onStop vs onDestroy

Question

I have tried to research exactly when the onDestroy method is called for an activity, but I've read some confusing and conflicting information. In general, my question is: under what circumstances is the onDestroy method actually called on an activity? More specifically, if I have two activities, activity A and activity B, if activity A is running and I create an intent and switch to activity B, is activity A only stopped, or is it destroyed?

Answer 1

Like stated in the official documentation:

onDestroy()

The final call you receive before your activity is destroyed. This can happen either because the activity is finishing (someone called finish() on it, or because the system is temporarily destroying this instance of the activity to save space. You can distinguish between these two scenarios with the isFinishing() method.

In your example the Activity A is stopped and could be destroyed by the System

---

Note per documentation link above:

…do not count on [onDestroy()] being called as a place for saving data … [see] either onPause() or onSaveInstanceState(Bundle).

Answer 2

onDestroy() is called whenever:

• The user takes out the activity from the "recent apps" screen.
• The user takes out the activity from the "recent apps" screen.

onStop() is called whenever:

• The user leaves the current activity.

So in your example, when the user launches Activity B, Activity A called onStop().

EDIT: The onDestroy() method is not always being called, according to the documentation. onStop() is always called beginning with Honeycomb, so move code you explicitly need to do before the activity stops to there.

Starting with Honeycomb, an application is not in the killable state until its onStop() has returned. https://developer.android.com/reference/android/app/Activity#ActivityLifecycle

Hope this helped :D