public void onMessageReceived(RemoteMessage remoteMessage) {
        SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
        String opcija = sharedPreferences.getString("opcija", null);
        if(opcija.contains("1")){
            showNotification(remoteMessage.getData().get("poruka"));
        } else {
            showNotification(remoteMessage.getData().get("poruka"));
        }
    }

    private void showNotification(String poruka) {
        Intent i = new Intent(this, MainActivity.class);
        i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);

        PendingIntent pendingIntent = PendingIntent.getActivity(this,0,i,PendingIntent.FLAG_UPDATE_CURRENT);
        NotificationCompat.Builder builder = new NotificationCompat.Builder(this)
                .setAutoCancel(true)
                .setContentTitle("Obavijest")
                .setContentText(poruka)
                .setContentIntent(pendingIntent);
        NotificationManager manager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
        manager.notify(0,builder.build());
    }