FragmentManager is already executing transactions. When is it safe to initialise pager after commit?

Question

I have an activity hosting two fragments. The activity starts off showing a loader while it loads an object. The loaded object is then passed to both fragments as arguments via newInstance methods and those fragments are attached.

final FragmentTransaction trans = getSupportFragmentManager().beginTransaction(); trans.replace(R.id.container1, Fragment1.newInstance(loadedObject)); trans.replace(R.id.container2, Fragment2.newInstance(loadedObject)); trans.commit(); 

The second fragment contains a android.support.v4.view.ViewPager and tabs. onResume we initialise it like follows

viewPager.setAdapter(adapter); viewPager.setOffscreenPageLimit(adapter.getCount()); //the count is always < 4 tabLayout.setupWithViewPager(viewPager); 

The problem is android then throws

java.lang.IllegalStateException: FragmentManager is already executing transactions

With this stack trace: (I took android.support out of the package names just for brevity)

v4.app.FragmentManagerImpl.execSingleAction(FragmentManager.java:1620) at v4.app.BackStackRecord.commitNowAllowingStateLoss(BackStackRecord.java:637) at v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:143) at v4.view.ViewPager.populate(ViewPager.java:1235) at v4.view.ViewPager.populate(ViewPager.java:1083) at v4.view.ViewPager.setOffscreenPageLimit(ViewPager.java:847)

The data shows if setOffscreenPageLimit(...); is removed. Is there another way to avoid this issue?

When in the lifecycle is the fragment transaction complete so that I can wait to setup my pager?

Answer 1

Simply use childFragmentManger() for viewpager inside a Fragment

mPagerAdapter = new ScreenSlidePagerAdapter(getChildFragmentManager()); mPager.setAdapter(mPagerAdapter);