android - Run code every day at a specific time - AlarmManager

Question

Currently, I am trying to run a piece of code at a specific time. After some research, I think the correct way to go is to make usage of the AlarmManger. The code should be executed every day at 3 am. If the phone is at 3 am shut down, the code should be executed directly after turning the phone on.

I used googled and found a lot of results. But my code isn't working correctly.

Yesterday I got a notification. The notification time was 10 pm. But in the code, the time is set to 3 am. I set up a lot of alarm manager over the time (because of testing). Could it be possible, that the triggered AlarmManager was an old one? Note: Before setting up a new AlarmManager I deleted the complete application from my phone and installed it new. (I think this will delete all set AlarmManager's?)

Okay, here is the code I am using:

Calendar calendar = Calendar.getInstance();
calendar.setTimeInMillis(System.currentTimeMillis());
calendar.add(Calendar.SECOND, 0);
calendar.add(Calendar.MINUTE, 0);
calendar.add(Calendar.HOUR, 3);

Intent _myIntent = new Intent(MainActivity.this, AlarmReceiver.class);
_myIntent.putExtra("MyMessage","Content of the message");
PendingIntent pendingIntent = PendingIntent.getBroadcast(MainActivity.this, 123, _myIntent, PendingIntent.FLAG_UPDATE_CURRENT);

AlarmManager alarmManager = (AlarmManager) MainActivity.this.getSystemService(Context.ALARM_SERVICE);
alarmManager.setRepeating(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis(), 1000*60*60*24, pendingIntent);

Answer 1

Note: as of API 19, all repeating alarms are inexact. If your application needs precise delivery times then it must use one-time exact alarms, rescheduling each time.

Inexact scheduling means the time between any two successive firings of the alarm may vary. Thats what happening in your case i guess.To overcome the exact time issue i think you should use one shot alarm.But in this case you need to reschedule it for next day. and so on. You can get a very clear understanding from the Documentation setrepeating , setInexactRepeating.

EDIT:- TO optimizing DOZE mode In Case you are Using setAndAllowWhileIdle() or setExactAndAllowWhileIdle(), Then you must read This Document which says :-

Neither setAndAllowWhileIdle() nor setExactAndAllowWhileIdle() can fire alarms more than once per 9 minutes, per app.