可画带有箭头的弧形功能

可画带有箭头的弧形功能，源码MVArrowOverlays，MVArrowOverlays包含一个可根据半径和给定两点画出一个带箭头的弧形，适用于了解用户首次使用应用的体验，以及用户对界面上控件按钮的特定掌握。 This project includes a class to draw an arrow as an arc of a circle given two points and the radius. This is well suited for first time user experiences in order to focus the attention of the user on a particular control or button.