一、原因

ViewPager2的内部实现是RecyclerView，当手势横向移动的距离大于touchSlop的时候，就会认定你有横向滑动的手势，进而驱动ViewPager2进行左右滑动

二、解决办法

重写内部嵌套的RecyclerView:

public class RecyclerViewInVP2 extends RecyclerView {

    public RecyclerViewInVP2(@NonNull Context context) {
        super(context);
    }

    public RecyclerViewInVP2(@NonNull Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
    }

    public RecyclerViewInVP2(@NonNull Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    private int startX, startY;

    @Override
    public boolean dispatchTouchEvent(MotionEvent ev) {
        switch (ev.getAction()) {
            case MotionEvent.ACTION_DOWN:
                startX = (int) ev.getX();
                startY = (int) ev.getY();
                getParent().requestDisallowInterceptTouchEvent(true);//告诉viewgroup不要去拦截我
                break;
            case MotionEvent.ACTION_MOVE:
                int endX = (int) ev.getX();
                int endY = (int) ev.getY();
                int disX = Math.abs(endX - startX);
                int disY = Math.abs(endY - startY);
                if (disX > disY) {
                    getParent().requestDisallowInterceptTouchEvent(false);
                } else {
                    getParent().requestDisallowInterceptTouchEvent(true);//下拉的时候是false
                }
                break;
            case MotionEvent.ACTION_UP:
            case MotionEvent.ACTION_CANCEL:
                getParent().requestDisallowInterceptTouchEvent(true);
                break;
        }
        return super.dispatchTouchEvent(ev);
    }
}

从源码层面分析:

viewpager2+recyclerview/nestscrollview滑动冲突问题 - 掘金既然知道了是在action_move过程中是因为dx或dy大于了mTouchSlop，导致viewpager2中拦截了touch事件，所以我们有没有办法让上下滑动列表recyclerview的时候，不去拦截touch事件呢，答案就是通过上面的requestDisallowInt…https://juejin.cn/post/6886037403413250062