Category: Mobile Development

In this tutorial, we will learn how to filter and validate Intents fired from the application under test.

At the end of the tutorial, you would have learned:

1. How to filter and validate Intents in Espresso tests.

1. Android Studio. The version used in this tutorial is Android Studio Chipmunk 2021.2.1 Patch 1.

1. Intermediate Android.
2. Basic Espresso.

To follow along with the tutorial, perform the steps below:

1. Create a new Android project with the default Empty Activity.

2. Add the <string> resource below into strings.xml.

    <string name="launch_intent">Launch Intent</string>

3. Replace the code inside activity_main.xml with the code below. This simply adds a Button.

    <?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_launchIntent"
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:text="@string/launch_intent"
           app:layout_constraintBottom_toBottomOf="parent"
           app:layout_constraintEnd_toEndOf="parent"
           app:layout_constraintStart_toStartOf="parent"
           app:layout_constraintTop_toTopOf="parent" />
    </androidx.constraintlayout.widget.ConstraintLayout>

4. Add the dependencies below into your module build.gradle file.

    androidTestImplementation 'androidx.test:runner:1.4.0'
    androidTestImplementation 'androidx.test:rules:1.4.0'
    androidTestImplementation 'androidx.test.espresso:espresso-intents:3.4.0'

5. Remove all test cases from ExampleInstrumentedTest in your androidTest source set. Your ExampleInstrumentedTest file should look like the empty class below.

    @RunWith(AndroidJUnit4::class)
    class ExampleInstrumentedTest {
    }

6. Append MainActivity#onCreate() with the code below.

    findViewById<Button>(R.id.button_launchIntent).setOnClickListener {
       val intent = Intent(ACTION_VIEW).apply {
           data = intentData
       }
   
       startActivity(intent)
    }

7. Add the companion object below into MainActivity as well.

    companion object {
       val intentData: Uri = Uri.Builder()
           .scheme("geo")
           .query("0,0")
           .appendQueryParameter("q", "First St SE, Washington, DC, 20004")
           .build()
    }

The tutorial app is a super simple app with a single Button. After clicking on the Button, the app will attempt to launch an Activity that can consume the Uri scheme geo. There is only one app on my emulator that can do this, which is the default Google Maps app.

The Intent launched is an implicit Intent with data pointing to a specific location (US Capitol) on the world map. The data used for the Intent is shown below.

val intentData: Uri = Uri.Builder()
   .scheme("geo")
   .query("0,0")
   .appendQueryParameter("q", "First St SE, Washington, DC, 20004")
   .build()

Reference the animation below to get a feel of what the application does.

Copy and paste the code below into your ExampleInstrumentedTest class.

   @get:Rule
   val activityRule = ActivityScenarioRule(MainActivity::class.java)

/*    @Before
   fun startCapturingIntent(){
       Intents.init()
   }*/

/*    @After
   fun clearIntentsState() {
       Intents.release()
   }*/

   @Test
   fun intentTest(){
       onView(withId(R.id.button_launchIntent))
           .perform(click())

/*        Intents.intended(allOf(
           hasAction(ACTION_VIEW),
           hasData(MainActivity.intentData)
       ))*/
   }

The test intentTest() simply opens the app and then performs a click().

The test is still not aware of the Intent being fired yet, but the commented out sections of the code can help us capture and verify the Intent being fired.

For us to be able to capture Intents from the application under test, we can call Intents.init() before each test. Go ahead and uncomment startCapturingIntent().

@Before
fun startCapturingIntent(){
   Intents.init()
}

Because Intents#init() will modify an internal cache of Intents, it is very important that we must call Intents#release() after each test is completed to clear out this cache. Go ahead and uncomment the function clearIntentsState().

@After
fun clearIntentsState() {
   Intents.release()
}

The Intents class provides a couple of methods to access the captured Intents.

1. getIntents(): retrieve all captured Intents in a list.
2. intented() variants: find one or more Intents and perform verifications on them.
3. intending(): used for stubbing Intent responses.

In intentTest(), the method chosen was intended(). Go ahead and uncomment it out.

Intents.intended(allOf(
   hasAction(ACTION_VIEW),
   hasData(MainActivity.intentData)
))

To verify Intent information, we can use the convenient methods from the IntentMatchers class. hasAction() and hasData() do not exist on the vanilla Matchers class.

You can run the test now and verify whether it passes.

ExampleInstrumentedTest.kt

@RunWith(AndroidJUnit4::class)
class ExampleInstrumentedTest {

   @get:Rule
   val activityRule = ActivityScenarioRule(MainActivity::class.java)

   @Before
   fun startCapturingIntent(){
       Intents.init()
   }

   @After
   fun clearIntentsState() {
       Intents.release()
   }

   @Test
   fun intentTest(){
       onView(withId(R.id.button_launchIntent))
           .perform(click())

       Intents.intended(allOf(
           hasAction(ACTION_VIEW),
           hasData(MainActivity.intentData)
       ))
   }

}

MainActivity.kt

class MainActivity : AppCompatActivity() {
   override fun onCreate(savedInstanceState: Bundle?) {
       super.onCreate(savedInstanceState)
       setContentView(R.layout.activity_main)

       findViewById<Button>(R.id.button_launchIntent).setOnClickListener {
           val intent = Intent(ACTION_VIEW).apply {
               data = intentData
           }

           startActivity(intent)
       }
   }

   companion object {
       val intentData: Uri = Uri.Builder()
           .scheme("geo")
           .query("0,0")
           .appendQueryParameter("q", "First St SE, Washington, DC, 20004")
           .build()
   }
}

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_launchIntent"
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:text="@string/launch_intent"
       app:layout_constraintBottom_toBottomOf="parent"
       app:layout_constraintEnd_toEndOf="parent"
       app:layout_constraintStart_toStartOf="parent"
       app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

strings.xml

<resources>
   <string name="app_name">Daniweb Android Validate Intents</string>
   <string name="launch_intent">Launch Intent</string>
</resources>

Module build.gradle

plugins {
   id 'com.android.application'
   id 'org.jetbrains.kotlin.android'
}

android {
   compileSdk 32

   defaultConfig {
       applicationId "com.example.daniwebandroidvalidateintents"
       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:1.6.0'
   implementation 'androidx.constraintlayout:constraintlayout:2.1.4'
   testImplementation 'junit:junit:4.13.2'
   androidTestImplementation 'androidx.test.ext:junit:1.1.3'
   androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'

   androidTestImplementation 'androidx.test:runner:1.4.0'
   androidTestImplementation 'androidx.test:rules:1.4.0'
   androidTestImplementation 'androidx.test.espresso:espresso-intents:3.4.0'
}

We have learned how to test Intents in this tutorial. The full project code can be found at https://github.com/dmitrilc/DaniwebAndroidValidateIntents.

When working with Espresso tests, you might have found it hard to make Espresso wait for background tasks to complete before performing other actions or assertions. Fortunately, the classes in the Espresso idling package exist to cover this use case.

In this tutorial, we will learn how to use one of those classes called CountingIdlingResource.

At the end of the tutorial, you would have learned:

1. How to use CountingIdlingResource in Espresso tests.

1. Android Studio. The version used in this tutorial is Android Studio Chipmunk 2021.2.1 Patch 1.

1. Intermediate Android.
2. Basic Espresso.
3. Basic understanding of async operations.

To follow along with the tutorial, perform the steps below:

1. Create a new Android project with the default Empty Activity.

2. Add the dependencies below into your module build.gradle file.

    implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.6.1'
    implementation 'androidx.test.espresso:espresso-idling-resource:3.4.0'
    androidTestImplementation 'androidx.test:runner:1.4.0'
    androidTestImplementation 'androidx.test:rules:1.4.0'

3. Replace activity_main.xml with the code below. We simply changed the textSize and added an android:id to TextView.

    <?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_helloWorld"
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:text="Hello World!"
           android:textSize="32sp"
           app:layout_constraintBottom_toBottomOf="parent"
           app:layout_constraintEnd_toEndOf="parent"
           app:layout_constraintStart_toStartOf="parent"
           app:layout_constraintTop_toTopOf="parent" />
   
    </androidx.constraintlayout.widget.ConstraintLayout>

4. Replace the entire class ExampleInstrumentedTest with the code below. Besides the commented out lines, it is just a simple Espresso test that performs a click on the TextView, and then verifies that the new text content is correct. You do not have to understand the commented out parts for now.

    @RunWith(AndroidJUnit4::class)
    class ExampleInstrumentedTest {
   
       //Gets the IdlingRegistry singleton
       //private val idlingResourceRegistry = IdlingRegistry.getInstance()
   
       @get:Rule
       val activityRule = ActivityScenarioRule(MainActivity::class.java)
   
       @Test
       fun doAsyncTest(){
           //Register the CountingIdlingResource before click()
           //idlingResourceRegistry.register(countingIdlingResource)
   
           onView(withId(R.id.textView_helloWorld))
               .perform(click())
               .check(matches(withText("WorldHello!")))
       }
   
    /*    @After
       fun unregisterIdlingResources(){
           //Unregisters the CountingIdlingResource
           idlingResourceRegistry.resources.forEach {
               idlingResourceRegistry.unregister(it)
           }
       }*/
    }

5. Create a new class called HttpClient using the code below. This class contains a single function that will suspend for three seconds, and then assign a new text value to a TextView object.

    class HttpClient {
       fun doLongAsync(textView: TextView) {
           //Incrementing counter when work starts
           //countingIdlingResource.increment()
   
           CoroutineScope(Dispatchers.Main).launch {
               delay(3000)
               textView.text = "WorldHello!"
               //countingIdlingResource.decrement()
           }
       }
    }

6. In the same file, add the singleton below. You do not need to understand it for now.

    /*
    We can use a global singleton for this project because
    We don't have more than one test using this IdlingResourceCounter
    It is recommended to add IdlingResourceCounter directly into your
    Production code
    */
    object IdlingResourceCounter {
       private const val IDLING_RESOURCE_NAME = "GlobalIdlingResourceCounter"
       val countingIdlingResource = CountingIdlingResource(IDLING_RESOURCE_NAME)
    }

7. Finally, append the code below to MainActivity#onCreate().

    val textView = findViewById<TextView>(R.id.textView_helloWorld)
   
    val httpClient = HttpClient()
   
    textView.setOnClickListener {
       //Don't pass a View to a Service in a real app!
       httpClient.doLongAsync(it as TextView)
    }

The tutorial app contains a single TextView, after clicking on it and waits for 3 seconds, then its value will change to WorldHello! from Hello World!.

Now let us look at the instrument test doAsyncTest() in ExampleInstrumentedTest.

doAsyncTest() will fail because Espresso is not aware of the background task.

androidx.test.espresso.base.DefaultFailureHandler$AssertionFailedWithCauseError: 'an instance of android.widget.TextView and view.getText() with or without transformation to match: is "WorldHello!"' doesn't match the selected view.
Expected: an instance of android.widget.TextView and view.getText() with or without transformation to match: is "WorldHello!"

It tries to check for the WorldHello! value immediately after clicking on the TextView. There are only three conditions where Espresso will wait:

1. The MessageQueue is empty.
2. There is no running AsyncTask.
3. There is no idling resource. CountingIdlingResource is one of such resources that we are learning about in this tutorial.

