title: Why will my android notification not send?
body: <p>I am sending DATA payload from Postman, so the notification should be processed in onMessageReceived regardless of whether the app is in foreground or background.</p>
  
  <p>According my logs and testing, onMessageReceived is fired, but the notifications are not showing (doesn't depend if the app is in foreground or background).</p>
  
  <p>in manifest I have:</p>
  
  <pre><code>&lt;service
          android:name=".MyFirebaseMessagingService"
          android:exported="false"&gt;
          &lt;intent-filter&gt;
              &lt;action android:name="com.google.firebase.MESSAGING_EVENT" /&gt;
          &lt;/intent-filter&gt;
      &lt;/service&gt; &lt;!-- [END firebase_iid_service] --&gt;
      &lt;service
          android:name=".MyFirebaseInstanceIDService"
          android:exported="false"&gt;
          &lt;intent-filter&gt;
              &lt;action android:name="com.google.firebase.INSTANCE_ID_EVENT" /&gt;
          &lt;/intent-filter&gt;
      &lt;/service&gt;
  </code></pre>
  
  <p>and here is MyFirebaseMessagingService.java:</p>
  
  <pre><code>public class MyFirebaseMessagingService extends FirebaseMessagingService {
  
      @Override
      public void onMessageReceived(@NonNull RemoteMessage remoteMessage) {
          super.onMessageReceived(remoteMessage);
  
          String title = "";
          if (Objects.requireNonNull(remoteMessage.getData()).get("title") != null)
              title = remoteMessage.getData().get("title");
  
          String message = "";
          if (Objects.requireNonNull(remoteMessage.getData()).get("message") != null)
              message = remoteMessage.getData().get("message");
  
          Log.e("notification",title);
          sendNotification(title, message);
      }
  
      private void sendNotification(String title, String body) {
  
          Intent i = new Intent(this, Novinky.class);
          i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
          PendingIntent pi = PendingIntent.getActivity(this,
                  0, // Request code
                  i,
                  PendingIntent.FLAG_ONE_SHOT);
  
          Uri sound = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
  
          NotificationCompat.Builder builder = new NotificationCompat.Builder(this,
              getString(R.string.default_notification_channel_id))
                  .setSmallIcon(R.mipmap.ic_notify)
                  .setContentTitle(title)
                  .setContentText(body)
                  .setAutoCancel(true)
                  .setSound(sound)
                  .setContentIntent(pi);
  
          NotificationManager manager =
                  (NotificationManager) this.getSystemService(Context.NOTIFICATION_SERVICE);
  
          assert manager != null;
          manager.notify(0, builder.build());
      }
  }
  </code></pre>
  
  <p>So I have Log.e("notification",title); there, and it is executed properly, but the notify is not received.</p>
  
  <p>Before I send also a notification+data via Postman, that worked, but that is only an automatic notification not handled by app, so now I want to send only DATA payload and handle it in the app, but for some reason it doesn't work.</p>