gistfile1.txt

public class MyFirebaseService extends FirebaseMessagingService {
    private static final String TAG = "MyFirebaseService";

    @Override
    public void onMessageReceived(RemoteMessage remoteMessage) {
        // handle a notification payload.
        if (remoteMessage.getNotification() != null) {
            Log.d(TAG, "Message Notification Body: " + remoteMessage.getNotification().getBody());
            
            sendNotification(remoteMessage.getNotification().getBody());
        }
    }

    @Override
    public void onNewToken(String token) {
        Log.d(TAG, "Refreshed token: " + token);

        sendRegistrationToServer(token);
    }

    private void sendRegistrationToServer(String token) {
        // TODO: Implement this method to send token to your app server.
    }

    private void sendNotification(String messageBody) {
        Intent intent = new Intent(this, MainActivity.class);
        intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
        PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, intent, PendingIntent.FLAG_ONE_SHOT);

        String channelId = getString(R.string.project_id);
        Uri defaultSoundUri = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);

        NotificationCompat.Builder notificationBuilder =
                new NotificationCompat.Builder(this, channelId)
                        .setSmallIcon(R.drawable.ic_launcher_background)
                        .setLargeIcon(BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher_background))
                        .setContentTitle(getString(R.string.project_id))
                        .setContentText(messageBody)
                        .setAutoCancel(true)
                        .setSound(defaultSoundUri)
                        .setContentIntent(pendingIntent)
                        .setDefaults(Notification.DEFAULT_ALL)
                        .setPriority(NotificationManager.IMPORTANCE_HIGH)
                        .addAction(new NotificationCompat.Action(
                                android.R.drawable.sym_call_missed,
                                "Cancel",
                                PendingIntent.getActivity(this, 0, intent, PendingIntent.FLAG_CANCEL_CURRENT)))
                        .addAction(new NotificationCompat.Action(
                                android.R.drawable.sym_call_outgoing,
                                "OK",
                                PendingIntent.getActivity(this, 0, intent, PendingIntent.FLAG_CANCEL_CURRENT)));

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

        // Since android Oreo notification channel is needed.
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            NotificationChannel channel = new NotificationChannel(
                    channelId,
                    "Channel human readable title",
                    NotificationManager.IMPORTANCE_DEFAULT);

            notificationManager.createNotificationChannel(channel);
        }

        notificationManager.notify(0, notificationBuilder.build());
    }
}