Firebase push notification is not received android studio

Question

i'm trying to send notification from android using retrofit and i followed the offical documentation from firebase. i setup retrofit with https://fcm.googleapis.com/fcm/send and when i post notifications retrofit returns response but the message dosen't appear in my logs. i think my service is not working after the message was posted.

MainActivity

const val TOPIC = "MyTopic"

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

        FirebaseMessaging.getInstance().subscribeToTopic(TOPIC)


        val btnSend = findViewById<Button>(R.id.btnSend)

        btnSend.setOnClickListener {
            FirebaseNotificationData(
                NotificationData("Notification title", "Notification message"),
                TOPIC
            ).also {
                postNotification(it)
            }
        }
    }

    private fun postNotification(notification: FirebaseNotificationData) =
        CoroutineScope(Dispatchers.IO).launch {
            val response = RetrofitInstance.api.postNotification(notification)

            if (response.isSuccessful)
                Log.d("Retrofit", "Message was posted")
            else
                Log.e("Retrofit", response.errorBody().toString())
        }
}

Service

class FirebaseNotificationService : FirebaseMessagingService() {

    override fun onMessageReceived(message: RemoteMessage) {
        super.onMessageReceived(message)

        Log.d("onMessageReceived","message received")
    }

}

Manifest

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
   package="com.example.firebasenotification">

   <uses-permission android:name="android.permission.INTERNET" />
   <uses-permission android:name="com.google.android.c2dm.permission.RECEIVE" />

   <application
       android:allowBackup="true"
       android:icon="@mipmap/ic_launcher"
       android:label="@string/app_name"
       android:roundIcon="@mipmap/ic_launcher_round"
       android:supportsRtl="true"
       android:theme="@style/Theme.FirebaseNotification">
       <activity
           android:name=".MainActivity"
           android:exported="true">
           <intent-filter>
               <action android:name="android.intent.action.MAIN" />

               <category android:name="android.intent.category.LAUNCHER" />
           </intent-filter>
       </activity>

       <service android:name=".FirebaseNotificationService"
           android:permission="com.google.android.c2dm.permission.SEND"
           android:exported="true">
           <intent-filter>
               <action android:name="com.google.firebase.MESSAGING_EVENT"/>
               <action android:name="com.google.android.c2dm.intent.RECEIVE"/>
           </intent-filter>
       </service>

   </application>

</manifest>

Answer 1

onMessageReceived is provided for most message types, with the following exceptions:

Notification messages delivered when your app is in the background. In this case, the notification is delivered to the device’s system tray. A user tap on a notification opens the app launcher by default.

Messages with both notification and data payload, when received in the background. In this case, the notification is delivered to the device’s system tray, and the data payload is delivered in the extras of the intent of your launcher Activity.

While testing, make sure the app is in background, when you send FCM notifications.

https://firebase.google.com/docs/cloud-messaging/android/receive