控制器布局的生命周期

打印调用的顺序：

TestFunctionCall[49445:60b] ---> -[ZQRootViewController viewDidLoad]

TestFunctionCall[49445:60b] ---> -[ZQCustomView initWithFrame:]

TestFunctionCall[49445:60b] ---> -[ZQRootViewControllerview WillLayoutSubviews]

TestFunctionCall[49445:60b] ---> -[ZQRootViewControllerview DidLayoutSubviews]

TestFunctionCall[49445:60b] ---> -[ZQCustomView layoutSubviews]

TestFunctionCall[49445:60b] ---> -[ZQCustomView layoutSubviews]

TestFunctionCall[49445:60b] ---> -[ZQCustomView drawRect:]

先调用试图控制器的viewWillLayoutSubviews 以及viewDidLayoutSubviews，然后调用view的layoutSubviews、layoutSubviews 。最后调用drawRect