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I have created an Android service which basically does the following:

schedule a task, using the ScheduledThreadPoolExecutor.schedule() method
when the schedule time is reached, the task is executed and a new schedule is started

Thus, the service continuously has a timer in place (except during execution of the task); sometimes 2 (independent) timers are in place, depending on the result of the task. The service should be running all the time and executes different tasks from time to time.

All seems to work ok (at least when running with DDMS), but after a while (something like an hour without connecting the device via DDMS) the timer tasks are not executed anymore. The only way to get it working again is either stopping and starting the service again or by connecting the device with DDMS (using Eclipse); waking up the device only does not trigger this.

It looks like, Android sets the service in a kind of sleep mode (service is still running when looking at the Active Services on the device).

My question is: how do I prevent this behavior and keep the service working all the time?

I did some research and I found something which theoretically could give a solution, by acquiring a (PARTIAL_WAKE_LOCK) WakeLock in the service, but as far as I understand, using this solution, I have to acquire the lock at the onStartService() method and release it at onDestroy(), meaning that I keep the lock during the lifetime of the service (which is forever); I suspect a battery drainage using this method.

Is there another way to accomplish the same?

hatemp
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4 Answers4

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I have solved the problem, thanks to the replies above.

I switched from the ScheduledPoolThreaExecutor() to the AlarmManager. Together with the RTC_WAKEUP type all triggers are handled now.

I did not use the IntentService, because my service has to do things in parallel based on alarms (and IntentService implements a queued solution). The original service, which was staying alive all the time in the original implementation, is now only created whenever an alarm is triggered.

I also have the impression (but that is only a gut feeling, not based on real measurements, that this new implementation (where the service is created when needed and is not alive all the time (waiting on timer evens), is even better for battery life of the device.

hatemp
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How often to you need to execute, and what do you mean by running all the time? I guess that you don't mean be executing all the time?

I have a service that does this, and it works quite well:

It schedules an alarm with the alarm manager. Acquires a wakelock when the alarm is triggered, performs some work, and then schedules a new alarm before releasing the wake lock.

Kaj
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  • At the moment, one task is executing every 5 minutes; the other task runs about 5 times/day, but this is depending on the results of the other task (could theoretically run every 5 minutes). – hatemp Jul 28 '11 at 11:01
  • I mean with running all the time, that the service is running, but only awaits wake up triggers from the timers (therefore service is doing nothing most of the time). – hatemp Jul 28 '11 at 11:03
  • Using the AlarmManager results in creation of at 3 different services (because there are 3 different tasks to perform); logic of the operation at this moment is such that one task influences the next one, therefore logic to do this is spread around these services, whereas the one service now contains all logic and binds this together. Can the same not be achieved by using ScheduledThreadPoolExecutor class? – hatemp Jul 28 '11 at 11:17
  • No, you don't need 3 different services. See this thread: http://stackoverflow.com/questions/3273342/how-can-i-setup-multiple-alarms-in-android. And no, you shouldn't use ScheduledThreadPoolExecutor. The benefit of using the alarm manager is that you can schedule an alarm, then kill your process, and only wakeup when you should execute. That means that you don't consume any resources while you aren't executing. – Kaj Jul 28 '11 at 11:54
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Use IntentService for your service implementation and register pending intents with AlarmManager to trigger those intents on the time basis you need.

Naresh
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I have used wake locks in an app before and I did not need to release them in the onDestroy(), I literally had the following and it worked perfectly:

onClockListener{
   acquire wakelock
   method call
}

otherOnClickListener{
   release wakelock
   other method call
}

Not sure if it will help much but it definitely wont help if I don't post anything :)

Ian
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