动画

• https://www.jianshu.com/p/71f2fa270b9c

• http://www.voidcn.com/article/p-gjcxeuwa-pz.html

• https://my.oschina.net/ozawa4865/blog/714904

• http://liuyanwei.jumppo.com/2015/10/30/iOS-Animation-UIViewAndCoreAnimation.html

• https://blog.csdn.net/taoerit/article/details/78318288

• https://blog.csdn.net/CHENYUFENG1991/article/details/497790

• https://juejin.im/post/5ae28a9b6fb9a07aaa10fa1e

• http://www.hangge.com/blog/cache/detail_664.html

• https://www.jianshu.com/p/d6a7a7f3ad99

• https://www.jianshu.com/p/c33e97b167e9

• https://www.jianshu.com/p/71f2fa270b9c