public class IndexedFragmentPagerAdapter extends FragmentPagerAdapter {
    public SparseArray<Fragment> fragments = new SparseArray<>();

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

    @Override
    public Fragment getItem(int position) {
        return null;
    }

    @Override
    public int getCount() {
        return 0;
    }

    @Override
    public Object instantiateItem(ViewGroup container, int position) {
        Fragment fragment = (Fragment) super.instantiateItem(container, position);
        fragments.put(position, fragment);
        return fragment;
    }

    @Override
    public void destroyItem(ViewGroup container, int position, Object object) {
        fragments.remove(position);
        super.destroyItem(container, position, object);
    }

    public Fragment getRegisteredFragment(int position) {
        return fragments.get(position);
    }
}