Fragment內嵌套viewPager的方法

public class Main1Fragment extends Fragment {


    private ViewPager viewpager;
    private ArrayList<Fragment> fragments;

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = View.inflate(getActivity(), R.layout.fragment_a, null);
        viewpager = view.findViewById(R.id.viewpager);
        return view;
    }


    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        initFragments();
        viewpager.setAdapter(new MPagerAdapter(getChildFragmentManager()));
    }

    private void initFragments() {
        fragments = new ArrayList<>();
        fragments.add(new Child1Fragment());
        fragments.add(new Child2Fragment());
        fragments.add(new Child3Fragment());
    }

    private class MPagerAdapter extends FragmentPagerAdapter {


        public MPagerAdapter(FragmentManager fm) {
            super(fm);
        }

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

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