CountDownTimer does not run in service after app is swiped from recents?

Question

I am trying to show a notification to count down the seconds until my CountDownTimer ends within a service - and works ok until I swipe my app away from the recents menu. It then gets stuck on the second that it is on. I am using startForeground() . What am I doing wrong? Tested on both my OnePlus 5t and the Google pixel emulator.

public class PersistentNotificationService extends Service {

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        showPersistentNotification();
        return Service.START_STICKY;
    }

    void showPersistentNotification() {
        Intent intent = new Intent(this, MainActivity.class);
        PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, intent, 0);

        NotificationCompat.Builder builder = new NotificationCompat.Builder(this, "persistentNotification");
        builder.setAutoCancel(true)
                .setDefaults(Notification.DEFAULT_ALL)
                .setWhen(System.currentTimeMillis())
                .setAutoCancel(true)
                .setOnlyAlertOnce(true)
                .setContentIntent(pendingIntent)
                .setColor(Color.parseColor("#0097A7"))
                .setSmallIcon(R.mipmap.ic_launcher)
                .setOngoing(true)
                .setVibrate(new long[0])
                .setContentTitle("Time until period ends");

        NotificationManager notificationManager = (NotificationManager) this.getSystemService(Context.NOTIFICATION_SERVICE);
        startForeground(0, builder.build());
        new CountDownTimer(30000, 1000) {

            public void onTick(long millisUntilFinished) {
                builder.setContentText(millisUntilFinished / 1000 + " seconds until period ends");
                notificationManager.notify(1, builder.build());
            }

            public void onFinish() {
                showPersistentNotification();
            }
        }.start();
    }

    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }
}

Answer 1

Ok, so after all, the only issue was the fact that I needed to pass an ID above zero when I call startForeground .

Changed this: startForeground(0, builder.build()); to this: startForeground(1, builder.build());