ViewDragHelper使用2

https://blog.csdn.net/lmj623565791/article/details/46858663

public class VDHLayout extends LinearLayout
{
    private ViewDragHelper mDragger;

    private View mDragView;
    private View mAutoBackView;
    private View mEdgeTrackerView;

    private Point mAutoBackOriginPos = new Point();

    public VDHLayout(Context context, AttributeSet attrs)
    {
        super(context, attrs);
        mDragger = ViewDragHelper.create(this, 1.0f, new ViewDragHelper.Callback()
        {
            @Override
            public boolean tryCaptureView(View child, int pointerId)
            {
                //mEdgeTrackerView禁止直接移动
                return child == mDragView || child == mAutoBackView;
            }

            /*这个方法控制 水平方向最多能移动到的位置*/
            @Override
            public int clampViewPositionHorizontal(View child, int left, int dx)
            {
                /*左边移动最远的坐标点 已移动view的左边缘为准*/
                int leftPadding = getPaddingLeft();
                /*右边移动最远的横向坐标 已移动view的左边缘为准*/
                int maxRight = getWidth() - getPaddingRight()-child.getWidth();
                int result = Math.min(Math.max(leftPadding,left),maxRight);
                return result;
            }

            /*定义拖动View的垂直方向的移动范围*/
            @Override
            public int clampViewPositionVertical(View child, int top, int dy)
            {
                /*上移动范围 以上边界为准*/
                int topPadding = getPaddingTop();
                /*下移动范围 以上边界为准*/
                int maxBottom = getHeight() - getPaddingBottom()-child.getHeight();
                 top = Math.min(Math.max(topPadding,top),maxBottom);
                return top;
            }


            //手指释放的时候回调
            @Override
            public void onViewReleased(View releasedChild, float xvel, float yvel)
            {
                //mAutoBackView手指释放时可以自动回去
                if (releasedChild == mAutoBackView)
                {
                    mDragger.settleCapturedViewAt(mAutoBackOriginPos.x, mAutoBackOriginPos.y);
                    invalidate();
                }
            }
            /*如果拖动的view 消耗事件 或者设置完不移动 可以重写这两个方法*/
            //在边界拖动时回调
            @Override
            public void onEdgeDragStarted(int edgeFlags, int pointerId)
            {
                mDragger.captureChildView(mEdgeTrackerView, pointerId);
            }

            /*设置childView的横向移动范围*/
            @Override
            public int getViewHorizontalDragRange(@NonNull View child) {
                return getMeasuredWidth();
            }

            /*设置childView 的纵向移动范围*/
            @Override
            public int getViewVerticalDragRange(@NonNull View child) {
                return getMeasuredHeight();
            }
        });
        mDragger.setEdgeTrackingEnabled(ViewDragHelper.EDGE_LEFT|ViewDragHelper.EDGE_RIGHT);
    }


    @Override
    public boolean onInterceptTouchEvent(MotionEvent event)
    {
        return mDragger.shouldInterceptTouchEvent(event);
    }

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

    @Override
    public void computeScroll()
    {
        if(mDragger.continueSettling(true))
        {
            invalidate();
        }
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b)
    {
        super.onLayout(changed, l, t, r, b);

        mAutoBackOriginPos.x = mAutoBackView.getLeft();
        mAutoBackOriginPos.y = mAutoBackView.getTop();
    }

    @Override
    protected void onFinishInflate()
    {
        super.onFinishInflate();

        mDragView = getChildAt(0);
        mAutoBackView = getChildAt(1);
        mEdgeTrackerView = getChildAt(2);
    }
}