The object IdlingResourceCounter contains a public field called countingIdlingResource, which is an instance of CountingIdlingResource. The only argument that the CountingIdlingResource constructor requires is a String value that explains what the instance of CountingIdlingResource is used for.

object IdlingResourceCounter {
    private const val IDLING_RESOURCE_NAME = "GlobalIdlingResourceCounter"
    val countingIdlingResource = CountingIdlingResource(IDLING_RESOURCE_NAME)
}

We are only able to use a global object in this tutorial because we only have one test. It is recommended that you provide a CountingIdlingResource for each instance of your async-worker class.

Your Service or Repository classes should increment() the counter when starting long-running async work and decrement() the counter when the work is complete. To achieve this, uncomment the respective lines in the HttpClient class, so it should look like the code below.

class HttpClient {
   fun doLongAsync(textView: TextView) {
       //Incrementing counter when work starts
       countingIdlingResource.increment()

       CoroutineScope(Dispatchers.Main).launch {
           delay(3000)
           textView.text = "WorldHello!"
           countingIdlingResource.decrement()
       }
   }
}

Simply having a working CountingIdlingResource is not enough. We still have to register the CountingIdlingResource instance to the IdlingResourceRegistry. IdlingResourceRegistry is a singleton. We already have the code to retrieve it in ExampleInstrumentedTest, so retrieve it by uncomment the line of code below.

private val idlingResourceRegistry = IdlingRegistry.getInstance()

Now that we have the IdlingResourceRegistry, we can register CountingIdlingResource to it by uncommenting this line of code inside doAsyncTest().

idlingResourceRegistry.register(countingIdlingResource)

We also have to unregister the idling resource after the test is done, so uncomment the function unregisterIdlingResources() as well.

@After
fun unregisterIdlingResources(){
   //Unregisters the CountingIdlingResource
   idlingResourceRegistry.resources.forEach {
       idlingResourceRegistry.unregister(it)
   }
}

We should have everything we need for a working test. If we run the test now, we can see that Espresso will wait for 3 seconds before performing the check().

ExampleInstrumentedTest.kt

@RunWith(AndroidJUnit4::class)
class ExampleInstrumentedTest {

   //Gets the IdlingRegistry singleton
   private val idlingResourceRegistry = IdlingRegistry.getInstance()

   @get:Rule
   val activityRule = ActivityScenarioRule(MainActivity::class.java)

   @Test
   fun doAsyncTest(){
       //Register the CountingIdlingResource before click()
       idlingResourceRegistry.register(countingIdlingResource)

       onView(withId(R.id.textView_helloWorld))
           .perform(click())
           .check(matches(withText("WorldHello!")))
   }

   @After
   fun unregisterIdlingResources(){
       //Unregisters the CountingIdlingResource
       idlingResourceRegistry.resources.forEach {
           idlingResourceRegistry.unregister(it)
       }
   }
}

HttpClient.kt

class HttpClient {
   fun doLongAsync(textView: TextView) {
       //Incrementing counter when work starts
       countingIdlingResource.increment()

       CoroutineScope(Dispatchers.Main).launch {
           delay(3000)
           textView.text = "WorldHello!"
           countingIdlingResource.decrement()
       }
   }
}

/*
We can use a global singleton for this project because
We don't have more than one test using this IdlingResourceCounter
It is recommended to add IdlingResourceCounter directly into your
Production code
*/
object IdlingResourceCounter {
   private const val IDLING_RESOURCE_NAME = "GlobalIdlingResourceCounter"
   val countingIdlingResource = CountingIdlingResource(IDLING_RESOURCE_NAME)
}

MainActivity.kt

class MainActivity : AppCompatActivity() {
   override fun onCreate(savedInstanceState: Bundle?) {
       super.onCreate(savedInstanceState)
       setContentView(R.layout.activity_main)

       val textView = findViewById<TextView>(R.id.textView_helloWorld)

       val httpClient = HttpClient()

       textView.setOnClickListener {
           //Don't pass a View to a Service in a real app!
           httpClient.doLongAsync(it as TextView)
       }
   }
}

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_helloWorld"
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:text="Hello World!"
       android:textSize="32sp"
       app:layout_constraintBottom_toBottomOf="parent"
       app:layout_constraintEnd_toEndOf="parent"
       app:layout_constraintStart_toStartOf="parent"
       app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

Module build.gradle

plugins {
   id 'com.android.application'
   id 'org.jetbrains.kotlin.android'
}

android {
   compileSdk 32

   defaultConfig {
       applicationId "com.example.daniwebandroidcountingidlingresource"
       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:1.6.0'
   implementation 'androidx.constraintlayout:constraintlayout:2.1.4'
   implementation 'androidx.test.espresso:espresso-idling-resource:3.4.0'
   testImplementation 'junit:junit:4.13.2'
   androidTestImplementation 'androidx.test.ext:junit:1.1.3'
   androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
   androidTestImplementation 'androidx.test:runner:1.4.0'
   androidTestImplementation 'androidx.test:rules:1.4.0'
   implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.6.1'

}

We have learned how to use CountingIdlingResource to make Espresso wait in this tutorial. The full project code can be found at https://github.com/dmitrilc/DaniwebAndroidCountingIdlingResource.

Proficient with Flutter
Experience with Flutter/Native hybrid development
Experience in the development of multiple Flutter projects, including the launch of Flutter projects
Email: tianxzhang@163.coma

Hey guys is there a way to intercept shut down to make the user enter password if the state is in the locked state? Its just that I am engineering an anti-theft app and would to disable shut down from lock screen while the device is in the locked state. Is there a way of achieving this with Android Java. I tried listening on the shut down intent but the device does not even give the code in the OnRecieve to execute

Starting from Android 10 (API 29), Android places many restrictions on how apps can launch activities from the background.

There are a couple of exemptions, which can be found on this list. At the end of the list is the usage of the dangerous permission SYSTEM_ALERT_WINDOW. I have seen this permission recommended elsewhere, but usage of this permission is unnecessary to show an Activity for an alarm application and violates best practices for Android permission. Even the stock Clock app does not require this permission, the only install-time permission that it needs is SCHEDULE_EXACT_ALARM.

The correct way to show an Activity with an alarm is by using a notification with a full-screen Intent.

At the end of the tutorial, you would have learned:

1. How to schedule an exact alarm.
2. How to show an Activity on the lock screen even if the screen is off and the Activity destroyed.

1. Android Studio. The version used in this tutorial is Android Studio Chipmunk 2021.2.1.

1. Intermediate Android.
2. Notification.
3. BroadcastReceiver.

To follow along with the tutorial, perform the steps below:

1. Create a new Android project with the default Empty Activity.

2. Add the <string> resource below into strings.xml.

    <string name="schedule_alarm">Schedule Alarm</string>

3. Replace the code in activity_main.xml with the code below. This replaces the default TextView with a Button.

    <?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_scheduleAlarm"
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:text="@string/schedule_alarm"
           app:layout_constraintBottom_toBottomOf="parent"
           app:layout_constraintEnd_toEndOf="parent"
           app:layout_constraintStart_toStartOf="parent"
           app:layout_constraintTop_toTopOf="parent" />
    </androidx.constraintlayout.widget.ConstraintLayout>

Although there are many types of alarms that you can set on Android, for this tutorial, knowing that we are only working with exact alarms is enough. Android allows other types of inexact alarms, which are not relevant for this tutorial. To set an exact alarm, you can use the method setAlarmClock() from the AlarmManager class.

You can retrieve an instance of AlarmManager inside your Activity by calling getSystemService().

To be able to set an exact alarm and show the Activity on the lock screen when the device is sleeping, there are quite a few steps involved. The list below provides a quick summary.

1. The application must be ready to show a notification on high priority, so we must create a NotificationChannel with IMPORTANTCE_HIGH.
2. The AlarmManager cannot show the Activity directly, so it must go through a BroadcastReceiver, which will then displays a Notification that can show an Activity.
   
3. Install-time permissions and proper attributes for the Activity must be set in the manifest.

Now that we have a rough idea of what to do next, it is time to write some code.

1. Add the constants above on top of MainActivity.kt. These are just convenient constants for the NotificationManager.

    private const val NOTIFICATION_CHANNEL_NAME = "0"
    const val NOTIFICATION_CHANNEL_ID = "1"

2. Add the function to create the NotificationChannel to MainActivity.

    private fun createNotificationChannel(){
       if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
           val channel = NotificationChannel(
               NOTIFICATION_CHANNEL_ID,
               NOTIFICATION_CHANNEL_NAME,
               NotificationManager.IMPORTANCE_HIGH
           )
   
           with(getSystemService(NOTIFICATION_SERVICE) as NotificationManager){
               createNotificationChannel(channel)
           }
       }
    }

3. Finally, call it in onCreate().

    createNotificationChannel()

Next, we will have to bind the Button to schedule an exact alarm.

1. Append the code below to onCreate() to find the Button and binds its onClickListener.

    findViewById<Button>(R.id.button_scheduleAlarm).setOnClickListener {
    }

2. We will have to add FLAG_IMMUTABLE to all PendingIntent created in this tutorial, so add the constant below above MainActivity.kt

    val compatFlags = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
       FLAG_IMMUTABLE
    } else {
       0
    }

3. Add the code below inside the setOnClickListener() callback. This code creates the explicit Intent as well as wrapping it in a PendingIntent, which is required later by AlarmClockInfo. Ignores the compile error because of the missing AlarmReceiver for now.

    val sendBroadcastIntent = Intent(this, AlarmReceiver::class.java)
    val pendingIntent = PendingIntent.getBroadcast(
       this,
       0,
       sendBroadcastIntent,
       compatFlags
    )

4. Finally, retrieve the AlarmManager, and use setAlarmClock().

    with(getSystemService(Context.ALARM_SERVICE) as AlarmManager){
       //Alarm will trigger in 10 seconds
       //You should set the alarm by clicking the Button, and then clears the Activity
       // from the backstack by swiping up on the Recents screen.
       val triggerTime = Calendar.getInstance().apply {
           add(SECOND, 10)
       }
   
       val alarmInfo = AlarmManager.AlarmClockInfo(
           triggerTime.timeInMillis,
           pendingIntent //The alarm will fire this PendingIntent
       )
   
       setAlarmClock(
           alarmInfo,
           pendingIntent
       )
    }

We will now create a BroadcastReceiver called AlarmReceiver.

