Handling the backstack with fragments containing tabs

Question

I'm trying to create an Android application which contains a single activity with a container and a navigation drawer. The initialy empty container loads fragments which has a ViewPager inside a tab layout in which I load a frgment with a FragmentTransaction:

public static void replaceFragmentInContainer(FragmentManager fragmentManager, Fragment fragmentToShow,
        boolean addToBackStack)
{
    FragmentTransaction transaction = fragmentManager.beginTransaction();
    if (addToBackStack)
    {
        transaction.addToBackStack(null);
    }
    transaction.replace(R.id.container, fragmentToShow);
    transaction.commit();
}

I'm using v4 fragments with a v7 ActionBar in a v7 ActionBarActivity.

Every loaded fragment is a fragment which only loads tabs with other fragments which they hold the actual usability. An example of such tab loading fragment:

public class MainFragment extends TabsFragment
{
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
    {
        super.onCreateView(inflater, container, savedInstanceState);
        View contentView = inflater.inflate(R.layout.fragment_main, container, false);
        initTabsLayout(savedInstanceState, contentView, R.id.pager);
        addTab("tabspectag1", "", R.drawable.draw1, Fragment1.class, null);
        addTab("tabspectag2", "", R.drawable.draw2, Fragment2.class, null);
        addTab("tabspectag3", "", R.drawable.draw3, Fragment3.class, null);
        return contentView;
    }

The problem I'm facing is with the backstack. When a fragment is added to the backstack and I press the back button, the app does go back to the previous fragment like I want to and I see the tabs layout itself, but the content of the tabs is empty like there was nothing loaded to that tab. When it happens, I manage to reload the tab's content only when choosing that screen again with the navigational drawer.

I've tried overriding the onBackPressed in the activity:

@Override
public void onBackPressed()
{
    if (getFragmentManager().getBackStackEntryCount() > 0)
    {
        getFragmentManager().popBackStack();
    } else
    {
        super.onBackPressed();
    }
}

but that like I said, it's like I'm getting back to the previous fragment but the tab inside that fragment is not repainting the fragment it had.

What can be done to solve this issue?

Since I DO see the tabs layout of the original fragment in the backstack but not the fragment inside the tab, is it possible I just need to somehow refresh the tab content meaning repaint it? If I can do such a thing then how can I do it?

score 2 · Answer 1 · answered Jun 02 '15 at 13:22

You didn't post the entire code but, bear in mind that when using fragments inside fragments, the outer fragment should use the childfragmentmanager instead of the regular fragment manager.

If you have an Activity, then you have a fragment that has a Viewpager and inside that viewpager the views are fragments, those outer fragments must use their own childfragmentmanager instead of the activities fragmentmanager.

Activity uses getFragmentManager() to instantiate and show new fragments. Fragments use getChildFragmentManager() to instantiate and show new inner fragments. (fragments inside fragments).

If you always use the same fragmentmanager to handle the transactions the behaviour will be unpredictable.

Your Viewpager should have an TabsAdapter associated that extends from FragmentStatePagerAdapter to show new fragments(and uses the getChildFragmentManager from the fragment instead of the activity).

I think I might have narrowed down the problem and started a new question about it if you want to try answer it: http://stackoverflow.com/questions/30618497/force-viewpager-to-call-getitem-when-going-up-the-backstack — CodeMonkey, Jun 03 '15 at 11:15

Handling the backstack with fragments containing tabs

1 Answers1