UIViewController中声明如下方法:
//加载视图
- (void)loadView;
//将要卸载视图
- (void)viewWillUnload NS_DEPRECATED_IOS(5_0,6_0);
//已经卸载视图
- (void)viewDidUnload NS_DEPRECATED_IOS(3_0,6_0);
//已经加载
- (void)viewDidLoad;
//视图将要显示
- (void)viewWillAppear:(BOOL)animated;
//视图已经显示
- (void)viewDidAppear:(BOOL)animated;
//视图将要隐藏
- (void)viewWillDisappear:(BOOL)animated;
//视图已经隐藏
- (void)viewDidDisappear:(BOOL)animated;
//将要调用layoutSubviews
- (void)viewWillLayoutSubviews NS_AVAILABLE_IOS(5_0);
//已经调用layoutSubviews
- (void)viewDidLayoutSubviews NS_AVAILABLE_IOS(5_0);