Android应用开发—RecyclerView绘制蒙层

背景：如何在跨越两个或两个以上的item绘制一个view，该view需要跟随recyclerView的滑动而整体移动。

 @Override    public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {        super.onDrawOver(c, parent, state);        final View child = parent.getChildAt(1);        if (child != null) {            final int left = child.getLeft();            final int right = child.getRight();            final int top = child.getTop();            final int bottom = child.getBottom();            int rightV = (right - left) / 6;            int leftV = (right - rightV) - VAUtils.dip2px(mContext, 225);            int topV = bottom - VAUtils.dip2px(mContext, 16);            int bottomV = topV + VAUtils.dip2px(mContext, 82);            ViewGroup.MarginLayoutParams margin = new ViewGroup.MarginLayoutParams(mImageView.getLayoutParams());            margin.setMargins(leftV, topV, rightV, bottomV);            RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(margin);            mImageView.setLayoutParams(layoutParams);            if (!imageClicked) {                mImageView.setVisibility(View.VISIBLE);            }            //画笔            final Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);            //圆心 x 坐标            final float x = parent.getWidth() / 2 + left;            ////圆心 y 坐标            final float y = 100 + top;            //半径            final float radius = 100;            //渐变着色器 坐标随意设置的            final LinearGradient shader = new LinearGradient(x-50, 0, x+100, 200, Color.RED, Color.YELLOW, Shader.TileMode.REPEAT);            paint.setShader(shader);            //绘制圆            c.drawCircle(x, y, radius, paint);        }    }

@Overridepublic void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {    super.onDrawOver(c, parent, state);    //画笔    final Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);    //圆心 x 坐标    final float x = parent.getWidth() / 2;    ////圆心 y 坐标    final float y = 100;    //半径    final float radius = 100;    //渐变着色器 坐标随意设置的    final LinearGradient shader = new LinearGradient(x-50, 0, x+100, 200, Color.RED, Color.YELLOW, Shader.TileMode.REPEAT);    paint.setShader(shader);    //绘制圆    c.drawCircle(x, y, radius, paint);}