打印調用的順序:
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:]
先調用試圖控制器的viewWillLayoutSubviews 以及viewDidLayoutSubviews,然后調用view的layoutSubviews、layoutSubviews 。最后調用drawRect