Copy and paste the entire code below into your project. Here, we created and show a Notification with a full-screen Intent.

import android.app.PendingIntent
import android.content.BroadcastReceiver
import android.content.Context
import android.content.Intent
import androidx.core.app.NotificationCompat
import androidx.core.app.NotificationManagerCompat

class AlarmReceiver : BroadcastReceiver() {
   override fun onReceive(context: Context?, intent: Intent?) {
       if (context != null){
           val fullScreenPendingIntent = PendingIntent.getActivity(
               context,
               0,
               Intent(context, MainActivity::class.java),
               compatFlags
           )

           val notificationBuilder = NotificationCompat.Builder(context, NOTIFICATION_CHANNEL_ID)
               .setSmallIcon(R.drawable.ic_launcher_foreground)
               .setPriority(NotificationCompat.PRIORITY_HIGH)
               .setFullScreenIntent(fullScreenPendingIntent, true)

           with(NotificationManagerCompat.from(context)) {
               //This notification only works once until the end user dismiss the previous notification.
               //Can also make the notification auto-dismiss if desired.
               notify(1, notificationBuilder.build())
           }
       }
   }
}

1. For the app to work, we will need to declare two install-time permissions, so add to the the manifest.

    <uses-permission android:name="android.permission.SCHEDULE_EXACT_ALARM" />
    <uses-permission android:name="android.permission.USE_FULL_SCREEN_INTENT"/>

2. For MainActivity, we will need to add the showWhenLocked and turnScreenOn attributes.

    android:showWhenLocked="true"
    android:turnScreenOn="true"

3. Finally, declare the BroadcastReceiver AlarmReceiver.

    <receiver
       android:name=".AlarmReceiver"
       android:exported="false"/>

If you ran the app previously on your device, completely uninstall it and install it again.

To test if the app is working correctly, follow the steps below:

1. Starts the app.
2. Press the Button to schedule an alarm.
3. Immediately kills the app from the Recents screen.
4. Put the device into sleep.
5. Wait a couple of seconds. Remember that you only have ten seconds to perform steps 2-4.
6. Wait for the app to show on the home screen. Home screen is still locked for obvious security reasons.

You can use the animation below as reference.

MainActivity.kt

private const val NOTIFICATION_CHANNEL_NAME = "0"
const val NOTIFICATION_CHANNEL_ID = "1"

val compatFlags = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
   FLAG_IMMUTABLE
} else {
   0
}

class MainActivity : AppCompatActivity() {
   override fun onCreate(savedInstanceState: Bundle?) {
       super.onCreate(savedInstanceState)
       setContentView(R.layout.activity_main)

       createNotificationChannel()

       findViewById<Button>(R.id.button_scheduleAlarm).setOnClickListener {
           val sendBroadcastIntent = Intent(this, AlarmReceiver::class.java)
           val pendingIntent = PendingIntent.getBroadcast(
               this,
               0,
               sendBroadcastIntent,
               compatFlags
           )

           with(getSystemService(Context.ALARM_SERVICE) as AlarmManager){
               //Alarm will trigger in 10 seconds
               //You should set the alarm by clicking the Button, and then clears the Activity
               // from the backstack by swiping up on the Recents screen.
               val triggerTime = Calendar.getInstance().apply {
                   add(SECOND, 10)
               }

               val alarmInfo = AlarmManager.AlarmClockInfo(
                   triggerTime.timeInMillis,
                   pendingIntent //The alarm will fire this PendingIntent
               )

               setAlarmClock(
                   alarmInfo,
                   pendingIntent
               )
           }
       }
   }

   private fun createNotificationChannel(){
       if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
           val channel = NotificationChannel(
               NOTIFICATION_CHANNEL_ID,
               NOTIFICATION_CHANNEL_NAME,
               NotificationManager.IMPORTANCE_HIGH
           )

           with(getSystemService(NOTIFICATION_SERVICE) as NotificationManager){
               createNotificationChannel(channel)
           }
       }
   }
}

AlarmReceiver.kt

class AlarmReceiver : BroadcastReceiver() {
   override fun onReceive(context: Context?, intent: Intent?) {
       if (context != null){
           val fullScreenPendingIntent = PendingIntent.getActivity(
               context,
               0,
               Intent(context, MainActivity::class.java),
               compatFlags
           )

           val notificationBuilder = NotificationCompat.Builder(context, NOTIFICATION_CHANNEL_ID)
               .setSmallIcon(R.drawable.ic_launcher_foreground)
               .setPriority(NotificationCompat.PRIORITY_HIGH)
               .setFullScreenIntent(fullScreenPendingIntent, true)

           with(NotificationManagerCompat.from(context)) {
               //This notification only works once until the end user dismiss the previous notification.
               //Can also make the notification auto-dismiss if desired.
               notify(1, notificationBuilder.build())
           }
       }
   }
}

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_scheduleAlarm"
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:text="@string/schedule_alarm"
       app:layout_constraintBottom_toBottomOf="parent"
       app:layout_constraintEnd_toEndOf="parent"
       app:layout_constraintStart_toStartOf="parent"
       app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

strings.xml

<resources>
   <string name="app_name">Daniweb Android Native AlarmManager</string>
   <string name="schedule_alarm">Schedule Alarm</string>
</resources>

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:tools="http://schemas.android.com/tools"
   package="com.example.daniwebandroidnativealarmmanager">

   <uses-permission android:name="android.permission.SCHEDULE_EXACT_ALARM" />
   <uses-permission android:name="android.permission.USE_FULL_SCREEN_INTENT"/>

   <application
       android:allowBackup="true"
       android:dataExtractionRules="@xml/data_extraction_rules"
       android:fullBackupContent="@xml/backup_rules"
       android:icon="@mipmap/ic_launcher"
       android:label="@string/app_name"
       android:roundIcon="@mipmap/ic_launcher_round"
       android:supportsRtl="true"
       android:theme="@style/Theme.DaniwebAndroidNativeAlarmManager"
       tools:targetApi="31">
       <activity
           android:name=".MainActivity"
           android:showWhenLocked="true"
           android:turnScreenOn="true"
           android:exported="true">
           <intent-filter>
               <action android:name="android.intent.action.MAIN" />

               <category android:name="android.intent.category.LAUNCHER" />
           </intent-filter>
       </activity>
       <receiver
           android:name=".AlarmReceiver"
           android:exported="false"/>
   </application>

</manifest>

We have learned how to launch an Activity from an exact alarm in this tutorial. Please keep in mind that this tutorial was only tested on Android API 32. The full project code can be found at https://github.com/dmitrilc/DaniwebAndroidNativeAlarmManager.

In this tutorial, we will learn how to use ConcatAdapter. It is a great choice for displaying header or footer at the beginning or at the end of a RecyclerView.

At the end of the tutorial, you would have learned:

1. How to use ConcatAdapter to combine Adapters.

1. Android Studio. The version used in this tutorial is Android Studio Chipmunk 2021.2.1.

1. Basic Android.
2. RecyclerView.

To follow along with the tutorial, perform the steps below:

1. Create a new Android project with the default Empty Activity.

2. Replace the content of activity_main.xml with the code below. This removes the default Hello World TextView and add a RecyclerView that is constrained to the parent.

    <?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"
           android:layout_width="match_parent"
           android:layout_height="match_parent"
           app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
           app:layout_constraintBottom_toBottomOf="parent"
           app:layout_constraintEnd_toEndOf="parent"
           app:layout_constraintStart_toStartOf="parent"
           app:layout_constraintTop_toTopOf="parent" />
    </androidx.constraintlayout.widget.ConstraintLayout>

3. Create a new layout resource called text_holder.xml to contain the view for the first ViewHolder.

    <?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="wrap_content">
   
       <TextView
           android:id="@+id/textView_holder"
           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_toTopOf="parent"
           tools:text="Text Holder Content" />
    </androidx.constraintlayout.widget.ConstraintLayout>

4. Add the vector image below as a drawable resource using the name ic_android_black_24dp.

    <vector android:height="24dp" android:tint="#000000"
       android:viewportHeight="24" android:viewportWidth="24"
       android:width="24dp" xmlns:android="http://schemas.android.com/apk/res/android">
       <path android:fillColor="#FF000000" android:pathData="M17.6,11.48 L19.44,8.3a0.63,0.63 0,0 0,-1.09 -0.63l-1.88,3.24a11.43,11.43 0,0 0,-8.94 0L5.65,7.67a0.63,0.63 0,0 0,-1.09 0.63L6.4,11.48A10.81,10.81 0,0 0,1 20L23,20A10.81,10.81 0,0 0,17.6 11.48ZM7,17.25A1.25,1.25 0,1 1,8.25 16,1.25 1.25,0 0,1 7,17.25ZM17,17.25A1.25,1.25 0,1 1,18.25 16,1.25 1.25,0 0,1 17,17.25Z"/>
    </vector>

5. Create another layout resource file called image_holder.xml for the second ViewHolder.

    <?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"
       android:layout_width="match_parent"
       android:layout_height="wrap_content">
   
       <ImageView
           android:id="@+id/imageView_holder"
           android:layout_width="match_parent"
           android:layout_height="50dp"
           android:src="@drawable/ic_android_black_24dp"
           app:layout_constraintBottom_toBottomOf="parent"
           app:layout_constraintEnd_toEndOf="parent"
           app:layout_constraintStart_toStartOf="parent"
           app:layout_constraintTop_toTopOf="parent" />
    </androidx.constraintlayout.widget.ConstraintLayout>

6. Create a TextAdapter class to display text_holder_xml.

    class TextAdapter(private val dataSet: List<String>) : RecyclerView.Adapter<TextAdapter.TextViewHolder>() {
   
       class TextViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView){
           val textView: TextView = itemView.findViewById(R.id.textView_holder)
       }
   
       override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): TextViewHolder {
           val view = LayoutInflater.from(parent.context)
               .inflate(R.layout.text_holder, parent, false)
   
           return TextViewHolder(view)
       }
   
       override fun onBindViewHolder(holder: TextViewHolder, position: Int) {
           holder.textView.text = dataSet[position]
       }
   
       override fun getItemCount() = dataSet.size
    }

7. Create an ImageHolder class to display image_holder.xml.

    class ImageAdapter : RecyclerView.Adapter<ImageAdapter.ImageViewHolder>() {
   
       class ImageViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView)
   
       override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ImageViewHolder {
           val view = LayoutInflater.from(parent.context)
               .inflate(R.layout.image_holder, parent, false)
   
           return ImageViewHolder(view)
       }
   
       override fun onBindViewHolder(holder: ImageViewHolder, position: Int) {}
       override fun getItemCount() = 1
    }

8. Replace the code in MainActivity with the code below. This implementation of onCreate() creates data for the separate Adapters and assign them to the RecyclerView. Only one Adapter can be assigned to a RecyclerView, so the last one that is assigned wins.

    class MainActivity : AppCompatActivity() {
       override fun onCreate(savedInstanceState: Bundle?) {
           super.onCreate(savedInstanceState)
           setContentView(R.layout.activity_main)
   
           //list of strings
           val textDataSet = alphabet
               .map { "$it" }
   
           val recycler = findViewById<RecyclerView>(R.id.recycler)
           recycler.adapter = TextAdapter(textDataSet)
           recycler.adapter = ImageAdapter()
       }
   
       companion object {
           private val alphabet = CharRange('A', 'Z')
       }
    }

9. Add the dependency for the latest version of RecyclerView to your project build.gradle file. ConcatAdapter is only included from version 1.2.0-alpha04 (it used to be called MergeAdapter).

    implementation "androidx.recyclerview:recyclerview:1.2.1"

As of right now, there are two lines of code that create an assign an Adapter to the RecyclerView. The app will look different depending on which Adapter you decide to use.

If you comment out the line below,

recycler.adapter = ImageAdapter(imageDataSet)

then your RecyclerView will use the TextAdapter.

If you just leave the code as-is, letting the ImageAdapter wins, then the RecyclerView will just use the ImageAdapter as its adapter. The ImageAdapter will only display one item.

