仿qq侧滑效果

核心类：private ViewDragHelper mViewDragHelper;
参考：Android群英传

public class DragViewGoup extends FrameLayout {
    private ViewDragHelper mViewDragHelper;
    private View mMenuView;
    private View mMainView;
    private int mWidth;

    public DragViewGoup(Context context) {
        super(context);
        initView();
    }

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

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

    @Override
    protected void onFinishInflate() {
        super.onFinishInflate();
        mMenuView = getChildAt(0);
        mMainView = getChildAt(1);
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        mWidth = mMenuView.getMeasuredWidth();
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        return mViewDragHelper.shouldInterceptTouchEvent(ev);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        mViewDragHelper.processTouchEvent(event);
        return true;
    }

    private void initView() {
        mViewDragHelper = ViewDragHelper.create(this, callback);
    }

    private ViewDragHelper.Callback callback =
            new ViewDragHelper.Callback() {
                @Override
                public boolean tryCaptureView(@NonNull View child, int pointerId) {
                    return mMainView == child;
                }

                @Override
                public int clampViewPositionVertical(@NonNull View child, int top, int dy) {
                    return 0;
                }

                @Override
                public int clampViewPositionHorizontal(@NonNull View child, int left, int dx) {
                    //设置只左右滑动
                    return left;
                }

                @Override
                public void onViewReleased(@NonNull View releasedChild, float xvel, float yvel) {
                    super.onViewReleased(releasedChild, xvel, yvel);
                    if (mMainView.getLeft() < 500) {
                        mViewDragHelper.smoothSlideViewTo(mMainView, 0,0);
                        ViewCompat.postInvalidateOnAnimation(DragViewGoup.this);
                    } else {
                        mViewDragHelper.smoothSlideViewTo(mMainView, 300, 0);
                        ViewCompat.postInvalidateOnAnimation(DragViewGoup.this);
                    }
                }
            };

    @Override
    public void computeScroll() {
        if (mViewDragHelper.continueSettling(true)) {
            ViewCompat.postInvalidateOnAnimation(this);
        }
    }
}