让viewDidAppear/viewWillAppear 在页面加载前始终调用

viewDidAppear、viewWillAppear in UINavigationController not be called

When you push or pop a view controller on/off a navigaction controller's stack, the usual viewWillAppear / viewDidappear methods aren't called. If you want to ensure they're always called, just add the UINavigationControllerDelegate protocol to your root view controller:

 1 @interface RootViewController : UIViewController <UINavigationControllerDelegate> {
 2 UINavigationController *navController;
 3 }
 4 
 5 Then implement these two methods:
 6 - (void)navigationController:(UINavigationController *)navigationController 
 7 willShowViewController:(UIViewController *)viewController animated:(BOOL)animated 
 8 {
 9 [viewController viewWillAppear:animated];
10 }
11 
12 - (void)navigationController:(UINavigationController *)navigationController 
13 didShowViewController:(UIViewController *)viewController animated:(BOOL)animated 
14 {
15 [viewController viewDidAppear:animated];
16 }

Be sure to set the root view controller as the delegate for the nav controller. Now viewWillAppear / viewDidAappear will be called whenever a controller is pushed/popped from the stack.

If you want to call the viewWillDisappear/viewDidDisappear methods, your view controller still has to do that manually before popping itself off the nav stack.

转载于:https://www.cnblogs.com/w-zhijun/archive/2012/05/14/2499076.html