ConcatAdapter is typically used for displaying multiple Adapters one after another, this does not mean that the Adapters are interweaving into one another.

1. Comment out the current assignments to Adapter.

    // recycler.adapter = TextAdapter(textDataSet)
    // recycler.adapter = ImageAdapter()

2. Using a ConcatAdapter is fairly simple, you can just add the other Adapters into the ConcatAdapter constructor.

    recycler.adapter = ConcatAdapter(
       TextAdapter(textDataSet),
       ImageAdapter()
    )

If we run the App now, it will look like the image below.

If you want to dynamically add or remove the child Adapters, you can also instantiate an empty ConcatAdapter, and then call addAdapter() or removeAdapter() as needed. You can also add another Adapter of the same type again if your use case needs it.

//Dynamically add or more Adapters
val concatAdapter = ConcatAdapter()
   .apply {
       addAdapter(TextAdapter(textDataSet))
       addAdapter(ImageAdapter())
       addAdapter(TextAdapter(textDataSet))
       addAdapter(ImageAdapter())
   }

recycler.adapter = concatAdapter

MainActivity.kt

class MainActivity : AppCompatActivity() {
   override fun onCreate(savedInstanceState: Bundle?) {
       super.onCreate(savedInstanceState)
       setContentView(R.layout.activity_main)

       //list of strings
       val textDataSet = alphabet
           .map { "$it" }

       val recycler = findViewById<RecyclerView>(R.id.recycler)
//        recycler.adapter = TextAdapter(textDataSet)
//        recycler.adapter = ImageAdapter()

       //Use ConcatAdapter constructor
/*        recycler.adapter = ConcatAdapter(
           TextAdapter(textDataSet),
           ImageAdapter()
       )*/

       //Dynamically add or more Adapters
       val concatAdapter = ConcatAdapter()
           .apply {
               addAdapter(TextAdapter(textDataSet))
               addAdapter(ImageAdapter())
               addAdapter(TextAdapter(textDataSet))
               addAdapter(ImageAdapter())
           }

       recycler.adapter = concatAdapter
   }

   companion object {
       private val alphabet = CharRange('A', 'Z')
   }
}

ImageAdapter.kt

class ImageAdapter : RecyclerView.Adapter<ImageAdapter.ImageViewHolder>() {

   class ImageViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView)

   override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ImageViewHolder {
       val view = LayoutInflater.from(parent.context)
           .inflate(R.layout.image_holder, parent, false)

       return ImageViewHolder(view)
   }

   override fun onBindViewHolder(holder: ImageViewHolder, position: Int) {}
   override fun getItemCount() = 1
}

TextAdapter.kt

class TextAdapter(private val dataSet: List<String>) : RecyclerView.Adapter<TextAdapter.TextViewHolder>() {

   class TextViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView){
       val textView: TextView = itemView.findViewById(R.id.textView_holder)
   }

   override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): TextViewHolder {
       val view = LayoutInflater.from(parent.context)
           .inflate(R.layout.text_holder, parent, false)

       return TextViewHolder(view)
   }

   override fun onBindViewHolder(holder: TextViewHolder, position: Int) {
       holder.textView.text = dataSet[position]
   }

   override fun getItemCount() = dataSet.size
}

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"
       android:layout_width="match_parent"
       android:layout_height="match_parent"
       app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
       app:layout_constraintBottom_toBottomOf="parent"
       app:layout_constraintEnd_toEndOf="parent"
       app:layout_constraintStart_toStartOf="parent"
       app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

image_holder.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"
   android:layout_width="match_parent"
   android:layout_height="wrap_content">

   <ImageView
       android:id="@+id/imageView_holder"
       android:layout_width="match_parent"
       android:layout_height="50dp"
       android:src="@drawable/ic_android_black_24dp"
       app:layout_constraintBottom_toBottomOf="parent"
       app:layout_constraintEnd_toEndOf="parent"
       app:layout_constraintStart_toStartOf="parent"
       app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

text_holder.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="wrap_content">

   <TextView
       android:id="@+id/textView_holder"
       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_toTopOf="parent"
       tools:text="Text Holder Content" />
</androidx.constraintlayout.widget.ConstraintLayout>

Project build.gradle

plugins {
   id 'com.android.application'
   id 'org.jetbrains.kotlin.android'
}

android {
   compileSdk 32

   defaultConfig {
       applicationId "com.example.daniwebandroidconcatadapter"
       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.recyclerview:recyclerview:1.2.1"
   implementation 'androidx.core:core-ktx:1.7.0'
   implementation 'androidx.appcompat:appcompat:1.4.1'
   implementation 'com.google.android.material:material:1.6.0'
   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 ConcatAdapter in this tutorial. The full project code can be found at https://github.com/dmitrilc/DaniwebAndroidConcatAdapter.

Rather than modifying the button widgets appearance in code, it is possible to do this in an XML resource instead. In this tutorial, we will learn how to create two different types of specialized XML resource files for changing the Drawable and the color.

At the end of the tutorial, you would have learned:

1. How to use a Color State List resource.
2. How to use a Drawable State List resource.

1. Android Studio. The version used in this tutorial is Android Studio Chipmunk 2021.2.1.

1. Basic Android.

To follow along with the tutorial, perform the steps below:

1. Create a new Android project with the default Empty Activity.

2. Add the vector resource below as ic_baseline_arrow_24.xml into drawable.

    <vector android:height="24dp" android:tint="#000000"
       android:viewportHeight="24" android:viewportWidth="24"
       android:width="24dp" xmlns:android="http://schemas.android.com/apk/res/android">
       <path android:fillColor="@android:color/white" android:pathData="M8,5v14l11,-7z"/>
    </vector>

3. Replace the code inside of activity_main.xml with the code below. The screen will now contain a single ImageButton for us to play with.

    <?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">
   
       <ImageButton
           android:id="@+id/imageButton"
           android:layout_width="200dp"
           android:layout_height="200dp"
           android:backgroundTint="#00FFFFFF"
           android:scaleType="fitCenter"
           app:layout_constraintBottom_toBottomOf="parent"
           app:layout_constraintEnd_toEndOf="parent"
           app:layout_constraintStart_toStartOf="parent"
           app:layout_constraintTop_toTopOf="parent"
           app:srcCompat="@drawable/ic_baseline_play_arrow_24" />
    </androidx.constraintlayout.widget.ConstraintLayout>

4. If we run the app now, it should look like the screenshot below.

Conceptually, a state list resource is an XML file that tells Android what to do when a widget is in a certain state. For Button-type widgets, the common states are focused, pressed, and none.

Let us create the XML file first and dissect the syntax later.

1. Right-click on res -> New -> Android Resource File.

2. Select the *Resource type as Color. The root element must be selector. Finally use color as the Directory name**.
   

3. Copy and paste the code below into the button_colors.xml file.

    <?xml version="1.0" encoding="utf-8"?>
    <selector xmlns:android="http://schemas.android.com/apk/res/android">
       <item android:color="@color/purple_700"
           android:state_pressed="true"/>
       <item android:color="@color/purple_700"
           android:state_focused="true" />
       <item android:color="@color/black" />
    </selector>

4. Now that we have a resource file, it is time to discuss the syntax. There are only a couple of simple rules.
   a. The root element of a state list resource file must be <selector>.
   b. Every child item is an <item>.
   c. Every <item> must have an android:color attribute.
   d. The android:state_X attributes define whether you want this color to be active when the button is in a specific state. e. Here, we configure for purple_700 to be active when the button is either in the focused or pressed states. When it is not focused or pressed, it takes on the color black.

To apply these color states to our Play button, we can add an app:tint attribute directly to the ImageButton widget in the activity_main.xml. The value for this attribute is the path to the color state list button_colors.xml.

app:tint="@color/button_colors"

If we run the app and test the button, it should change its color on click.

Besides a Color State List, Android provides of state list that is called Drawable State List. The concept is very similar to the Color State List. You define an XML resource that tells Android which Drawable to use for the widget.

1. To create a Drawable state list, follow the steps above to create an XML resource, but select Drawable as the Resource type instead. The root element remains <selector>. The directory name should be drawable.
   

2. Add another vector resource called ic_baseline_pause_24.xml for this step.

    <vector android:height="24dp" android:tint="#000000"
       android:viewportHeight="24" android:viewportWidth="24"
       android:width="24dp" xmlns:android="http://schemas.android.com/apk/res/android">
       <path android:fillColor="@android:color/white" android:pathData="M6,19h4L10,5L6,5v14zM14,5v14h4L18,5h-4z"/>
    </vector>

3. Replace the content of button_drawables.xml with the code below. This will load the vector image created previously when the button is pressed.

    <?xml version="1.0" encoding="utf-8"?>
    <selector xmlns:android="http://schemas.android.com/apk/res/android">
       <item android:drawable="@drawable/ic_baseline_pause_24"
           android:state_pressed="true" />
       <item android:drawable="@drawable/ic_baseline_play_arrow_24" />
    </selector>

4. Back in activity_main.xml, replace the value of app:srcCompat to reference the new Drawable State List instead of the direct vector image.

    app:srcCompat="@drawable/button_drawables"

If we run the app now, we can see that both the color and Drawable are changed when the button is pressed.

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">

   <ImageButton
       android:id="@+id/imageButton"
       android:layout_width="200dp"
       android:layout_height="200dp"
       android:backgroundTint="#00FFFFFF"
       android:scaleType="fitCenter"
       app:layout_constraintBottom_toBottomOf="parent"
       app:layout_constraintEnd_toEndOf="parent"
       app:layout_constraintStart_toStartOf="parent"
       app:layout_constraintTop_toTopOf="parent"
       app:srcCompat="@drawable/button_drawables"
       app:tint="@color/button_colors" />
</androidx.constraintlayout.widget.ConstraintLayout>

button_drawables.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
   <item android:drawable="@drawable/ic_baseline_pause_24"
       android:state_pressed="true" />
   <item android:drawable="@drawable/ic_baseline_play_arrow_24" />
</selector>

button_colors.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
   <item android:color="@color/purple_700"
       android:state_pressed="true"/>
   <item android:color="@color/purple_700"
       android:state_focused="true" />
   <item android:color="@color/black" />
</selector>

ic_baseline_pause_24.xml

<vector android:height="24dp" android:tint="#000000"
   android:viewportHeight="24" android:viewportWidth="24"
   android:width="24dp" xmlns:android="http://schemas.android.com/apk/res/android">
   <path android:fillColor="@android:color/white" android:pathData="M6,19h4L10,5L6,5v14zM14,5v14h4L18,5h-4z"/>
</vector>

ic_baseline_play_arrow_24

<vector android:height="24dp" android:tint="#000000"
   android:viewportHeight="24" android:viewportWidth="24"
   android:width="24dp" xmlns:android="http://schemas.android.com/apk/res/android">
   <path android:fillColor="@android:color/white" android:pathData="M8,5v14l11,-7z"/>
</vector>

We have learned how to change button color and drawables using state lists in this tutorial. The full project code can be found at https://github.com/dmitrilc/DaniwebModifyButtonColorUsingColorStateListResource.

The Android platform provides many different types of menus to be added to an Android app. In this tutorial, we will learn how to add Contextual Menus to our app.

