UITabBar从代理隐藏时观察

Question

如何在隐藏UITabBar的时候添加观察器（通过'hides-bottom-bar-when-pushing'）？我有一个自定义按钮，位于我的标签栏下方，我想确保它在隐藏UITabBar时不会出现。谢谢！

Answer 1

的最好的选择是把你的UIToolbar在启用了剪辑的UIView中，并将剪辑视图放置在UITabBar的上方。然后添加这个UIView作为您的UITabBar的子视图。这种方式显示和隐藏UITabBar将自动显示或隐藏您的UIToolbar现在您可以动画显示和隐藏您的UIToolbar，并且每次UITabBar时仍然会消失。

Answer 2

尝试使用UINavigationControllerDelegate protocol：

- (void)navigationController:(UINavigationController *)navigationController 
     willShowViewController:(UIViewController *)viewController 
        animated:(BOOL)animated 
{ 
    if (viewController.hidesBottomBarWhenPushed) { 
     // ... 
    } 
} 

Answer 3

这会告诉你的时候该字段的值更改：

UITabBar *myTabBar = [[UITabBar alloc] init]; 

[self addObserver:myInterestedObjectWhoWantsToKnowWhenTabBarHiddenChanges 
     forKeyPath:@"myTabBar.hidesBottomBarWhenPushed" 
      options:NSKeyValueObservingOptionNew 
      context:nil]; 

然后在myInterestedObjectWhoWantsToKnowWhenTabBarHiddenChanges.m，实现

 - (void)observeValueForKeyPath:(NSString *)keyPath 
        ofObject:(id)object 
        change:(NSDictionary *)change 
        context:(void *)context {  

       if ([keyPath isEqualToString:@"myTabBar.hidesBottomBarWhenPushed"]) { // this key must match, where observer is set.   
        // object will be "self" from the code above 
        // and the change dictionary will have the old and new values. 
       } 
     }