AlarmManager only works after App restart

Question

I made an AlarmManager which starts a Service at a specific time and every 30 Minutes after that. The Service starts a notification. The Problem is, that I only get the Notification after I restarted the Application. The notification works but the AlarmManger doesn't because I get the Notification everytime after I restarted the app. It doesn't matter when I restart the app, I get the notification every time.

Heres my AlarmManger code:

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);


    Intent myIntent = new Intent(MainActivity.this , MyAlarmService.class);
    alarmManager = (AlarmManager)getSystemService(ALARM_SERVICE);
    pendingIntent = PendingIntent.getService(MainActivity.this, 0, myIntent, 0);

    Calendar calendar = Calendar.getInstance();
    calendar.setTimeInMillis(System.currentTimeMillis());
    calendar.set(Calendar.HOUR_OF_DAY, 19);
    calendar.set(Calendar.MINUTE, 4);

    alarmManager.setInexactRepeating(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis(),
            AlarmManager.INTERVAL_HALF_HOUR, pendingIntent);
}

Here is my Notification Code:

public class MyAlarmService extends Service {

@Override

public void onCreate() {

    Intent intent1 = new Intent(this, MainActivity.class);
    intent1.putExtra("EXTRA_EVENT_ID", 101);
    PendingIntent pI = PendingIntent.getActivity(this, 0, intent1, 0);
    Notification noti =
            new NotificationCompat.Builder(this)
                    .setSmallIcon(R.mipmap.logo)
                    .setContentTitle(gr)
                    .setContentText(r)
                    .setDefaults(Notification.DEFAULT_ALL)
                    .setStyle(bigStyle)
                    .extend(wearableExtender)
                    .build();

    NotificationManagerCompat nM = NotificationManagerCompat.from(this);
    nM.notify(0,noti);
}

Answer 1

Try setting your alarmManager to setRepeating(), like so

alarmManager.setRepeating(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis(),
        AlarmManager.INTERVAL_HALF_HOUR, pendingIntent);

or

alarmManager.setRepeating(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis(),
        (30*60*1000), pendingIntent);