Lifecycle of Fragment that holds a ViewPager

Question

I have something that has me stumped. I have a Fragment (Fragment A) that has ViewPager that contains three fragments (for swiping left/right). So, if within another fragment, in the onBackPressed() method, I do a getFragmentManager().popBackStack() call, Fragment A will be again be visible (with the ViewPager of sub-fragments) which is the desired state. However, there is no method with Fragment A or within the ViewPager that indicates that Fragment A/ViewPager is again visible.

None of the fragment methods referenced in the Fragment lifecycle ( http://developer.android.com/guide/components/fragments.html ) that should be called when "The fragment returns the layout from the back stack" or any of the methods called within OnPageChangeListener (yes, I do call viewPager.setOnPageChangeListener(this) within Fragment A's onCreateView).

Thoughts on where I could look?

Answer 1

I have an app with a ViewPager that is added to the layout, then later replaced by another fragment, with the change added to the transaction back stack. I have Log statements in each of the lifecycle methods of the pager. When the Back button is pressed and the pager is returned to the layout, my logcat output shows these methods called for the pager: onCreateView() , onActivityCreated() , onStart() , onResume() . Note that when a fragment goes into the back stack, its view is destroyed, but the fragment object is not destroyed, so when the fragment returns from the back stack, there is no call to onCreate() .

This behavior is consistent with the lifecycle diagram in the Fragment Guide . You should be able to use the call to onResume() as an indication that your pager is visible. I can only suggest that you add debug output to the lifecycle methods for your pager and look at the output. If you think its wrong, please add it to the post of your question. Also indicate what fragment transaction method(s) you are using. If by chance you are using hide() instead of remove() or replace() , then the lifecycle events are different and you may need to use onHiddenChanged() .