横向的scrollView 中，是一个横向的recyclerView A， recyclerView A的item是竖向的recyclerViewB， 如何让scrollView 以及 recyclerView处理两根手指的滑动事件

实现ScrollView和RecyclerView的多指手势处理可以通过继承ScrollView和RecyclerView来实现。

首先，我们需要自定义一个类来继承ScrollView，并重写onInterceptTouchEvent()和onTouchEvent()方法。在onInterceptTouchEvent()方法中判断是否有多指触摸事件，并返回true，拦截ScrollView的触摸事件。在onTouchEvent()方法中判断是否有多指触摸事件，并将事件分发给子View处理。

代码示例：

public class MultiGestureScrollView extends ScrollView {
    private int mActivePointerId = -1;
    private int mLastMotionX;
    private int mLastMotionY;

    public MultiGestureScrollView(Context context) {
        super(context);
    }

    public MultiGestureScrollView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public MultiGestureScrollView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        if (ev.getActionMasked() == MotionEvent.ACTION_DOWN) {
            mActivePointerId = ev.getPointerId(0);
            mLastMotionX = (int) ev.getX();
            mLastMotionY = (int) ev.getY();
        } else if (ev.getActionMasked() == MotionEvent.ACTION_POINTER_DOWN) {
            return true;
        }

        return super.onInterceptTouchEvent(ev);
    }

    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        switch (ev.getActionMasked()) {
            case MotionEvent.ACTION_DOWN:
                mActivePointerId = ev.getPointerId(0);
                mLastMotionX = (int) ev.getX();
                mLastMotionY = (int) ev.getY();
                break;
            case MotionEvent.ACTION_POINTER_DOWN:
                return true;
            case MotionEvent.ACTION_MOVE:
                final int activePointerIndex = ev.findPointerIndex(mActivePointerId);
                final int x = (int) ev.getX(activePointerIndex);
                final int y = (int) ev.getY(activePointerIndex);
                final int deltaX = mLastMotionX - x;
                final int deltaY = mLastMotionY - y;

                if (Math.abs(deltaX) > Math.abs(deltaY)) {
                    // 横向滑动
                    getParent().requestDisallowInterceptTouchEvent(true);
                    super.onTouchEvent(ev);
                    return true;
                } else {
                    // 竖向滑动
                    getParent().requestDisallowInterceptTouchEvent(false);
                    return super.onTouchEvent(ev);
                }
            case MotionEvent.ACTION_UP:
            case MotionEvent.ACTION_CANCEL:
                mActivePointerId = -1;
                break;
        }

        return super.onTouchEvent(ev);
    }
}

接下来，我们需要自定义一个类来继承RecyclerView，并重写onInterceptTouchEvent()和onTouchEvent()方法，实现多指手势处理。在onInterceptTouchEvent()方法中判断是否有多指触摸事件，并返回true，拦截RecyclerView的触摸事件。在onTouchEvent()方法中判断是否有多指触摸事件，并将事件分发给子View处理。

代码示例：

public class MultiGestureRecyclerView extends RecyclerView {
    private int mActivePointerId = -1;
    private int mLastMotionX;
    private int mLastMotionY;

    public MultiGestureRecyclerView(Context context) {
        super(context);
    }

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

    public MultiGestureRecyclerView(Context context, @Nullable AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        if (ev.getActionMasked() == MotionEvent.ACTION_DOWN) {
            mActivePointerId = ev.getPointerId(0);
            mLastMotionX = (int) ev.getX();
            mLastMotionY = (int) ev.getY();
        } else if (ev.getActionMasked() == MotionEvent.ACTION_POINTER_DOWN) {
            return true;
        }

        return super.onInterceptTouchEvent(ev);
    }

    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        switch (ev.getActionMasked()) {
            case MotionEvent.ACTION_DOWN:
                mActivePointerId = ev.getPointerId(0);
                mLastMotionX = (int) ev.getX();
                mLastMotionY = (int) ev.getY();
                break;
            case MotionEvent.ACTION_POINTER_DOWN:
                return true;
            case MotionEvent.ACTION_MOVE:
                final int activePointerIndex = ev.findPointerIndex(mActivePointerId);
                final int x = (int) ev.getX(activePointerIndex);
                final int y = (int) ev.getY(activePointerIndex);
                final int deltaX = mLastMotionX - x;
                final int deltaY = mLastMotionY - y;

                if (Math.abs(deltaX) > Math.abs(deltaY)) {
                    // 横向滑动
                    getParent().requestDisallowInterceptTouchEvent(true);
                    super.onTouchEvent(ev);
                    return true;
                } else {
                    // 竖向滑动
                    getParent().requestDisallowInterceptTouchEvent(false);
                    return super.onTouchEvent(ev);
                }
            case MotionEvent.ACTION_UP:
            case MotionEvent.ACTION_CANCEL:
                mActivePointerId = -1;
                break;
        }

        return super.onTouchEvent(ev);
    }
}

最后，我们将自定义的MultiGestureRecyclerView作为横向的RecyclerView A的布局管理器，并将MultiGestureScrollView包裹横向的RecyclerView A。

代码示例：

<com.example.MultiGestureScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent">

    <androidx.recyclerview.widget.RecyclerView
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="horizontal"
            app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
            app:recycledViewPool="@{recycledViewPool}"
            tools:listitem="@layout/item_horizontal_recycler_view">

        <com.example.MultiGestureRecyclerView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:orientation="vertical"
                app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
                app:recycledViewPool="@{recycledViewPool}"
                tools:listitem="@layout/item_vertical_recycler_view"/>

    </androidx.recyclerview.widget.RecyclerView>

</com.example.MultiGestureScrollView>