>build.gradle
plugins {
id 'com.android.application'
id 'kotlin-android'
id "com.google.protobuf" version "0.8.18"
}
android {
compileSdk 31
defaultConfig {
applicationId "com.example.daniwebprotobufdatastore"
minSdk 21
targetSdk 31
versionCode 1
versionName "1.0"
testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
}
}
compileOptions {
sourceCompatibility JavaVersion.VERSION_1_8
targetCompatibility JavaVersion.VERSION_1_8
}
kotlinOptions {
jvmTarget = '1.8'
}
}
dependencies {
implementation "androidx.lifecycle:lifecycle-runtime-ktx:2.4.0"
implementation 'com.google.protobuf:protobuf-javalite:3.19.3'
implementation "androidx.datastore:datastore:1.0.0"
implementation 'androidx.core:core-ktx:1.7.0'
implementation 'androidx.appcompat:appcompat:1.4.1'
implementation 'com.google.android.material:material:1.5.0'
implementation 'androidx.constraintlayout:constraintlayout:2.1.3'
testImplementation 'junit:junit:4.+'
androidTestImplementation 'androidx.test.ext:junit:1.1.3'
androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
}
protobuf {
protoc {
artifact = 'com.google.protobuf:protoc:3.8.0'
}
generateProtoTasks {
all().each { task ->
task.builtins {
java {
option "lite"
}
}
}
}
}activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<CheckBox
android:id="@+id/checkBox1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/checkbox1"
app:layout_constraintBottom_toTopOf="@+id/checkBox2"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<CheckBox
android:id="@+id/checkBox2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/checkbox2"
app:layout_constraintBottom_toTopOf="@+id/checkBox3"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/checkBox1" />
<CheckBox
android:id="@+id/checkBox3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/checkbox3"
app:layout_constraintBottom_toTopOf="@+id/checkBox4"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/checkBox2" />
<CheckBox
android:id="@+id/checkBox4"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/checkbox4"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/checkBox3" />
</androidx.constraintlayout.widget.ConstraintLayout>We have learned how to persist state using Proto DataStore. The full project code can be found at https://github.com/dmitrilc/DaniwebProtobufDataStore