Utility class to enforce a single scroll direction for a RecyclerView or a ViewPager2

RecyclerViewUtils.java

package be.digitalia.samples.utils;

import android.view.MotionEvent;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
import androidx.viewpager2.widget.ViewPager2;

public class RecyclerViewUtils {

	@NonNull
	public static RecyclerView getRecyclerView(@NonNull ViewPager2 viewPager) {
		return (RecyclerView) viewPager.getChildAt(0);
	}

	public static void enforceSingleScrollDirection(@NonNull RecyclerView recyclerView) {
		final SingleScrollDirectionEnforcer enforcer = new SingleScrollDirectionEnforcer();
		recyclerView.addOnItemTouchListener(enforcer);
		recyclerView.addOnScrollListener(enforcer);
	}

	private static class SingleScrollDirectionEnforcer extends RecyclerView.OnScrollListener
			implements RecyclerView.OnItemTouchListener {

		private int scrollState = RecyclerView.SCROLL_STATE_IDLE;
		private int scrollPointerId = -1;
		private int initialTouchX;
		private int initialTouchY;
		private int dx;
		private int dy;

		@Override
		public boolean onInterceptTouchEvent(@NonNull RecyclerView rv, @NonNull MotionEvent e) {
			final int action = e.getActionMasked();
			switch (action) {
				case MotionEvent.ACTION_DOWN:
					scrollPointerId = e.getPointerId(0);
					initialTouchX = (int) (e.getX() + 0.5f);
					initialTouchY = (int) (e.getY() + 0.5f);
					break;

				case MotionEvent.ACTION_POINTER_DOWN:
					final int actionIndex = e.getActionIndex();
					scrollPointerId = e.getPointerId(actionIndex);
					initialTouchX = (int) (e.getX(actionIndex) + 0.5f);
					initialTouchY = (int) (e.getY(actionIndex) + 0.5f);
					break;

				case MotionEvent.ACTION_MOVE: {
					final int index = e.findPointerIndex(scrollPointerId);
					if (index >= 0 && scrollState != RecyclerView.SCROLL_STATE_DRAGGING) {
						final int x = (int) (e.getX(index) + 0.5f);
						final int y = (int) (e.getY(index) + 0.5f);
						dx = x - initialTouchX;
						dy = y - initialTouchY;
					}
				}
			}
			return false;
		}

		@Override
		public void onTouchEvent(@NonNull RecyclerView rv, @NonNull MotionEvent e) {
		}

		@Override
		public void onRequestDisallowInterceptTouchEvent(boolean disallowIntercept) {
		}

		@Override
		public void onScrollStateChanged(@NonNull RecyclerView recyclerView, int newState) {
			int oldState = scrollState;
			scrollState = newState;
			if (oldState == RecyclerView.SCROLL_STATE_IDLE && newState == RecyclerView.SCROLL_STATE_DRAGGING) {
				final RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
				if (layoutManager != null) {
					final boolean canScrollHorizontally = layoutManager.canScrollHorizontally();
					final boolean canScrollVertically = layoutManager.canScrollVertically();
					if (canScrollHorizontally != canScrollVertically) {
						if (canScrollHorizontally && Math.abs(dy) > Math.abs(dx)) {
							recyclerView.stopScroll();
						}
						if (canScrollVertically && Math.abs(dx) > Math.abs(dy)) {
							recyclerView.stopScroll();
						}
					}
				}
			}
		}
	}
}

@cbeyls Thanks your code :)
Can I use your code in my commercial app?
Please let me know how I can use the code for commercial distribution.

@seyoung-hyun Indeed I should probably add an explicit license at the top of the code. My intent was to make it available under the MIT License, allowing the use of it in commercial software. Feel free to use it in such software.