Your goal cannot be stably achieved by your approach. If you use an Handler's postDelayed()
method and the CPU goes to deepsleep, the ms counter will stop and will only continue if the CPU wakes up again.
So if you want to have some kind of a cron job you will need to use wakelock. Fortunately there is a Service implementation that does exactly that: Wakeful IntentService
From the doc:
The recommended pattern for Android's equivalent to cron jobs and Windows scheduled tasks is to use AlarmManager. This works well when coupled with an IntentService, as the service will do its work on a background thread and shut down when there is no more work to do. There's one small problem: IntentService does nothing to keep the device awake. If the alarm was a WAKEUP variant, the phone will only stay awake on its own while the BroadcastReceiver handling the alarm is in its onReceive() method. Otherwise, the phone may fall back asleep. WakefulIntentService attempts to combat this by combining the ease of IntentService with a partial WakeLock.