Question

When an app sets a repeating alarm and from the users point of view the phone is in normal mode with an alarm in the notification bar what is happening with the code of the app? I assume the values of all the variables are stored in the phone memory in such a way that when the alarm wakes up the original state is restored. Does setting an alarm impose much more demand on the battery?

Answer 1

When an app sets a repeating alarm and from the users point of view the phone is in normal mode with an alarm in the notification bar what is happening with the code of the app?

AlarmManager has nothing to do with the AlarmClock application. There is no “alarm in the notification bar” unless you put something there yourself, which would be a bit unusual for an app employing AlarmManager.

Assuming you are referring to AlarmManager, “what is happening with the code of the app” is it better be shut down. The point behind AlarmManager is so you do not have to keep any code in memory just to watch the clock tick by.

I assume the values of all the variables are stored in the phone memory in such a way that when the alarm wakes up the original state is restored.

That is absolutely incorrect. AlarmManager does nothing of the sort. And, a well-written app using AlarmManager will get the heck out of memory when it is not delivering any immediate value. If you need data to persist between alarms, use databases or files.

Does setting an alarm impose much more demand on the battery?

A _WAKEUP alarm will have an impact on the battery proportional to the frequency with which the alarm goes off. If the alarm is nice and infrequent (e.g., user configured to every 15 minutes), the alarm itself will have little impact, but what you do when the alarm goes off might.