RecyclerView infinite scroll not working inside ViewPager2

0

I have a horizontal ViewPager2. On the second slide of the view pager, I have a RecyclerView that has infinite scrolling implemented. I used EndlessRecyclerViewScrollListener to implement infinite scroll.

However, when scrolling down this RecyclerView, it doesn't trigger infinite scrolling. Page 2 of the infinite scroll is never called, only page 1.

Here is my class with the ViewPager2:

public class BaseBottomNavigationViewActivity extends BaseActivity implements BottomNavigationView.OnNavigationItemSelectedListener {

    // The number of pages in the bottom navigation view
    private static final int NUM_PAGES = 5;

    // The view pager
    private ViewPager2 viewPager;

    // The pager adapter
    private FragmentStateAdapter pagerAdapter;

    // The bottom navigation view
    private BottomNavigationView bottomNavigationView;

    private NewPostBottomSheetDialogFragment newPostModalDialog;

    private RelativeLayout newPostButton;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        viewPager = findViewById(R.id.view_pager);
        bottomNavigationView = findViewById(R.id.bottom_navigation_view);

        // The number of screens to keep in memory
        viewPager.setOffscreenPageLimit(5);

        // Disable swiping in the view pager
        viewPager.setUserInputEnabled(false);

        // Set the pager adapter
        pagerAdapter = new BottomNavigationViewPagerAdapter(this);
        viewPager.setAdapter(pagerAdapter);

        // Register the item selected listener
        bottomNavigationView.setOnNavigationItemSelectedListener(this);

        // Set default selection (home)
        bottomNavigationView.setSelectedItemId(R.id.action_first);
    }

    @Override
    protected int getLayoutResource() {
        return R.layout.activity_base_bottom_navigation_view;
    }

    @Override
    public boolean onNavigationItemSelected(@NonNull MenuItem item) {
        switch (item.getItemId()) {
            case R.id.action_first:
                viewPager.setCurrentItem(0, false);
                break;
            case R.id.action_second:
                viewPager.setCurrentItem(1, false);
                break;
            case R.id.action_third:
                return false;
            case R.id.action_fourth:
                viewPager.setCurrentItem(3, false);
                break;
            case R.id.action_fifth:
                viewPager.setCurrentItem(4, false);
                break;
            default:
                break;
        }

        return true;
    }

    private static class BottomNavigationViewPagerAdapter extends FragmentStateAdapter {
        public BottomNavigationViewPagerAdapter(FragmentActivity fa) {
            super(fa);
        }

        @Override
        public Fragment createFragment(int position) {
            switch (position) {
                case 0:
                    return new FirstPageFragment();
                case 1:
                    return new SecondPageFragment();
                case 2:
                    return new ThirdPageFragment();
                case 3:
                    return new FourthPageFragment();
                case 4:
                    return new FifthPageFragment();
            }

            return null;
        }

        @Override
        public int getItemCount() {
            return NUM_PAGES;
        }
    }

}

And here is the class for the second page in the ViewPager2:

public class SecondPageFragment extends Fragment {

    private MyAdapter myAdapter;

    private LinearLayoutManager layoutManager;

    private RecyclerView recyclerView;

    private EndlessRecyclerViewScrollListener scrollListener;

    private List<Object> objects = new ArrayList<>();

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

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

        recyclerView = view.findViewById(R.id.recycler_view);

        layoutManager = new LinearLayoutManager(getContext());
        recyclerView.setLayoutManager(layoutManager);

        myAdapter = new MyAdapter(getContext(), layoutManager, objects);
        recyclerView.setAdapter(myAdapter);

        scrollListener = new EndlessRecyclerViewScrollListener(layoutManager) {
            @Override
            public void onLoadMore(int page, int totalItemsCount, RecyclerView view) {
                getData(page);
            }
        };
        recyclerView.addOnScrollListener(scrollListener);
    }

    private void getData(final int page) {
        // Here I call the API to fetch the data and add them to the objects list
    }
}

Why is it not calling page 2 for the RecyclerView when scrolling in this situation and what can I do to fix it?

Thanks!

2
0

You might be interested in checking your constraints on the ViewPager2 as it hosts the fragment containing the RecyclerView - also the whole structure of this particular fragment(in your XML layouts).

Since both are scrollable, the layout_height and layout_width of the layout hierarchy greatly affect when the events of the recyclerView are triggered, some of them may never reach the event listeners.

In the official documentation for migrating from ViewPager, there's a small note on support for nested scrolling here

ViewPager2 does not natively support nested scroll views in cases where the scroll view has the same orientation as the ViewPager2 object that contains it. For example, scrolling would not work for a vertical scroll view inside a vertically-oriented ViewPager2 object.

With the assumption that your RecyclerView is not using the same orientation with the viewPager, you can run your fragment on its own and debug to determine if onLoadMore is actually being triggered when not in a viewPager context/container.

As a side note, find some time to read on Paging3 and beyond.

2021-11-24 07:44:35

The RecyclerView is in fact using the same orientation as the ViewPager, both are vertical.
user1695123

0

I ended up fixing this by just using a different infinite scroll RecyclerView class:

https://stackoverflow.com/a/26561717/14968122

2021-12-03 17:41:04

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