A CND, or click-and-drag, is a trio of functions that forms an interface to click-and-drag code functions. The three methods are.
CND或Click - and - Drag，是由3个函数组成的一个组合，它形成了点击-拖动函数的一个接口。
2
Each click-anddrag operation ends with the release of the mouse button, at which point you want to remove all the handlers you installed at the beginning of the click-and-drag operation.
每个点击-拖动操作最后都是释放鼠标按钮，此时您希望移除在点击-拖放操作开始时安装的所有处理程序。
3
Clickanddrag the incoming arrow from the element to an empty diagram location.