I wrote a simple android app in Android Studio. It shows a button that starts a timer that plays a sound every X minutes until stopped with another button.

I use the following code that ran fine up to API33 – but if I test is on API34 or API35 it will finish the mButtonStart routine and the the app will crash.

Can anyone put me on the right track?

        mButtonStart.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if (!timerRunning) {
                mZeitSlider.setVisibility(View.INVISIBLE);
                mButtonStart.setVisibility(View.INVISIBLE);
        
                startTimer(zeitInMinuten[0]*60000);
                vibrator.vibrate(100);
                mtextViewRemark.setVisibility(View.VISIBLE);
                mTextAnstelleButton.setVisibility(View.VISIBLE);
                getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
            }
        }
    });

    private void startTimer(long reminderRate) {
    timerRunning = true;
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
        startForegroundService(new Intent(MainActivity.this, MyService.class));
    }
    else {
        //startService(new Intent(MainActivity.this, MyService.class));
    }
    startAlert(reminderRate);
}


    public void startAlert(long reminderRate) { //as alternative to service
    Intent intent = new Intent(this, MyBroadcastReceiver.class);
    if (Build.VERSION.SDK_INT >= 23) {
        PendingIntent pendingIntent = PendingIntent.getBroadcast(this.getApplicationContext(), myRequestCode, intent, PendingIntent.FLAG_IMMUTABLE);
        AlarmManager alarmManager = (AlarmManager) getSystemService(ALARM_SERVICE);
        try {
            alarmManager.setRepeating(AlarmManager.ELAPSED_REALTIME_WAKEUP, 3000, reminderRate, pendingIntent);
        } catch(Exception e) { e.printStackTrace(); }
    }
}