(这既是一个问题，也是一个答案，因为要找到真正的答案需要花费相当多的时间.)
症状:我的UIViewController中没有调用viewWillAppearviewDidAppear.
原因:在UIViewController中嵌入UINavigationController或UITabBarController(我的 case )会以某种方式中断对这些方法的调用.
解决方案:在包含上述UINavigationController/UITabBarController的UIViewController中手动调用它们.
例如(假设projectNavigationController是你的UINavigationController):
-(void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
[projectNavigationController viewWillAppear:animated];
}
-(void)viewWillDisappear:(BOOL)animated {
[super viewWillDisappear:animated];
[projectNavigationController viewWillDisappear:animated];
}
-(void)viewDidAppear:(BOOL)animated {
[super viewDidAppear:animated];
[projectNavigationController viewDidAppear:animated];
}
-(void)viewDidDisappear:(BOOL)animated {
[super viewDidDisappear:animated];
[projectNavigationController viewDidDisappear:animated];
}
在我的例子中，我有一个内部UITabBarController，我相应地调用了这些方法，所有问题都解决了.
(解决方案的归属:http://davidebenini.it/2009/01/03/viewwillappear-not-being-called-inside-a-uinavigationcontroller/)