/** *  根据圆心的坐标点、半径、当前手势所在的坐标点，计算出圆的运动轨迹坐标 *  @param radius 圆心半径 *  @param centerCircle 圆心的坐标点 *  @param currentPoint 当前的手势所在的坐标点 *  @return CGPoint 返回圆的坐标 */+(CGPoint)CirclePoint:(CGFloat)radius withCenterCircle:(CGPoint)centerCircle withCurrentPoint:(CGPoint)currentPoint;+(CGPoint)CirclePoint:(CGFloat)radius withCenterCircle:(CGPoint)centerCircle withCurrentPoint:(CGPoint)currentPoint{    CGPoint cPoint;    CGFloat x = currentPoint.x;    CGFloat y = currentPoint.y;    CGFloat cX ; //圆的X坐标轨迹    CGFloat cY ; //圆的Y坐标轨迹    CGFloat daX; // 圆心到转动按钮的距离的平方    //CGFloat daY;    CGFloat aX;  // 圆心到转动按钮的距离    //CGFloat aY;    CGFloat cosX;  // 圆心水平方向与转动按钮形成的夹角的cos值        //圆心与触控点的距离的平方（勾股定理）    daX =  (x - centerCircle.x)*(x - centerCircle.x) + (y - centerCircle.y)*(y - centerCircle.y);    aX = sqrt(daX); //开根号  //圆心与触控点的距离    cosX =  fabs(x - centerCircle.x)/aX;  //绝对值    cX = cosX*radius ; //  x =R * cosX;  圆心到触控点在水平坐标的X的值    cY = sqrt(radius*radius - cX*cX);        if(x<centerCircle.x) //如果X所在的点小于圆心 在圆心的左边    {        cX = centerCircle.x - cX;    }    else    {        cX = centerCircle.x + cX;    }        if(y<centerCircle.y)    {        cY = centerCircle.y - cY;    }    else    {        cY = centerCircle.y + cY;    }    cPoint.x = cX;    cPoint.y = cY;    return cPoint;}