RecyclerView side slide menu layout processing

public class SlideRecyclerView extends RecyclerView {

/**最小速度*/
private static final int MINIMUM_VELOCITY = 500;

/**滑动的itemView*/
private ViewGroup mMoveView;

/**末次滑动的itemView*/
private ViewGroup mLastView;

/**itemView中菜单控件宽度*/
private int mMenuWidth;

private VelocityTracker mVelocity;

/**触碰时的首个横坐标*/
private int mFirstX;

/**触碰时的首个纵坐标*/
private int mFirstY;

/**触碰末次的横坐标*/
private int mLastX;

/**最小滑动距离*/
private int mTouchSlop;

private Scroller mScroller;

/**是否正在水平滑动*/
private boolean mMoving;


public SlideRecyclerView(Context context) {
    super(context);
    init();
}

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

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

private void init(){
    mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
    mScroller = new Scroller(getContext());
}

@Override
public boolean onInterceptTouchEvent(MotionEvent e) {
    int x = (int) e.getX();
    int y = (int) e.getY();
    addVelocityEvent(e);
    switch (e.getAction()){
        case MotionEvent.ACTION_DOWN:
            //若Scroller处于动画中，则终止动画
            if (!mScroller.isFinished()){
                mScroller.abortAnimation();
            }
            mFirstX = x;
            mFirstY = y;
            mLastX = x;
            //获取点击区域所在的itemView
            mMoveView = (ViewGroup) findChildViewUnder(x, y);
            //在点击区域以外的itemView开着菜单，则关闭菜单
            if (mLastView != null && mLastView != mMoveView && mLastView.getScrollX() != 0){
                closeMenu();
            }
            //获取itemView中菜单的宽度（规定itemView中为两个子View）
            if (mMoveView != null && mMoveView.getChildCount() == 2){
                mMenuWidth = mMoveView.getChildAt(1).getWidth();
            }else {
                mMenuWidth = -1;
            }
            break;
        case MotionEvent.ACTION_MOVE:
            mVelocity.computeCurrentVelocity(1000);
            int velocityX = (int) Math.abs(mVelocity.getXVelocity());
            int velocityY = (int) Math.abs(mVelocity.getYVelocity());
            int moveX = Math.abs(x - mFirstX);
            int moveY = Math.abs(y - mFirstY);
            //满足如下条件其一则判定为水平滑动：
            //1、水平速度大于竖直速度,且水平速度大于最小速度
            //2、水平位移大于竖直位移,且大于最小移动距离
            //必需条件：itemView菜单栏宽度大于0，且recyclerView处于静止状态（即并不在竖直滑动和拖拽）
            boolean isHorizontalMove = (Math.abs(velocityX) >= MINIMUM_VELOCITY && velocityX > velocityY || moveX > moveY
                    && moveX > mTouchSlop) && mMenuWidth > 0 && getScrollState() == 0;
            if (isHorizontalMove){
                //设置其已处于水平滑动状态，并拦截事件
                mMoving = true;
                return true;
            }
            break;
        case MotionEvent.ACTION_UP:
        case MotionEvent.ACTION_CANCEL:
            releaseVelocity();
            //itemView以及其子view触发触碰事件(点击、长按等)，菜单未关闭则直接关闭
            closeMenuNow();
            break;
        default:break;
    }
    return super.onInterceptTouchEvent(e);
}

