UIBezierPath-Indicator-Windmill. 使用UIBezierPath（贝塞尔路径）画出的指示器、风车，可根据给出的数值指示到对应的角度或转的快慢，均带有动画。 Use UIBezierPath to draw the indicator and windmill, according to the value is given to indicate to a corresponding angle or the speed of rotation, both with animation.