Chat App using Firebase: Get notification when new message received - Android

Question

I am developing a chat app using Firebase Realtime Database. I have been able to send and receive messages properly. Now, I want to implement notification whenever new message is received. For that, I have created a Service which listens to database changes using ChildEventListener and creates notification. The problem is that I am creating notification in onChildAdded method and this method fires both for existing node in database and new one. This is causing notification to be created multiple times for same message whenever user navigate back and forth from app.

Here is how I am implementing it:

chatMsgsRef.orderByChild(FirebaseDBKeys.LOCATION_LAST_UPDATED).addChildEventListener(new ChildEventListener() {              @Override             public void onChildAdded(DataSnapshot dataSnapshot, String s) {                  ChatMessage message = dataSnapshot.getValue(ChatMessage.class);                  if (!message.getSenderId().equals(currentUserId)) {                      mNotificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);                      NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(NotificationsService.this)                             .setSmallIcon(R.drawable.message)                             .setContentTitle("New Message from " + message.getReceipientName())                             .setContentText(message.getMessage())                             .setOnlyAlertOnce(true)                             .setSound(RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION));                     mBuilder.setAutoCancel(true);                     mBuilder.setLocalOnly(false);                       mNotificationManager.notify(NOTIFICATION_ID, mBuilder.build());                  }             }              @Override             public void onChildChanged(DataSnapshot dataSnapshot, String s) {              }              @Override             public void onChildRemoved(DataSnapshot dataSnapshot) {              }              @Override             public void onChildMoved(DataSnapshot dataSnapshot, String s) {              }              @Override             public void onCancelled(DatabaseError databaseError) {              }         }); 

How can I implement notifications in the way it works in other chat applications like whatsapp, etc.??

Answer 1

The correct way to do this is to have a push data message to the client with the chat when there is a new chat sent to them.

This blog post explains how to accomplish this. Basically you need to set up a server to listen to the chat firebase ref and send push notifications when it is updated. This way your clients can be in the app or out of the app and still get the push.

If you use a service there are a number of potential issues.

First of all you will have to keep the phone awake. This will drain the battery.

Second, Android can kill your background service at any time, so your app may stop working suddenly.

Third, with Doze mode Android will block network activity and stop your app from running in the background.