How to set a ViewPager inside a Fragment

I need to place a ViewPager inside of a fragment, but I have two fragments, Fragment 1 is my MENU, and Fragment 2 I want to use as a ViewPagerIndicator.

But a fragment can't have another fragment... what do I need to do for that?

Starting in Android 4.2, there are nested fragments.http://developer.android.com/about/versions/android-4.2.html#NestedFragments The support library now also includes support for this for older Android versions.

So you can do something like this:

@Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);

    ViewPager mViewPager = (ViewPager) view.findViewById(R.id.viewPager);
    mViewPager.setAdapter(new MyAdapter(getChildFragmentManager()));
    }

Full implementation available here: https://github.com/marcoRS/nested-fragments/tree/master/src/com/burnside/digital/nestedfragments

You must use getChildFragmentManager() instead of getSupportFragmentManager() to get the FragmentManger inside a Fragment. But you should not use FragmentStatePagerAdapter rather than FragmentPagerAdapter.

Just use getChildFragmentManager() instead of getSupportFragmentManager() inside Fragments.

Inside Fragments

new ViewPagerAdapter(getChildFragmentManager());

Inside Activity

new ViewPagerAdapter(getSupportFragmentManager());

Simple Code

fragment_sample.xml layout

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <com.google.android.material.tabs.TabLayout
        android:id="@+id/tablayout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <androidx.viewpager.widget.ViewPager
        android:id="@+id/viewpager"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1" />

</LinearLayout>

SampleFragment.java class

public class SampleFragment extends Fragment {
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View fragmentView = inflater.inflate(R.layout.fragment_sample, container, false);
        return fragmentView;
    }

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        // find views by id
        ViewPager viewPager = view.findViewById(R.id.viewpager);
        TabLayout tabLayout = view.findViewById(R.id.tablayout);

        // attach tablayout with viewpager
        tabLayout.setupWithViewPager(viewPager);

        ViewPagerAdapter adapter = new ViewPagerAdapter(getChildFragmentManager());

        // add your fragments
        adapter.addFrag(new SampleFragment(), "Tab1");
        adapter.addFrag(new SampleFragment2(), "Tab2");
        adapter.addFrag(new SampleFragment3(), "Tab3");

        // set adapter on viewpager
        viewPager.setAdapter(adapter);
    }
}

ViewPagerAdapter.java class

// common adapter for all view pager in your project.
public class ViewPagerAdapter extends FragmentStatePagerAdapter {
    private final List<Fragment> mFragmentList = new ArrayList<>();
    private final List<String> mFragmentTitleList = new ArrayList<>();

    public ViewPagerAdapter(FragmentManager manager) {
        super(manager);
    }

    @Override
    public Fragment getItem(int position) {
        return mFragmentList.get(position);
    }

    @Override
    public int getCount() {
        return mFragmentList.size();
    }

    @Override
    public CharSequence getPageTitle(int position) {
        return mFragmentTitleList.get(position);
    }

    public void addFrag(Fragment fragment) {
        mFragmentList.add(fragment);
        mFragmentTitleList.add("");
    }

    public void addFrag(Fragment fragment, String title) {
        mFragmentList.add(fragment);
        mFragmentTitleList.add(title);
    }
}

Important Related Links

• Difference between getSupportFragmentManager() and getChildFragmentManager()?
• getSupportFragmentManager() versus getFragmentManager() in android 3.0+
• Difference between FragmentPagerAdapter and FragmentStatePagerAdapter