Android: keeping a background service alive (preve

Question

I have a service that is defined as:

public class SleepAccelerometerService extends Service implements SensorEventListener

Essentially, I am making an app that monitors accelerometer activity for various reasons while the user sleeps with his or her phone/device on the bed. This is a long-running service that MUST NOT be killed during the night. Depending on how many background apps and periodic processes occur during the night, android sometimes kills off my process, thereby ending my service. Example:

10-04 03:27:41.673: INFO/ActivityManager(1269): Process com.androsz.electricsleep (pid 16223) has died.
10-04 03:27:41.681: INFO/WindowManager(1269): WIN DEATH: Window{45509f98 com.androsz.electricsleep/com.androsz.electricsleep.ui.SleepActivity paused=false}

I do not want to force the user to have 'SleepActivity' or some other activity in my app as the foreground. I can't have my service run periodically, because it is constantly intercepting onSensorChanged.

Any tips? source code is here: http://code.google.com/p/electricsleep/

Answer 1

As Dave already pointed out, you could run your Service with foreground priority. But this practice should only be used when it's absolutely necessary, i.e. when it would cause a bad user experience if the Service got killed by Android. This is what the "foreground" really means: Your app is somehow in the foreground and the user would notice it immediately if it's killed (e.g. because it played a song or a video).

In most cases, requesting foreground priority for your Service is contraproductive!

Why is that? When Android decides to kill a Service, it does so because it's short of resources (usually RAM). Based on the different priority classes, Android decides which running processes, and this included services, to terminate in order to free resources. This is a healthy process that you want to happen so that the user has a smooth experience. If you request foreground priority, without a good reason, just to keep your service from being killed, it will most likely cause a bad user experience. Or can you guarantee that your service stays within a minimal resource consumption and has no memory leaks?¹

Android provides sticky services to mark services that should be restarted after some grace period if they got killed. This restart usually happens within a few seconds.

Image you want to write an XMPP client for Android. Should you request foreground priority for the Service which contains your XMPP connection? Definitely no, there is absolutely no reason to do so. But you want to use START_STICKY as return flag for your service's onStartCommand method. So that your service is stopped when there is resource pressure and restarted once the situation is back to normal.

¹: I am pretty sure that many Android apps have memory leaks. It something the casual (desktop) programmer doesn't care that much about.