锚点(参考 https://www.cnblogs.com/ybw123321/p/5394408.html)
视图的平移、翻转都是以锚点为中心进行,所以希望达到向某个点
实例可以参考:https://github.com/LynnCheng/DropdownMenu
iOS动画
Title:iOS动画
Author:Lynn Cheng
Created:2019-07-01, 13:39:18
Updated:2019-07-01, 13:54:48
Full URL:http://lynncheng.github.io/2019/07/01/iOS动画/
License: "CC BY-NC-SA 4.0" Keep Link & Author if Distribute.