Question

Hello I am just a little confused after reading these materials on Tasks and Back Stack, Android Developer Guide:

It says:

When Activity A starts Activity B, Activity A is stopped, but the system retains its state (such as scroll position and text entered into forms). If the user presses the Back button while in Activity B, Activity A resumes with its state restored.

While in the APIs reference for onSaveInstanceState() method, it says:

One example of when onPause() and onStop() is called and not this method is when a user navigates back from activity B to activity A: there is no need to call onSaveInstanceState(Bundle) on B because that particular instance will never be restored, so the system avoids calling it.

The above two situations seem identical to me (“press the Back button to Activity A” and “navigate back from Activity B to Activity A”). But I don’t understand why while the former says Activity A resumes with its previous state restored while the latter says the particular instance of Activity B will never be restored. Any explanations?

Thanks in advance!

Answer 1

I think the first one is saying that A will be saved so it can be restored, and the second one is saying that B will not be saved because it can’t be restored.