Question

Besides setting and exact time (i.e. midnight) versus setting a delay (i.e. 24 hours), what’s the difference between using AlarmManager and ScheduledExecutorService to run a task periodically?

In my case, I need to run a little bit of code to check for new data every night and create a new notification if there is new data.

Thanks!

Answer 1

ScheduledExecutorService runs in your application process. If application process dies, none of the scheduled tasks will run. Hence the need for Service (so your process lives beyond Activities active part of lifecycle).

While AlarmManager is critical system service that runs all the time. And if your application scheduled something and was killed, then AlarmManager may start application again (via PendingIntent).

And the last major difference that no one mentioned here is that AlarmManager knows about WakeLocks and power management. This means that AlarmManager may wake up Android device at specified time to run scheduled task. While ScheduledExecutorService knows nothing about power management and will only start task when device is not in deep sleep (i.e. it can simply miss the time).