Question

When an app have been put into the background and later resumes to an activity, is it possible that static class variables set in another Activity could have been reset by the garbage collector and have got the value set to zero?

I use a couple of public static int variables in my main Activity and use them as global variables in various other Activities. I have received a crash report in the developer console from Android Market where the only explanation I can find is that the app resumes to an Activity which uses the value of a public static int variable in another class, but the value has (mysteriously?) become zero. I know that it was set to something else when the app first started. Is this at all possible?

If my suspicion is correct, what is the recommended way to preserve the values of the global variables when an app is put in to background? Save them in SharedPreferences in OnPause() or use onSaveInstanceState or something else?

Answer 1

When an app have been put into the background and later resumes to an activity, is it possible that static class variables set in another Activity could have been reset by the garbage collector and have got the value set to zero?

It would not be “reset by the garbage collector”. However, the process may have been terminated by Android, to free up memory for other applications.

what is the recommended way to preserve the values of the global variables when an app is put in to background?

Static data members should only be a cache. Data you want to retain regardless of what happens (e.g., process being terminated) needs to go in some persistent store, such as a flat file, SharedPreferences, or database. onPause() is a likely time to arrange to persist that data, as any time after that, your process could be terminated without notice.