GooView.java 文件源码

/**
     * 通过绘制Path构建一个ShapeDrawable，用来绘制到画布Canvas上
     * @return
     */
    private ShapeDrawable drawGooView() {
        Path path = new Path();


        //1. 根据当前两圆圆心的距离计算出固定圆的半径
        float distance = (float) GeometryUtil.getDistanceBetween2Points(mDragCenter, mStickCenter);
        stickCircleTempRadius = getCurrentRadius(distance);

        //2. 计算出经过两圆圆心连线的垂线的dragLineK（对边比临边）。求出四个交点坐标
        float xDiff = mStickCenter.x - mDragCenter.x;
        Double dragLineK = null;
        if(xDiff != 0){
            dragLineK = (double) ((mStickCenter.y - mDragCenter.y) / xDiff);
        }

            //分别获得经过两圆圆心连线的垂线与圆的交点（两条垂线平行，所以dragLineK相等）。
        PointF[] dragPoints = GeometryUtil.getIntersectionPoints(mDragCenter, dragCircleRadius, dragLineK);
        PointF[] stickPoints = GeometryUtil.getIntersectionPoints(mStickCenter, stickCircleTempRadius, dragLineK);

        //3. 以两圆连线的0.618处作为 贝塞尔曲线 的控制点。（选一个中间点附近的控制点）
        PointF pointByPercent = GeometryUtil.getPointByPercent(mDragCenter, mStickCenter, 0.618f);


        // 绘制两圆连接
        //此处参见示意图{@link https://github.com/PoplarTang/DragGooView }
        path.moveTo((float)stickPoints[0].x, (float)stickPoints[0].y);
        path.quadTo((float)pointByPercent.x, (float)pointByPercent.y,
                (float)dragPoints[0].x, (float)dragPoints[0].y);
        path.lineTo((float)dragPoints[1].x, (float)dragPoints[1].y);
        path.quadTo((float)pointByPercent.x, (float)pointByPercent.y,
                (float)stickPoints[1].x, (float)stickPoints[1].y);
        path.close();

        //将四个交点画到屏幕上
//      path.addCircle((float)dragPoints[0].x, (float)dragPoints[0].y, 5, Direction.CW);
//      path.addCircle((float)dragPoints[1].x, (float)dragPoints[1].y, 5, Direction.CW);
//      path.addCircle((float)stickPoints[0].x, (float)stickPoints[0].y, 5, Direction.CW);
//      path.addCircle((float)stickPoints[1].x, (float)stickPoints[1].y, 5, Direction.CW);

        //构建ShapeDrawable
        ShapeDrawable shapeDrawable = new ShapeDrawable(new PathShape(path, 50f, 50f));
        shapeDrawable.getPaint().setColor(Color.RED);
        return shapeDrawable;
    }