iphone開(kāi)發(fā)之解決viewWillAppear失效

你可曾遇到過(guò)viewWillAppear沒(méi)有被調(diào)用到的情況

產(chǎn)生原因是用了UINavigationController. 
將UINavigationController的view作為subview添加到了其他viewController的view中。
或者把UINavigationController添加到UITabbarController中了。

此時(shí)，NavigationController的stack里面的viewController就收不到-(void)viewWillAppear:(BOOL)animated；等4個(gè)方法的調(diào)用。

原因呢

Apple Docs state:

Warning: If the view belonging to a view controller is added to a view hierarchy directly, the view controller will not receive this message. If you insert or add a view to the view hierarchy, and it has a view controller, you should send the associated view controller this message directly. Failing to send the view controller this message will prevent any associated animation from being displayed.

不過(guò)后面的到4.0的文檔就沒(méi)有發(fā)現(xiàn)這樣的文字描述了，但是還是沒(méi)能夠調(diào)用的到這樣

只是添加的更復(fù)雜的文檔，頭暈暈看不下去了。

解決方法兩種：
1，在導(dǎo)航控制器上層controller的viewWillAppear中顯式調(diào)用viewWillAppear方法。

-(void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated]; [subNavCntlr viewWillAppear:animated];
}

- (void)viewWillDisappear:(BOOL)animated
{
[super viewWillDisappear:animated];
[subNavCntlr viewWillDisappear:animated];
}

2，把導(dǎo)航控制器上層controller設(shè)為UINavigationController的delegate

nav.delegate = self;

@interface RootViewController : UIViewController <UINavigationControllerDelegate> { UINavigationController *navController; }

- (void )navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL )animated { [viewController viewWillAppear:animated]; } - (void )navigationController:(UINavigationController *)navigationController didShowViewController:(UIViewController *)viewController animated:(BOOL )animated { [viewController viewDidAppear:animated]; }

湊合著用吧，我喜歡第二種，不過(guò)我更喜歡干脆不再viewWillappear里做事情了。