@Override
public boolean onTouchEvent(MotionEvent e) {
    int x = (int) e.getX();
    int y = (int) e.getY();
    addVelocityEvent(e);
    switch (e.getAction()){
        case MotionEvent.ACTION_DOWN:
            break;
        case MotionEvent.ACTION_MOVE:
            //若已处于水平滑动状态，则随手指滑动，否则进行条件判断
            if (mMoving){
                int dx = mLastX - x;
                //让itemView在规定区域随手指移动
                if (mMoveView.getScrollX() + dx >= 0 && mMoveView.getScrollX() + dx <= mMenuWidth) {
                    mMoveView.scrollBy(dx, 0);
                }
                mLastX = x;
                return true;
            }else {
                mVelocity.computeCurrentVelocity(1000);
                int velocityX = (int) Math.abs(mVelocity.getXVelocity());
                int velocityY = (int) Math.abs(mVelocity.getYVelocity());
                int moveX = Math.abs(x - mFirstX);
                int moveY = Math.abs(y - mFirstY);
                //根据水平滑动条件判断，是否让itemView跟随手指滑动
                //这里重新判断是避免itemView中不拦截ACTION_DOWN事件，则后续ACTION_MOVE并不会走onInterceptTouchEvent()方法
                boolean isHorizontalMove = (Math.abs(velocityX) >= MINIMUM_VELOCITY && velocityX > velocityY
                        || moveX > moveY && moveX > mTouchSlop) && mMenuWidth > 0 && getScrollState() == 0;
                if (isHorizontalMove) {
                    int dx = mLastX - x;
                    //让itemView在规定区域随手指移动
                    if (mMoveView.getScrollX() + dx >= 0 && mMoveView.getScrollX() + dx <= mMenuWidth) {
                        mMoveView.scrollBy(dx, 0);
                    }
                    mLastX = x;
                    //设置正处于水平滑动状态
                    mMoving = true;
                    return true;
                }
            }
            break;
        case MotionEvent.ACTION_UP:
        case MotionEvent.ACTION_CANCEL:
            if (mMoving) {
                //先前没结束的动画终止，并直接到终点
                if (!mScroller.isFinished()){
                    mScroller.abortAnimation();
                    mLastView.scrollTo(mScroller.getFinalX(),0);
                }
                mMoving = false;
                //已放手，即现滑动的itemView成了末次滑动的itemView
                mLastView = mMoveView;
                mVelocity.computeCurrentVelocity(1000);
                int scrollX = mLastView.getScrollX();
                //若速度大于正方向最小速度，则关闭菜单栏；若速度小于反方向最小速度，则打开菜单栏
                //若速度没到判断条件，则对菜单显示的宽度进行判断打开/关闭菜单
                if (mVelocity.getXVelocity() >= MINIMUM_VELOCITY){
                    mScroller.startScroll(scrollX, 0, -scrollX, 0, Math.abs(scrollX));
                }else if (mVelocity.getXVelocity() <= -MINIMUM_VELOCITY){
                    int dx = mMenuWidth - scrollX;
                    mScroller.startScroll(scrollX, 0, dx, 0, Math.abs(dx));
                } else if (scrollX > mMenuWidth / 2) {
                    int dx = mMenuWidth - scrollX;
                    mScroller.startScroll(scrollX, 0, dx, 0, Math.abs(dx));
                } else {
                    mScroller.startScroll(scrollX, 0, -scrollX, 0, Math.abs(scrollX));
                }
                invalidate();
            } else if (mLastView != null && mLastView.getScrollX() != 0){
                //若不是水平滑动状态，菜单栏开着则关闭
                closeMenu();
            }
            releaseVelocity();
            break;
        default:break;
    }
    return super.onTouchEvent(e);
}


@Override
public void computeScroll() {
    if (mScroller.computeScrollOffset()) {
        if (isInWindow(mLastView)){
            mLastView.scrollTo(mScroller.getCurrX(), 0);
            invalidate();
        }else {
            //若处于动画的itemView滑出屏幕，则终止动画，并让其到达结束点位置
            mScroller.abortAnimation();
            mLastView.scrollTo(mScroller.getFinalX(),0);
        }
    }
}

/**
 * 使用Scroller关闭菜单栏
 */
public void closeMenu(){
    mScroller.startScroll(mLastView.getScrollX(),0, -mLastView.getScrollX(), 0 ,500);
    invalidate();
}

/**
 * 即刻关闭菜单栏
 */
public void closeMenuNow(){
    if (mLastView != null && mLastView.getScrollX() != 0) {
        mLastView.scrollTo(0, 0);
    }
}

/**
 * 获取VelocityTracker实例，并为其添加事件
 * @param e 触碰事件
 */
private void addVelocityEvent(MotionEvent e){
    if (mVelocity == null){
        mVelocity = VelocityTracker.obtain();
    }
    mVelocity.addMovement(e);
}

/**
 * 释放VelocityTracker
 */
private void releaseVelocity(){
    if (mVelocity != null){
        mVelocity.clear();
        mVelocity.recycle();
        mVelocity = null;
    }
}

/**
 * 判断该itemView是否显示在屏幕内
 * @param view itemView
 * @return isInWindow
 */
private boolean isInWindow(View view){
    if (getLayoutManager() instanceof LinearLayoutManager) {
        LinearLayoutManager manager = (LinearLayoutManager) getLayoutManager();
        int firstPosition = manager.findFirstVisibleItemPosition();
        int lastPosition = manager.findLastVisibleItemPosition();
        int currentPosition = manager.getPosition(view);
        return currentPosition >= firstPosition && currentPosition <= lastPosition;
    }
    return true;
}
Copy the code

}