At the end of the tutorial, you would have learned:

1. How to add a floating contextual menu.
2. How to add a contextual menu in action mode.

1. Android Studio. The version used in this tutorial is Bumblebee 2021.1.1 Patch 3.

1. Basic Android.
2. Menu XML resource.

To follow along with the tutorial, perform the steps below:

1. Create a new Android project with the default Empty Activity.

2. Give the default TextView an android:id of hello and android:textSize of 32sp.

3. Your activity_main.xml should look like 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">
   
       <TextView
           android:id="@+id/hello"
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:text="@string/hello_world"
           android:textSize="32sp"
           app:layout_constraintBottom_toBottomOf="parent"
           app:layout_constraintLeft_toLeftOf="parent"
           app:layout_constraintRight_toRightOf="parent"
           app:layout_constraintTop_toTopOf="parent" />
   
    </androidx.constraintlayout.widget.ConstraintLayout>

4. Add the string resources below into your strings.xml file.

    <string name="shuffle">Shuffle</string>
    <string name="reset">Reset</string>
    <string name="insert_random">Insert Random</string>
    <string name="hello_world">Hello World!</string>

5. Add a menu XML resource called contextual.xml under res/menu. This will represent a menu with 3 options, Shuffle, Reset, and Insert Random. Later on, these actions will be performed on the default TextView.

    <?xml version="1.0" encoding="utf-8"?>
    <menu xmlns:android="http://schemas.android.com/apk/res/android">
   
       <item
           android:id="@+id/shuffle"
           android:title="@string/shuffle" />
       <item
           android:id="@+id/reset"
           android:title="@string/reset" />
       <item
           android:id="@+id/insert_random"
           android:title="@string/insert_random" />
    </menu>

A Contextual Menu can operate in two different modes:

1. floating contextual menu: a floating menu appears on the screen after long-clicking a View. The floating menu uses this View as an anchor.
   

2. contextual action mode menu: the menu appears in the Action Bar instead, showing menu items as actions.

To add a floating contextual menu, follow the steps below:

1. In MainActivitys onCreate(), retrieve the default TextView.

    val textView = findViewById<TextView>(R.id.hello)

2. Next, we will have to register this View for a contextual menu by calling registerForContextMenu() and passing in this same View.

    //Contextual floating menu
    registerForContextMenu(textView)

3. Now, we need to override MainActivitys onCreateContextMenu() method, and inflate the menu resource file contextual.xml here.

    override fun onCreateContextMenu(
       menu: ContextMenu?,
       v: View?,
       menuInfo: ContextMenu.ContextMenuInfo?
    ) {
       super.onCreateContextMenu(menu, v, menuInfo)
       menuInflater.inflate(R.menu.contextual, menu)
    }

4. The floating contextual menu should be working if you run the app now, but let us add some behaviors to the menu items to make them useful. We can listen for the floating contextual menus item clicks in onContextItemSelected().

    override fun onContextItemSelected(item: MenuItem): Boolean {
       super.onContextItemSelected(item)
       return handleContextMenuItem(item)
    }

5. Because we will reuse the logic to handle the menu items later on in the tutorial, we will extract this logic into a different function called handleContextMenuItem(). This function will shuffle, reset, or insert a random alphabet character at a random index to Textview.

    private fun handleContextMenuItem(item: MenuItem): Boolean {
       val textView = findViewById<TextView>(R.id.hello)
       val text = textView.text
   
       return when(item.itemId){
           R.id.shuffle -> {
               textView.text = text
                   .asSequence()
                   .shuffled()
                   .joinToString(separator = "") {
                       "$it"
                   }
               true
           }
           R.id.reset -> {
               textView.text = getString(R.string.hello_world)
               true
           }
           R.id.insert_random -> {
               textView.text = StringBuilder(text)
                   .insert(
                       text.indices.random(),
                       alphabet.random()
                   )
               true
           }
           else -> false
       }
    }

6. Also, add the companion object below for the alphabet constant.

    companion object {
       //Don't want chars 91->96
       private val alphabet = CharRange('A', 'Z').plus(CharRange('a', 'z'))
    }

We are now done with the floating contextual menu. The app should behave similarly to the animation below.

In this section, we will learn how to add a contextual menu in action mode.

1. Comment out registerForContextMenu(textView) in onCreate() as we will not be using the floating action menu anymore.

2. Implement the ActionMode.Callback interface. This callback allows you to inflate, listen to click and destroy events, etc.

    private val actionModeCallback = object : ActionMode.Callback {
       override fun onCreateActionMode(mode: ActionMode, menu: Menu): Boolean {
           menuInflater.inflate(R.menu.contextual, menu)
           return true
       }
   
       override fun onActionItemClicked(mode: ActionMode, item: MenuItem): Boolean {
           return handleContextMenuItem(item)
       }
   
       override fun onPrepareActionMode(mode: ActionMode, menu: Menu) = false
       override fun onDestroyActionMode(mode: ActionMode) {}
    }

3. In onCreateActionMode(), we inflate the menu XML resource as done previously in onCreateContextMenu. Because actionModeCallback is declared inside the MainActivity scope, we have access to the menuInflater in the callback as well. If your implementation of ActionMode.Callback is outside of MainActivity, then you can access a MenuInflater from the ActionMode parameter instead.

4. Back in onCreate(), we can bind the TextViews OnLongClickListener to invoke a function called startActionMode().

    //Contextual action menu
    textView.setOnLongClickListener {
       startActionMode(actionModeCallback)
       true
    }

When we run the app now, we should get a contextual menu in Action Bar instead of a floating contextual menu.

MainActivity.kt

class MainActivity : AppCompatActivity() {

   private val actionModeCallback = object : ActionMode.Callback {
       override fun onCreateActionMode(mode: ActionMode, menu: Menu): Boolean {
           menuInflater.inflate(R.menu.contextual, menu)
           return true
       }

       override fun onActionItemClicked(mode: ActionMode, item: MenuItem): Boolean {
           return handleContextMenuItem(item)
       }

       override fun onPrepareActionMode(mode: ActionMode, menu: Menu) = false
       override fun onDestroyActionMode(mode: ActionMode) {}
   }

   override fun onCreate(savedInstanceState: Bundle?) {
       super.onCreate(savedInstanceState)
       setContentView(R.layout.activity_main)

       val textView = findViewById<TextView>(R.id.hello)

       //Contextual floating menu
       //registerForContextMenu(textView)

       //Contextual action menu
       textView.setOnLongClickListener {
           startActionMode(actionModeCallback)
           true
       }
   }

   override fun onCreateContextMenu(
       menu: ContextMenu?,
       v: View?,
       menuInfo: ContextMenu.ContextMenuInfo?
   ) {
       super.onCreateContextMenu(menu, v, menuInfo)
       menuInflater.inflate(R.menu.contextual, menu)
   }

   override fun onContextItemSelected(item: MenuItem): Boolean {
       super.onContextItemSelected(item)
       return handleContextMenuItem(item)
   }

   private fun handleContextMenuItem(item: MenuItem): Boolean {
       val textView = findViewById<TextView>(R.id.hello)
       val text = textView.text

       return when(item.itemId){
           R.id.shuffle -> {
               textView.text = text
                   .asSequence()
                   .shuffled()
                   .joinToString(separator = "") {
                       "$it"
                   }
               true
           }
           R.id.reset -> {
               textView.text = getString(R.string.hello_world)
               true
           }
           R.id.insert_random -> {
               textView.text = StringBuilder(text)
                   .insert(
                       text.indices.random(),
                       alphabet.random()
                   )
               true
           }
           else -> false
       }
   }

   companion object {
       //Don't want chars 91->96
       private val alphabet = CharRange('A', 'Z').plus(CharRange('a', 'z'))
   }

}

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/hello"
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:text="@string/hello_world"
       android:textSize="32sp"
       app:layout_constraintBottom_toBottomOf="parent"
       app:layout_constraintLeft_toLeftOf="parent"
       app:layout_constraintRight_toRightOf="parent"
       app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

contextual.xml

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">

   <item
       android:id="@+id/shuffle"
       android:title="@string/shuffle" />
   <item
       android:id="@+id/reset"
       android:title="@string/reset" />
   <item
       android:id="@+id/insert_random"
       android:title="@string/insert_random" />
</menu>

**strings.xml**

<resources>
   <string name="app_name">Daniweb Android Contextual Menu</string>
   <string name="shuffle">Shuffle</string>
   <string name="reset">Reset</string>
   <string name="insert_random">Insert Random</string>
   <string name="hello_world">Hello World!</string>
</resources>

We have learned how to create a floating contextual menu as well as a contextual menu in action mode. The full project code can be found at https://github.com/dmitrilc/DaniwebAndroidContextualMenus.

Among all of the Android libraries, Paging 3 is perhaps one of the hardest to understand.

Personally, I think the problem with Paging 3 are:

1. Developers need to learn a lot of custom classes before they can understand how Paging 3 works under the hood and how to use the library to its fullest potential. The list of classes is long. It includes:

    CombinedLoadStates
    ConcatAdapter
    DiffUtil
    LoadState
    LoadStateAdapter
    LoadStates
    LoadType
    Pager
    PagingConfig
    PagingData
    PagingDataAdapter
    PagingSource
    PagingSource.LoadResult
    PagingState
    RemoteMediator
    RemoteMediator.MediatorResult

2. You will have to dig deep into Pager/PagingDataAdapter source code to understand how PagingSource and PagingData are invalidated. Because you are not in control of creating PagingData yourself, how the PagingSource/PagingData pair is created and invalidated can be too magical for comfort.

3. Unlike other libraries that only provide functionality for a specific layer, Paging 3 library classes span across multiple layers of your App: UI, ViewModel, Repository, Database.

On the bright side The final result is not a lot of code, and using this pre-made library would still most likely be simpler than rolling your own.

Paging 3 can operate in two different modes. The first mode only displays paged data from a network without an offline database as a cache. In the second mode, you can enlist a local Room database to use as your cache, for offline support.

In this tutorial, we will learn how to use Paging 3 without an offline database.

At the end of the tutorial, you would have learned:

1. How to use PagingSource to display data from the network.

1. Android Studio. The version used in this tutorial is Bumblebee 2021.1.1 Patch 3.

1. Intermediate Android.
2. MVVM.
3. Hilt.
4. Kotlin Flow.
5. Retrofit.
6. Moshi.
7. ViewBinding.
8. DataBinding.

To follow along with the tutorial, perform the steps below:

1. Clone the sample app called CatFacts from https://github.com/dmitrilc/CatFacts.git
2. Switch to the No_RemoteMediator branch.

The project is already completed, but we will walk through the built app to learn what happens at each step.

In the screenshot of the project structure below, we are only concerned about the classes in green. It is okay to ignore the packages and classes in red because they are not really interesting to the current topic; they are just Hilt and Retrofit classes if you are curious.

You can run the app now. It is just a RecyclerView that displays cat facts received from the Cat Facts API. As you reach the end of the list, it will reach out to the network to get more data. You can also verify this behavior by using the Network Inspector. Refer to the animation below as a reference.

The App also has a button to trigger a refresh, which causes Pager to reload data at a specified location.

To understand the apps architecture, we can refer to the diagram below.

