android - Why it is not possible to use ViewPager within a Fragment? It actually is

Question

There are information that it is impossible to use ViewPager within a Fragment in many sources like "The Busy Coders Guide for Android Developers" by Mark Murphy, or posts like this on SO. I'm confused because I don't have such a problem and I successfully use ViewPager within my Fragment. The only distinction is that I instantiate a ViewPager not in onCreateView() method but in onActivityCreated(). And everything works perfectly fine.

So the question is - may be I just don't know something and this is not recommended for some reason to make UI instantiations in onActivityCreated()? But again - everything works just fine.

Here is the listing of the class and xml:

Class:

public class ViewPagerFragment extends Fragment {

    static final int NUM_ITEMS = 2;

    private ViewPagerAdapter mAdapter;
    private ViewPager mPager;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        return inflater.inflate(R.layout.view_pager_fragment, container, false);
    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);

        mAdapter = new ViewPagerAdapter(getFragmentManager());

        mPager = (ViewPager) getView().findViewById(R.id.pager);
        mPager.setAdapter(mAdapter);
    }

    public static class ViewPagerAdapter extends FragmentPagerAdapter {
        public ViewPagerAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int num) {
            if (num == 0) {
                return new ItemsListFragment();
            } else {
                return new FavsListFragment();
            }
        }

        @Override
        public int getCount() {
            return NUM_ITEMS;
        }
    }
}

Layout:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="fill_parent"
              android:layout_height="fill_parent"
              android:orientation="vertical">

    <android.support.v4.view.ViewPager
        android:id="@+id/pager"
        android:layout_width="fill_parent"
        android:layout_height="0dp"
        android:layout_weight="1"/>

</LinearLayout>

Answer 1

To implement the View pager within a fragment use getChildFragmentManager() instead of getFragmentManager(). You can call setAdapter() for the ViewPager from onCreateView() or onViewCreated(), that is not a matter.

I hope this will help you guys.