Question

I am trying to implement a ‘resume’ feature for a game I’m developing. It should work as follows:

• If the user starts a game and later closes the game with finishing, the game state is saved. When opening the app again, a ‘resume’ option will be available.

• If the activity is only paused (e.g. minimized due to a phone call) and the user returns, it should show the game in progress. It should not terminate and save the state, unless of course, the OS decides to kill the activity.

I’ve decided to use SharedPreferences for the most part, as well as a custom file to save extra information. I’ve seen a lot of people recommend saving the state of the program in the onPause() method and I’ve been wondering why this is the case.

From what I can gather, using OnDestroy() would be better. onPause() does not mean the activity will be killed so I could be wasting time when saving the game state necessarily. I’ve checked my program and onDestroy() is being called at the appropriate times. I’m assuming therefore I have no leak keeping the activity from being destroyed.

Despite this, I cannot find anywhere recommending to save state in onDestroy() and everyone seems to recommend using onPause. Am I missing a piece of information here?

Answer 1

Despite this, I cannot find anywhere recommending to save state in onDestroy() and everyone seems to recommend using onPause. Am I missing a piece of information here?

You are :). onDestroy() is not guaranteed to be called. See the documentation for it:

Note: do not count on this method being called as a place for saving data! For example, if an activity is editing data in a content provider, those edits should be committed in either onPause() or onSaveInstanceState(Bundle), not here. This method is usually implemented to free resources like threads that are associated with an activity, so that a destroyed activity does not leave such things around while the rest of its application is still running. There are situations where the system will simply kill the activity’s hosting process without calling this method (or any others) in it, so it should not be used to do things that are intended to remain around after the process goes away.