In the diagram above, how PagingDataAdapter loads another item is mostly hidden from us, so we can just call it implementation details. Because implementation details are subject to change, It is really not worth it to divulge them in this tutorial. Though if you are still confused and wants to know what happens, you can start with debugging backwards at the beginning of the CatFactPagingSource#load() function.

The classes PagingDataAdapter, MainActivity, CatFactsViewModel, CatFactRepo, Pager, and WebService all exist within the project code. This is what the app does:

1. At first launch, the Repository prefetches enough data to display on the screen. It might load one or two pages, depending on the height of the screen and how many facts can fit.

2. As the user scrolls to the bottom of the RecyclerView, PagingDataAdapter signals the Pager to load more items, invalidating the current generation (PagingSource/PagingData pair) as well as generating a new generation.

3. After the new pair of PagingSource/PagingData is generated, a new PagingData object is pushed to the PagingDataAdapter.

4. At the top of the App, there is a Button to to manually trigger a refresh() action. This app always start from the beginning because I am trying to avoid business logic overload in this tutorial, which can lead to unnecessary complexity. Just keep in mind that this refresh feature is very situational and not all Apps will need it, but we are still required to override it.

5. I have also injected a callback into CatFactPagingSource, which can be used to update the UI of the last loaded page. This is just to confirm that the refresh is working correctly. This step is entirely optional.

When using Paging 3 without an offline database, you must first define a custom implementation of PagingSource yourself. The only two functions that you need to override are load() and getRefreshKey().

In CatFactPagingSource.kt, our implementation of load() is as below.

override suspend fun load(params: LoadParams<Int>): LoadResult<Int, CatFact> {
   try {
       // Start refresh at page 1 if undefined.
       val position = params.key ?: CAT_FACTS_STARTING_PAGE_INDEX
       pageNumberUpdater(position)

       val response = webService.getCatFactPage(position)
       val catFacts = response.data

       val prevKey = if (position == CAT_FACTS_STARTING_PAGE_INDEX) {
           null //if current position is the same as the starting position
       } else {
           position - 1
       }

       val nextKey = if (catFacts.isEmpty()){
           null //if there is no more data to load in the current direction
       } else {
           position + 1
       }

       return LoadResult.Page(
           data = catFacts,
           prevKey = prevKey,
           nextKey = nextKey
       )
   } catch (exception: IOException) {
       return LoadResult.Error(exception)
   } catch (exception: HttpException) {
       return LoadResult.Error(exception)
   }
}

Let us go through this code line by line.

1. The function load() has a parameter of type LoadParams. An internal implementation will provide the argument when it calls load(). The most important properties of LoadParams would be its public properties key and loadSize.

2. Typically, the key usually come from 4 different places:
   A. The previous or the next key that you have provided to the previous generation, depending on the LoadType (APPEND or PREPEND).
   B. The key from the getRefreshKey() function.
   C. The initialKey property when constructing the Pager.
   D. A custom key defined by you. For example, in this App, we used the constant CAT_FACTS_STARTING_PAGE_INDEX as the initial key.

3. The other property of LoadParams, loadSize indicates how many items to load. This is the number pageSize passed to the PagingConfig in the CatFactRepo.kt file. The load() function is not required to use this property if it does want to.

4. You are in control of how you want to calculate the previous and next keys. This heavily depends on the remote API that you are fetching from. For this App, we simply add or subtract one to the current key depending on the scrolling direction.

5. Lastly, we must return a LoadResult object, which can be a LoadResult.Page on success or LoadResult.Error/LoadResult.Invalid if something went wrong. All three classes Page, Error, and Invaliad are subclasses of LoadResult.

Next, we will have to override getRefreshKey() as well. Our current implementation is as below.

override fun getRefreshKey(state: PagingState<Int, CatFact>): Int? {
   /*
   This will always start loading from the beginning.
   Same effect as return AT_FACTS_STARTING_PAGE_INDEX.
   */
   return null
   //If you want the list to resume at page 5, return 5, etc..
}

We are simply returning null, which the load() function will receive and then resets the key back into CAT_FACTS_STARTING_PAGE_INDEX, which will starts loading page one or page two as well, depending on whether the loaded items can fill the viewport.

To connect the UI and the Data layers, we would need to use a Pager object. The code below illustrates how to create a Pager.

fun getCatFactPagerWithoutRemoteMediator(): Flow<PagingData<CatFact>> =
   Pager(
       config = PagingConfig(pageSize = 1)
   ) {
       CatFactPagingSource(webService){ page ->
           _currentPage.value = "$page"
       }
   }
       .flow

After creation, its only public property is flow, which can be collected in other layers. There exists an extension function that exposes this flow as a LiveData as well.

To consume the Flow<PagingData<T>>, we must use a special RecycleView Adapter called PagingDataAdapter.

class PagingCatFactAdapter : PagingDataAdapter<CatFact, PagingCatFactAdapter.CatFactViewHolder>(DiffCallback) {

   class CatFactViewHolder(val binding: CatFactBinding) : RecyclerView.ViewHolder(binding.root){}

   override fun onCreateViewHolder(parent: ViewGroup, viewType: Int) =
       CatFactViewHolder(
           CatFactBinding.inflate(
               LayoutInflater.from(parent.context),
               parent,
               false
           )
       )

   //Binds data to a viewholder
   override fun onBindViewHolder(holder: CatFactViewHolder, position: Int) {
       val item = getItem(position)
       if (item != null) {
           holder.binding.catFact.text = item.fact
       }
   }

   object DiffCallback : DiffUtil.ItemCallback<CatFact>() {
       override fun areItemsTheSame(old: CatFact, new: CatFact) = old == new
       override fun areContentsTheSame(old: CatFact, new: CatFact) = old.fact == new.fact
   }

}

The implementation is very similar to a normal adapter, there are only 3 main differences.

1. You must subclass PagingDataAdapter.
2. PagingDataAdapter requires a DiffUtil.ItemCallback in its constructor, which you must implement as well. Your implementation of DiffUtil.ItemCallback must know how to compare the objects and its contents.
3. You do not have to implement getItemCount() yourself.

Lastly, we must collect the Flow from the Pager, and then submit it to PagingDataAdapter in the Activity or Fragment.

lifecycleScope.launch {
   viewModel.pagerNoRemoteMediator.collectLatest {
       adapter.submitData(it)
   }
}

Now that we have understood everything, it is time to run the App again to see how the refresh functionality works.

Congratulations! We have learned how to use Paging 3 without offline support in this tutorial. If you are interested in learning how to use Paging 3 with offline support as well, check out the RemoteMediator tutorial here. The full project code can be found at https://github.com/dmitrilc/CatFacts/tree/No_RemoteMediator

I am contemplating writing a speech-controlled music player app for android. I am experienced in writing PC applications, and wrote a rather sharp speech controlled MP3 player using VB in the 1990s. I have also used c, c++, and several other languages in the past, but I have zero experience with mobile app development.

My priorities are a fast, memory-efficient app with good command-&-control and dictation abilities (iPhone compatibility would be a plus, but I'm willing to write a separate app for iPhone if the android app goes well).

What language/framework would you recommend?

In this tutorial, we will learn how to apply Material 3 colors and Dynamic Colors to our App.

At the end of the tutorial, you would have learned:

1. How to apply Material 3 colors.
2. How to enable Dynamic Colors.

1. Android Studio. The version used in this tutorial is Bumblebee 2021.1.1 Patch 3.

1. Basic Android.

To follow along with the tutorial, perform the steps below:

1. Create a new Android project with the default Empty Activity.

2. Remove the default TextView.

3. Copy and paste the code below into activity_main.xml. This will add a couple of random widgets mainly for us to see the visual effects. The code inside is not really important.

    <?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"
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:text="Button"
           app:layout_constraintBottom_toTopOf="@+id/switch1"
           app:layout_constraintEnd_toEndOf="parent"
           app:layout_constraintHorizontal_bias="0.5"
           app:layout_constraintStart_toStartOf="parent"
           app:layout_constraintTop_toTopOf="parent" />
   
       <androidx.appcompat.widget.SwitchCompat
           android:id="@+id/switch1"
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:text="Switch"
           app:layout_constraintBottom_toTopOf="@+id/radioGroup"
           app:layout_constraintEnd_toEndOf="parent"
           app:layout_constraintHorizontal_bias="0.5"
           app:layout_constraintStart_toStartOf="parent"
           app:layout_constraintTop_toBottomOf="@+id/button" />
   
       <RadioGroup
           android:id="@+id/radioGroup"
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           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/switch1">
   
           <RadioButton
               android:id="@+id/radioButton"
               android:layout_width="match_parent"
               android:layout_height="wrap_content"
               android:text="RadioButton" />
   
           <RadioButton
               android:id="@+id/radioButton2"
               android:layout_width="match_parent"
               android:layout_height="wrap_content"
               android:text="RadioButton" />
   
       </RadioGroup>
    </androidx.constraintlayout.widget.ConstraintLayout>

4. Inside of the Module build.gradle, change the version of com.google.android.material:material to 1.6.0-rc01.

When the project was first created, Android Studio automatically chose the Theme.MaterialComponents.DayNight.DarkActionBar theme for us. Themes starting with Theme.MaterialComponents.* actually belongs to Material 2, so in order to use a Material 3 theme, we must inherit from a Theme.Material3.* theme instead.

Fortunately, there is a web tool called Material 3 Theme Builder that will generate the code for us, so changing the theme is as simple as copying and pasting. Follow the steps below to generate our own Material 3 theme.

1. Follow the link https://material-foundation.github.io/material-theme-builder/#/custom and navigate to the Custom tab, if not already selected. You can ignore the Dynamic tab for now.

2. On the color generator, you are really only required to choose your own primary color. After selecting the primary color, the tool will automatically update your secondary and tertiary colors.
   

3. For this tutorial, select rgb(255, 0, 128) (#ff0080) as the primary color and leave everything else as default.

4. At the top left corner, select Export -> as Android Views (XML).
   

5. Extract the downloaded material-theme.zip file. You will then 2 folders, values and values-night.

6. Replace entire <resource> block in your projects colors.xml with the the content of colors.xml in the downloaded values folder.

