Android-How to detect on resume that my app was killed by VM?

Question

In my app, when user presses HOME key and returns back to app after some time, my app gives NullPointerExceptions on various places and activities. I know that my app is being killed by OS to free some resources. Now I want that when user comes back again to app and app was previously killed, then how can I detect that my app was killed so that I can reload different resources?

Answer 1

When onCreate (Bundle savedInstanceState) is called, check that savedInstanceState is not null. As stated by onCreate :

savedInstanceState If the activity is being re-initialized after previously being shut down then this Bundle contains the data it most recently supplied in onSaveInstanceState(Bundle). Note: Otherwise it is null.

See also onSaveInstanceState() which is not part of the normal lifecycle but is called before the activity is killed.

Note : if the user does A ----> B ----> C --back--> B ----> C, the second time C is created the passed bundle will be null, as it is a new instance, not the same recreated after being killed.

Answer 2

Basically: look at the picture on this page: http://developer.android.com/reference/android/app/Activity.html

the various functions that are called in different situations are onCreate, onStart and onResume.

Answer 3

My suggestion would be: implement your own Application and if the onCreate() is called, the app was killed in background