Recyclerview Бесконечная прокрутка в обоих направлениях

Question

У меня есть Recyclerview, который загружает бесконечный контент в одном направлении (прокрутка вниз)

Это работает нормально, но сейчас я пытаюсь загрузить бесконечный контент также в другом направлении (прокрутка вверх)

Мой подход был такой:

Фрагмент:

  public class MonthlyFragment extends Fragment {

    List<DayObject> dayObjects = new ArrayList<DayObject>();

    List<DayObject> beforeDayObjects = new ArrayList<DayObject>();

    RecyclerView recyclerView;

    ViewModel viewModel;

    CustomAdapter = new CustomAdapter();

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_layout, container, false);
    }

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

        recyclerView = getActivity().findViewById(R.id.recyclerview);

        GridLayoutManager gridLayoutManager = new GridLayoutManager(getContext(), 7);

        viewModel = ViewModelProviders.of(getActivity()).get(ViewModel.class);

        recyclerView.setLayoutManager(gridLayoutManager);
        recyclerView.setHasFixedSize(false);
        recyclerView.setAdapter(adapter);

        scrollListener = new EndlessRecyclerViewScrollListener(gridLayoutManager) {
            @Override
            public void onLoadMore(int page, int totalItemsCount, RecyclerView view) {

                generateData()
            }
            @Override
            public void onLoadMoreBeginning() {

                generateDataBefore();
            }
        };
        recyclerView.addOnScrollListener(scrollListener);

    }

    public void generateData(){

       dayObjects = ...; // generating data

        adapter.submitList(dayObjects);
        adapter.notifyDataSetChanged();

        //working as expected
    }

    public void generateDataBefore(){

      beforeDayObjects = ...; //generating data

        dayObjects = Stream.concat(beforeDayObjects.stream(), dayObjects.stream())
                .collect(Collectors.toList());

        beforeDayObjects.removeAll(beforeDayObjects);

        adapter.submitList(dayObjects);
        adapter.notifyDataSetChanged();

        //not working 
    }
}

EndlessRecyclerViewScrollListener:

    public abstract class EndlessRecyclerViewScrollListener extends RecyclerView.OnScrollListener {

    private int visibleThreshold = 7;

    private int currentPage = 0;

    private int previousTotalItemCount = 0;
    private boolean loading = true;
    private int startingPageIndex = 0;

    RecyclerView.LayoutManager mLayoutManager;

 public EndlessRecyclerViewScrollListener(LinearLayoutManager layoutManager) {
        this.mLayoutManager = layoutManager;
    }



    public EndlessRecyclerViewScrollListener(GridLayoutManager layoutManager) {
        this.mLayoutManager = layoutManager;
        visibleThreshold = visibleThreshold * layoutManager.getSpanCount();
    }

    public EndlessRecyclerViewScrollListener(StaggeredGridLayoutManager layoutManager) {
        this.mLayoutManager = layoutManager;
        visibleThreshold = visibleThreshold * layoutManager.getSpanCount();
    }

    public int getLastVisibleItem(int[] lastVisibleItemPositions) {
        int maxSize = 0;
        for (int i = 0; i < lastVisibleItemPositions.length; i++) {
            if (i == 0) {
                maxSize = lastVisibleItemPositions[i];
            }
            else if (lastVisibleItemPositions[i] > maxSize) {
                maxSize = lastVisibleItemPositions[i];
            }
        }
        return maxSize;
    }


    @Override
    public void onScrolled(RecyclerView view, int dx, int dy) {



        if (loading && (totalItemCount > previousTotalItemCount)) {
            loading = false;
            previousTotalItemCount = totalItemCount;
        }

        if (!loading && (lastVisibleItemPosition + visibleThreshold) > totalItemCount) {

            currentPage++;
            onLoadMore(currentPage, totalItemCount, view);
            loading = true;
        }

        if (!loading && (lastVisibleItemPosition - visibleThreshold) < 7) {

            onLoadMoreBeginning();
            loading = true;
        }

    }

    public void resetState() {
        this.currentPage = this.startingPageIndex;
        this.previousTotalItemCount = 0;
        this.loading = true;
    }

    public abstract void onLoadMore(int page, int totalItemsCount, RecyclerView view);

    public abstract void onLoadMoreBeginning();

}

Когда я пробую этот код, я всегда получаю: FATAL EXCEPTION: pool- 1-thread-1

Кто-нибудь знает решение для этого?