7. Your new colors.xml file should look like the code below.

    <?xml version="1.0" encoding="utf-8"?>
    <resources>
       <color name="md_theme_light_primary">#BB005A</color>
       <color name="md_theme_light_onPrimary">#FFFFFF</color>
       <color name="md_theme_light_primaryContainer">#FFD9E2</color>
       <color name="md_theme_light_onPrimaryContainer">#3F001A</color>
       <color name="md_theme_light_secondary">#74565D</color>
       <color name="md_theme_light_onSecondary">#FFFFFF</color>
       <color name="md_theme_light_secondaryContainer">#FFD9E1</color>
       <color name="md_theme_light_onSecondaryContainer">#2B151B</color>
       <color name="md_theme_light_tertiary">#7B5734</color>
       <color name="md_theme_light_onTertiary">#FFFFFF</color>
       <color name="md_theme_light_tertiaryContainer">#FFDCBD</color>
       <color name="md_theme_light_onTertiaryContainer">#2D1600</color>
       <color name="md_theme_light_error">#BA1B1B</color>
       <color name="md_theme_light_errorContainer">#FFDAD4</color>
       <color name="md_theme_light_onError">#FFFFFF</color>
       <color name="md_theme_light_onErrorContainer">#410001</color>
       <color name="md_theme_light_background">#FCFCFC</color>
       <color name="md_theme_light_onBackground">#201A1B</color>
       <color name="md_theme_light_surface">#FCFCFC</color>
       <color name="md_theme_light_onSurface">#201A1B</color>
       <color name="md_theme_light_surfaceVariant">#F3DEE1</color>
       <color name="md_theme_light_onSurfaceVariant">#514346</color>
       <color name="md_theme_light_outline">#837376</color>
       <color name="md_theme_light_inverseOnSurface">#FAEEEF</color>
       <color name="md_theme_light_inverseSurface">#352F30</color>
       <color name="md_theme_light_inversePrimary">#FFB0C6</color>
       <color name="md_theme_light_shadow">#000000</color>
       <color name="md_theme_light_primaryInverse">#FFB0C6</color>
       <color name="md_theme_dark_primary">#FFB0C6</color>
       <color name="md_theme_dark_onPrimary">#65002D</color>
       <color name="md_theme_dark_primaryContainer">#8F0043</color>
       <color name="md_theme_dark_onPrimaryContainer">#FFD9E2</color>
       <color name="md_theme_dark_secondary">#E3BDC5</color>
       <color name="md_theme_dark_onSecondary">#432930</color>
       <color name="md_theme_dark_secondaryContainer">#5B3F46</color>
       <color name="md_theme_dark_onSecondaryContainer">#FFD9E1</color>
       <color name="md_theme_dark_tertiary">#EEBD92</color>
       <color name="md_theme_dark_onTertiary">#472A0A</color>
       <color name="md_theme_dark_tertiaryContainer">#61401F</color>
       <color name="md_theme_dark_onTertiaryContainer">#FFDCBD</color>
       <color name="md_theme_dark_error">#FFB4A9</color>
       <color name="md_theme_dark_errorContainer">#930006</color>
       <color name="md_theme_dark_onError">#680003</color>
       <color name="md_theme_dark_onErrorContainer">#FFDAD4</color>
       <color name="md_theme_dark_background">#201A1B</color>
       <color name="md_theme_dark_onBackground">#ECE0E1</color>
       <color name="md_theme_dark_surface">#201A1B</color>
       <color name="md_theme_dark_onSurface">#ECE0E1</color>
       <color name="md_theme_dark_surfaceVariant">#514346</color>
       <color name="md_theme_dark_onSurfaceVariant">#D6C2C5</color>
       <color name="md_theme_dark_outline">#9E8D90</color>
       <color name="md_theme_dark_inverseOnSurface">#201A1B</color>
       <color name="md_theme_dark_inverseSurface">#ECE0E1</color>
       <color name="md_theme_dark_inversePrimary">#BB005A</color>
       <color name="md_theme_dark_shadow">#000000</color>
       <color name="md_theme_dark_primaryInverse">#BB005A</color>
    </resources>

8. Similarly, your project files themes.xml and themes.xml (night) should be updated as well with the two themes.xml files in the downloaded zip file. When you are copying and pasting these files over, make sure to preserve your own apps theme name and change the parent to Theme.Material3.DayNight since this matches our current theme. Theme.MaterialComponents.DayNight.DarkActionBar is not available in Material 3, so the closest thing would be Theme.Material3.DayNight.

9. Your themes.xml should look similar to the code below.

    <resources>
       <style name="Theme.DaniwebAndroidNativeMaterial3Colors" parent="Theme.Material3.DayNight">
           <item name="colorPrimary">@color/md_theme_light_primary</item>
           <item name="colorOnPrimary">@color/md_theme_light_onPrimary</item>
           <item name="colorPrimaryContainer">@color/md_theme_light_primaryContainer</item>
           <item name="colorOnPrimaryContainer">@color/md_theme_light_onPrimaryContainer</item>
           <item name="colorSecondary">@color/md_theme_light_secondary</item>
           <item name="colorOnSecondary">@color/md_theme_light_onSecondary</item>
           <item name="colorSecondaryContainer">@color/md_theme_light_secondaryContainer</item>
           <item name="colorOnSecondaryContainer">@color/md_theme_light_onSecondaryContainer</item>
           <item name="colorTertiary">@color/md_theme_light_tertiary</item>
           <item name="colorOnTertiary">@color/md_theme_light_onTertiary</item>
           <item name="colorTertiaryContainer">@color/md_theme_light_tertiaryContainer</item>
           <item name="colorOnTertiaryContainer">@color/md_theme_light_onTertiaryContainer</item>
           <item name="colorError">@color/md_theme_light_error</item>
           <item name="colorErrorContainer">@color/md_theme_light_errorContainer</item>
           <item name="colorOnError">@color/md_theme_light_onError</item>
           <item name="colorOnErrorContainer">@color/md_theme_light_onErrorContainer</item>
           <item name="android:colorBackground">@color/md_theme_light_background</item>
           <item name="colorOnBackground">@color/md_theme_light_onBackground</item>
           <item name="colorSurface">@color/md_theme_light_surface</item>
           <item name="colorOnSurface">@color/md_theme_light_onSurface</item>
           <item name="colorSurfaceVariant">@color/md_theme_light_surfaceVariant</item>
           <item name="colorOnSurfaceVariant">@color/md_theme_light_onSurfaceVariant</item>
           <item name="colorOutline">@color/md_theme_light_outline</item>
           <item name="colorOnSurfaceInverse">@color/md_theme_light_inverseOnSurface</item>
           <item name="colorSurfaceInverse">@color/md_theme_light_inverseSurface</item>
    <!--        <item name="colorInversePrimary">@color/md_theme_light_inversePrimary</item>
           <item name="colorShadow">@color/md_theme_light_shadow</item>-->
           <item name="colorPrimaryInverse">@color/md_theme_light_primaryInverse</item>
       </style>
    </resources>

10. Your themes.xml (night) should look similar to the code below.

     <resources>
        <style name="Theme.DaniwebAndroidNativeMaterial3Colors" parent="Theme.Material3.DayNight">
            <item name="colorPrimary">@color/md_theme_dark_primary</item>
            <item name="colorOnPrimary">@color/md_theme_dark_onPrimary</item>
            <item name="colorPrimaryContainer">@color/md_theme_dark_primaryContainer</item>
            <item name="colorOnPrimaryContainer">@color/md_theme_dark_onPrimaryContainer</item>
            <item name="colorSecondary">@color/md_theme_dark_secondary</item>
            <item name="colorOnSecondary">@color/md_theme_dark_onSecondary</item>
            <item name="colorSecondaryContainer">@color/md_theme_dark_secondaryContainer</item>
            <item name="colorOnSecondaryContainer">@color/md_theme_dark_onSecondaryContainer</item>
            <item name="colorTertiary">@color/md_theme_dark_tertiary</item>
            <item name="colorOnTertiary">@color/md_theme_dark_onTertiary</item>
            <item name="colorTertiaryContainer">@color/md_theme_dark_tertiaryContainer</item>
            <item name="colorOnTertiaryContainer">@color/md_theme_dark_onTertiaryContainer</item>
            <item name="colorError">@color/md_theme_dark_error</item>
            <item name="colorErrorContainer">@color/md_theme_dark_errorContainer</item>
            <item name="colorOnError">@color/md_theme_dark_onError</item>
            <item name="colorOnErrorContainer">@color/md_theme_dark_onErrorContainer</item>
            <item name="android:colorBackground">@color/md_theme_dark_background</item>
            <item name="colorOnBackground">@color/md_theme_dark_onBackground</item>
            <item name="colorSurface">@color/md_theme_dark_surface</item>
            <item name="colorOnSurface">@color/md_theme_dark_onSurface</item>
            <item name="colorSurfaceVariant">@color/md_theme_dark_surfaceVariant</item>
            <item name="colorOnSurfaceVariant">@color/md_theme_dark_onSurfaceVariant</item>
            <item name="colorOutline">@color/md_theme_dark_outline</item>
            <item name="colorOnSurfaceInverse">@color/md_theme_dark_inverseOnSurface</item>
            <item name="colorSurfaceInverse">@color/md_theme_dark_inverseSurface</item>
     <!--        <item name="colorInversePrimary">@color/md_theme_dark_inversePrimary</item>
            <item name="colorShadow">@color/md_theme_dark_shadow</item>-->
            <item name="colorPrimaryInverse">@color/md_theme_dark_primaryInverse</item>
        </style>
     </resources>

11. Notice that we have commented out colorInversePrimary and colorShadow. They are generated by the Theme Builder, but they cause compile errors in our code. These color roles are not listed in the official docs. Since the Theme Builder is a closed source project and I did not find any obvious error reports, I am going to assume that it is safe to comment them out for now.

Before Material 3 was applied, our app looks like this

After applying Material 3, our app looks like this

The main differences are that the Button takes on a more rounded shape and the primary color is a dark pinkish color as opposed to the bright blue previously.

Material 3 also introduced the Dynamic Color feature, which lets your app change color based on the users current wallpaper. Enabling it on top of the existing Material 3 theme is super easy. Follow the steps below:

1. Create a new class called MyApplication that extends Application.

2. Override its onCreate() function to apply Dynamic Colors to the entire app with the code below.

    class MyApplication : Application() {
   
       override fun onCreate() {
           super.onCreate()
           DynamicColors.applyToActivitiesIfAvailable(this)
       }
   
    }

3. Add the android:name attribute to the <application> element in the manifest file.

    android:name=".MyApplication" 

If you start our app now, then you will see it using a different theme compared to before because the theme changes dynamically based on the current background wallpaper. Reference the pictures below to see the wallpaper/app theme pairs.

