Guide to integrate Firebase Cloud Messaging (FCM) in Android

plugins { id("com.android.application") version "7.3.0" apply false // ... 
**// Add the dependency for the Google services Gradle plugin**
id("com.google.gms.google-services") version "4.4.0" apply false
}

plugins { id("com.android.application") 
 **// Add the Google services Gradle**
 plugin id("com.google.gms.google-services")
}

dependencies 
{ 
**// Import the Firebase BoM implementation(platform("com.google.firebase:firebase-bom:32.7.1"))** // When using the BoM, you don't specify versions in Firebase library dependencies 
**// Add the dependency for the Firebase SDK for Firebase Cloud Messaging(FCM)** 
implementation("com.google.firebase:firebase-messaging")
**// TODO: Add the dependencies for Firebase products you want to use** // See https://firebase.google.com/docs/android/setup#available-libraries 
//For example, add the dependencies for Firebase Authentication and Cloud Firestore 
implementation("com.google.firebase:firebase-auth") implementation("com.google.firebase:firebase-firestore") 
}

<service 
 android:name=".fcm.MyFirebaseMessagingService" 
 android:exported="false"> 
<intent-filter>
<action android:name="com.google.firebase.MESSAGING_EVENT" /> 
</intent-filter>
</service>

<!-- Set custom default icon. This is used when no icon is set for incoming notification messages. -->  
<meta-data  android:name="com.google.firebase.messaging.default_notification_icon"
android:resource="@drawable/ic_stat_ic_notification"  />  
<!-- Set color used with incoming notification messages. This is used when no color is set for the incoming  
    notification message. -->  
<meta-data  android:name="com.google.firebase.messaging.default_notification_color"
android:resource="@color/colorAccent"  />

<!-- From Android 8.0 (API level 26) and higher, [notification channels](https://developer.android.com/guide/topics/ui/notifiers/notifications.html#ManageChannels) are supported and recommended.
FCM provides a default notification channel with basic settings.
If you prefer to [create](https://developer.android.com/guide/topics/ui/notifiers/notifications.html#CreateChannel) and use your own default channel, set `default_notification_channel_id` to the ID of your notification channel object as shown. -->
<meta-data  android:name="com.google.firebase.messaging.default_notification_channel_id"  
android:value="@string/default_notification_channel_id"  />

// Declare the launcher at the top of your Activity/Fragment: 
private val requestPermissionLauncher = registerForActivityResult( ActivityResultContracts.RequestPermission(),)
{ isGranted: Boolean -> if (isGranted) 
{ 
// FCM SDK (and your app) can post notifications. 
} 
else 
{ // TODO: Inform user that that your app will not show notifications. 
} 
} 

private fun askNotificationPermission() {
 // This is only necessary for API level >= 33 (TIRAMISU) 
 if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) 
 { 
 if (ContextCompat.checkSelfPermission(this, Manifest.permission.POST_NOTIFICATIONS) == PackageManager.PERMISSION_GRANTED ) 
 { 
 // FCM SDK (and your app) can post notifications. 
 } 
 else if (shouldShowRequestPermissionRationale(Manifest.permission.POST_NOTIFICATIONS)) 
 { // TODO: display an educational UI explaining to the user the features that will be enabled 
 //   by them granting the POST_NOTIFICATION permission. This UI should provide the user 
 //   "OK" and "No thanks" buttons. If the user selects "OK," directly request the permission. 
 //   If the user selects "No thanks," allow the user to continue without notifications. 
 } else 
 { 
 // Directly ask for the permission requestPermissionLauncher.launch(Manifest.permission.POST_NOTIFICATIONS) 
 } 
 } 
}

Firebase.messaging.token.addOnCompleteListener(  
   OnCompleteListener { task ->  
 if (!task.isSuccessful) {  
           Log.w(TAG, "Fetching FCM registration token failed", task.exception)  
           return@OnCompleteListener  
 }  
 
 // Get new FCM registration token  
 val token = task.result  
 
 // Log and toast  
 val msg = getString(R.string.msg_token_fmt, token)  
       Log.d(TAG, msg)  
 
  //Implement this method to send token to your app server.  
 Log.d("MainActivity" ,"sendRegistrationTokenToServer($token)")  
})

/**  
* Called if the FCM registration token is updated. This may occur if the security of * the previous token had been compromised. Note that this is called when the * FCM registration token is initially generated so this is where you would retrieve the token. */
override fun onNewToken(token: String) {  
Log.d(TAG, "Refreshed token: $token")  
 
// If you want to send messages to this application instance or  
// manage this apps subscriptions on the server side, send the // FCM registration token to your app server.
sendRegistrationToServer(token)  
}