Getting a reference to a child Fragment after the parent Fragment has been recreated

Question

Starting Android 4.2, Android supports nested Fragments. The doc doesn't give a lot of explanations regarding nested Fragment lifecycles but from experience, it appears their lifecycle is really similar to "regular" Fragments.

It looks like there is one big difference though: child Fragments are not restored when the parent Fragment onCreate method is called. As a consequence, it seems impossible to save/restore a reference to a particular Fragment:

• Using getChildFragmentManager.findFragmentByTag(String) always returns null in parent Fragment onCreate(Bundle) because mActive is null.
• Using putFragment/getFragment results in a NullPointerException because getFragment looks for the size of a null mActive ArrayList.

So, my question is quite simple. Is there a correct way to retrieve a reference to a child Fragment in the parent Fragment onCreate method?

Answer 1

I don't think you can in onCreate as the view isn't constructed at that time. You can in onViewCreated() though. The logic I used is:

• Check if there is saved state in onViewCreated(), if there is, try to get the child fragment
• Then check if the child fragment is null, if it is, add it using the child fragment manager.

By "checking" I mean looking up the fragment by id. I guess by tag should work too.

AFAIK you can't get a child fragment before the view hierarchy is restored or created, but you could do the same at later time, for example in onActivityCreated()

Answer 2

What about setRetainInstanceState(true) on your fragment? Could it solve your problem? It solved some problems when I have ChildFragments in a Fragment. I only have to keep a reference to the childfragment in the fragment.

But I allways did that in onCreateView(). Not sure if it will work in onCreate()

Or do you mean something completely different?