MyFirebaseMessagingService.java

public class MyFirebaseMessagingService extends FirebaseMessagingService {

    private static final String TAG = "MyFirebaseMsgService";

    @Override
    public void onMessageReceived(RemoteMessage remoteMessage) {
        super.onMessageReceived(remoteMessage);
        Log.d(TAG, "From: " + remoteMessage.getFrom());

        if (remoteMessage.getData().size() > 0) {
            Log.d(TAG, "Message data payload: " + remoteMessage.getData());
        }

        if (remoteMessage.getNotification() != null) {
            Log.d(TAG, "Message Notification Body: " + remoteMessage.getNotification().getBody());
        }
        sendNotification(remoteMessage.getNotification());
    }

    private void sendNotification(RemoteMessage.Notification message) {
        Intent intent = new Intent(this, MainActivity.class);
        intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
        PendingIntent pendingIntent = PendingIntent.getActivity(this, 0 /* Request code */, intent,PendingIntent.FLAG_ONE_SHOT);

        Uri defaultSoundUri = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
        NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(this)
                .setSmallIcon(R.drawable.ic_notifications_black_24dp)
                .setContentText(message.getBody())
                .setAutoCancel(true)
                .setSound(defaultSoundUri)
                .setVibrate(new long[]{1000,1000})
                .setContentIntent(pendingIntent);
        if(message.getTitle()!=null){
            notificationBuilder.setContentTitle(message.getTitle());
        }else{
            notificationBuilder.setContentTitle(getResources().getString(R.string.app_name));
        }

        NotificationManager notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);

        notificationManager.notify(0 /* ID of notification */, notificationBuilder.build());
    }

}