MyApplication.kt

    class MyApplication : Application() {

       override fun onCreate() {
           super.onCreate()
           DynamicColors.applyToActivitiesIfAvailable(this)
       }

    }

AndroidManifest.xml

    <?xml version="1.0" encoding="utf-8"?>
    <manifest xmlns:android="http://schemas.android.com/apk/res/android"
       package="com.example.daniwebandroidnativematerial3colors">

       <application
           android:name=".MyApplication"
           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.DaniwebAndroidNativeMaterial3Colors">
           <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>

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"
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:text="Button"
           app:layout_constraintBottom_toTopOf="@+id/switch1"
           app:layout_constraintEnd_toEndOf="parent"
           app:layout_constraintHorizontal_bias="0.5"
           app:layout_constraintStart_toStartOf="parent"
           app:layout_constraintTop_toTopOf="parent" />

       <androidx.appcompat.widget.SwitchCompat
           android:id="@+id/switch1"
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:text="Switch"
           app:layout_constraintBottom_toTopOf="@+id/radioGroup"
           app:layout_constraintEnd_toEndOf="parent"
           app:layout_constraintHorizontal_bias="0.5"
           app:layout_constraintStart_toStartOf="parent"
           app:layout_constraintTop_toBottomOf="@+id/button" />

       <RadioGroup
           android:id="@+id/radioGroup"
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           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/switch1">

           <RadioButton
               android:id="@+id/radioButton"
               android:layout_width="match_parent"
               android:layout_height="wrap_content"
               android:text="RadioButton" />

           <RadioButton
               android:id="@+id/radioButton2"
               android:layout_width="match_parent"
               android:layout_height="wrap_content"
               android:text="RadioButton" />

       </RadioGroup>
    </androidx.constraintlayout.widget.ConstraintLayout>

colors.xml

    <?xml version="1.0" encoding="utf-8"?>
    <resources>
       <color name="md_theme_light_primary">#BB005A</color>
       <color name="md_theme_light_onPrimary">#FFFFFF</color>
       <color name="md_theme_light_primaryContainer">#FFD9E2</color>
       <color name="md_theme_light_onPrimaryContainer">#3F001A</color>
       <color name="md_theme_light_secondary">#74565D</color>
       <color name="md_theme_light_onSecondary">#FFFFFF</color>
       <color name="md_theme_light_secondaryContainer">#FFD9E1</color>
       <color name="md_theme_light_onSecondaryContainer">#2B151B</color>
       <color name="md_theme_light_tertiary">#7B5734</color>
       <color name="md_theme_light_onTertiary">#FFFFFF</color>
       <color name="md_theme_light_tertiaryContainer">#FFDCBD</color>
       <color name="md_theme_light_onTertiaryContainer">#2D1600</color>
       <color name="md_theme_light_error">#BA1B1B</color>
       <color name="md_theme_light_errorContainer">#FFDAD4</color>
       <color name="md_theme_light_onError">#FFFFFF</color>
       <color name="md_theme_light_onErrorContainer">#410001</color>
       <color name="md_theme_light_background">#FCFCFC</color>
       <color name="md_theme_light_onBackground">#201A1B</color>
       <color name="md_theme_light_surface">#FCFCFC</color>
       <color name="md_theme_light_onSurface">#201A1B</color>
       <color name="md_theme_light_surfaceVariant">#F3DEE1</color>
       <color name="md_theme_light_onSurfaceVariant">#514346</color>
       <color name="md_theme_light_outline">#837376</color>
       <color name="md_theme_light_inverseOnSurface">#FAEEEF</color>
       <color name="md_theme_light_inverseSurface">#352F30</color>
       <color name="md_theme_light_inversePrimary">#FFB0C6</color>
       <color name="md_theme_light_shadow">#000000</color>
       <color name="md_theme_light_primaryInverse">#FFB0C6</color>
       <color name="md_theme_dark_primary">#FFB0C6</color>
       <color name="md_theme_dark_onPrimary">#65002D</color>
       <color name="md_theme_dark_primaryContainer">#8F0043</color>
       <color name="md_theme_dark_onPrimaryContainer">#FFD9E2</color>
       <color name="md_theme_dark_secondary">#E3BDC5</color>
       <color name="md_theme_dark_onSecondary">#432930</color>
       <color name="md_theme_dark_secondaryContainer">#5B3F46</color>
       <color name="md_theme_dark_onSecondaryContainer">#FFD9E1</color>
       <color name="md_theme_dark_tertiary">#EEBD92</color>
       <color name="md_theme_dark_onTertiary">#472A0A</color>
       <color name="md_theme_dark_tertiaryContainer">#61401F</color>
       <color name="md_theme_dark_onTertiaryContainer">#FFDCBD</color>
       <color name="md_theme_dark_error">#FFB4A9</color>
       <color name="md_theme_dark_errorContainer">#930006</color>
       <color name="md_theme_dark_onError">#680003</color>
       <color name="md_theme_dark_onErrorContainer">#FFDAD4</color>
       <color name="md_theme_dark_background">#201A1B</color>
       <color name="md_theme_dark_onBackground">#ECE0E1</color>
       <color name="md_theme_dark_surface">#201A1B</color>
       <color name="md_theme_dark_onSurface">#ECE0E1</color>
       <color name="md_theme_dark_surfaceVariant">#514346</color>
       <color name="md_theme_dark_onSurfaceVariant">#D6C2C5</color>
       <color name="md_theme_dark_outline">#9E8D90</color>
       <color name="md_theme_dark_inverseOnSurface">#201A1B</color>
       <color name="md_theme_dark_inverseSurface">#ECE0E1</color>
       <color name="md_theme_dark_inversePrimary">#BB005A</color>
       <color name="md_theme_dark_shadow">#000000</color>
       <color name="md_theme_dark_primaryInverse">#BB005A</color>
    </resources>

themes.xml

    <resources>
       <style name="Theme.DaniwebAndroidNativeMaterial3Colors" parent="Theme.Material3.DayNight">
           <item name="colorPrimary">@color/md_theme_light_primary</item>
           <item name="colorOnPrimary">@color/md_theme_light_onPrimary</item>
           <item name="colorPrimaryContainer">@color/md_theme_light_primaryContainer</item>
           <item name="colorOnPrimaryContainer">@color/md_theme_light_onPrimaryContainer</item>
           <item name="colorSecondary">@color/md_theme_light_secondary</item>
           <item name="colorOnSecondary">@color/md_theme_light_onSecondary</item>
           <item name="colorSecondaryContainer">@color/md_theme_light_secondaryContainer</item>
           <item name="colorOnSecondaryContainer">@color/md_theme_light_onSecondaryContainer</item>
           <item name="colorTertiary">@color/md_theme_light_tertiary</item>
           <item name="colorOnTertiary">@color/md_theme_light_onTertiary</item>
           <item name="colorTertiaryContainer">@color/md_theme_light_tertiaryContainer</item>
           <item name="colorOnTertiaryContainer">@color/md_theme_light_onTertiaryContainer</item>
           <item name="colorError">@color/md_theme_light_error</item>
           <item name="colorErrorContainer">@color/md_theme_light_errorContainer</item>
           <item name="colorOnError">@color/md_theme_light_onError</item>
           <item name="colorOnErrorContainer">@color/md_theme_light_onErrorContainer</item>
           <item name="android:colorBackground">@color/md_theme_light_background</item>
           <item name="colorOnBackground">@color/md_theme_light_onBackground</item>
           <item name="colorSurface">@color/md_theme_light_surface</item>
           <item name="colorOnSurface">@color/md_theme_light_onSurface</item>
           <item name="colorSurfaceVariant">@color/md_theme_light_surfaceVariant</item>
           <item name="colorOnSurfaceVariant">@color/md_theme_light_onSurfaceVariant</item>
           <item name="colorOutline">@color/md_theme_light_outline</item>
           <item name="colorOnSurfaceInverse">@color/md_theme_light_inverseOnSurface</item>
           <item name="colorSurfaceInverse">@color/md_theme_light_inverseSurface</item>
           <!--        <item name="colorInversePrimary">@color/md_theme_light_inversePrimary</item>
                   <item name="colorShadow">@color/md_theme_light_shadow</item>-->
           <item name="colorPrimaryInverse">@color/md_theme_light_primaryInverse</item>
       </style>
    </resources>

themes.xml (night)

    <resources>
       <style name="Theme.DaniwebAndroidNativeMaterial3Colors" parent="Theme.Material3.DayNight">
           <item name="colorPrimary">@color/md_theme_dark_primary</item>
           <item name="colorOnPrimary">@color/md_theme_dark_onPrimary</item>
           <item name="colorPrimaryContainer">@color/md_theme_dark_primaryContainer</item>
           <item name="colorOnPrimaryContainer">@color/md_theme_dark_onPrimaryContainer</item>
           <item name="colorSecondary">@color/md_theme_dark_secondary</item>
           <item name="colorOnSecondary">@color/md_theme_dark_onSecondary</item>
           <item name="colorSecondaryContainer">@color/md_theme_dark_secondaryContainer</item>
           <item name="colorOnSecondaryContainer">@color/md_theme_dark_onSecondaryContainer</item>
           <item name="colorTertiary">@color/md_theme_dark_tertiary</item>
           <item name="colorOnTertiary">@color/md_theme_dark_onTertiary</item>
           <item name="colorTertiaryContainer">@color/md_theme_dark_tertiaryContainer</item>
           <item name="colorOnTertiaryContainer">@color/md_theme_dark_onTertiaryContainer</item>
           <item name="colorError">@color/md_theme_dark_error</item>
           <item name="colorErrorContainer">@color/md_theme_dark_errorContainer</item>
           <item name="colorOnError">@color/md_theme_dark_onError</item>
           <item name="colorOnErrorContainer">@color/md_theme_dark_onErrorContainer</item>
           <item name="android:colorBackground">@color/md_theme_dark_background</item>
           <item name="colorOnBackground">@color/md_theme_dark_onBackground</item>
           <item name="colorSurface">@color/md_theme_dark_surface</item>
           <item name="colorOnSurface">@color/md_theme_dark_onSurface</item>
           <item name="colorSurfaceVariant">@color/md_theme_dark_surfaceVariant</item>
           <item name="colorOnSurfaceVariant">@color/md_theme_dark_onSurfaceVariant</item>
           <item name="colorOutline">@color/md_theme_dark_outline</item>
           <item name="colorOnSurfaceInverse">@color/md_theme_dark_inverseOnSurface</item>
           <item name="colorSurfaceInverse">@color/md_theme_dark_inverseSurface</item>
    <!--        <item name="colorInversePrimary">@color/md_theme_dark_inversePrimary</item>
           <item name="colorShadow">@color/md_theme_dark_shadow</item>-->
           <item name="colorPrimaryInverse">@color/md_theme_dark_primaryInverse</item>
       </style>
    </resources>

Module build.gradle

    plugins {
       id 'com.android.application'
       id 'org.jetbrains.kotlin.android'
    }

    android {
       compileSdk 32

       defaultConfig {
           applicationId "com.example.daniwebandroidnativematerial3colors"
           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:1.6.0-rc01'
       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'
    }

Congratulations! You have learned how to add Material 3 colors into an Android app as well as how to add Dynamic Colors. The full project code can be found at https://github.com/dmitrilc/DaniwebAndroidNativeMaterial3Colors

Hey guys, I am trying to upload text entered by a user of my app in an edit text to a google firebase application. Tried to find some reference online on how to do this, the article suggested I add Firebase.FirebaseDatabae.net which I added to the project via the Nuget package manager. I logged into my Google Firebase Console and got the Firebase url string for use with the client. I instantiated the client like below

protected string firebase_link = "https://xxxxxx-default-rtdb.firebaseio.com/";
FirebaseClient myclient;

//create a new instance of the firebase client
protected override void OnCreate(Bundle savedInstanceState){
 myclient = new FirebaseClient(firebase_link);
//define the buton for uploading the details in the edit text to the server
Button upload = FindViewById<Button>(Resource.Id.upload);
//subscribe to the event listener
upload.Click+=Upload_Click;
}
//method to upload text to the firebase app
private void Upload_Click(object sender, EventArgs e){
               try {
                if(myclient.Child("Users").PostAsync("Timothy").IsCompleted){
                    Snackbar.Make(email, "Firebase call completed succesfully", Snackbar.LengthLong).Show();
                }
                else
                {
                    Snackbar.Make(email, "An exception ocurred, try again in a little bit", Snackbar.LengthLong).Show();
                }
            }
            catch (Exception j)
            {
                Toast.MakeText(this,j.Message, ToastLength.Long).Show();    
            }
}

When I run the app, it is not making changes to the firebase database online, neither is it throwing an exception, it is just returning false for the if conditional structure inside the try catch block, please help.