什么self.view.widow之间的差异，[[UIApplication的sharedApplication] keyWindow]在Objective-C

Question

，如果我不喜欢这个

- (void)viewDidLoad { 
    [super viewDidLoad]; 
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:nil message:@"test" delegate:self cancelButtonTitle:@"ok" otherButtonTitles:nil]; 
    [alert show]; 
} 

// Called when a button is clicked. The red view and alert will be automatically dismissed after this call returns 
- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex { 
    [self showView]; 
} 

// after animation ,this will work fine 
- (void)alertView:(UIAlertView *)alertView didDismissWithButtonIndex:(NSInteger)buttonIndex { 
// [self showView]; 
} 

- (void)showView { 
    // Called when a button is clicked. The view will be automatically dismissed after this call returns 
    UIView *view = [[UIView alloc] init]; 
    view.frame = CGRectMake(0, 0, 200, 200); 
    view.backgroundColor = [UIColor redColor]; 
    view.center = CGPointMake([UIScreen mainScreen].bounds.size.width/2.0f, [UIScreen mainScreen].bounds.size.height/2.0f); 
    // [self.view.window addSubview:view]; //when i use this ,both of the two delegate methods works fine 
    UIWindow *window = [[UIApplication sharedApplication] keyWindow]; 
    [window addSubview:view]; 
} 

然后红色视图和警报会后alertView:clickedButtonAtIndex:调用返回自动解除

谁可以告诉我原因吗？

什么和[UIApplication的sharedApplication] keyWindow]在Objective-C

Answer 1

你的问题基本上是在此解决self.view.widow之间的区别：

diffrence between [[[[UIApplication sharedApplication] delegate] window] and [[UIApplication sharedApplication].keyWindow?

为了配合回你的问题，UIAlertView会出现在系统窗口中，而这个窗口就是显示警报时的keyWindow。当警报解除时，该窗口消失，因此视图消失的原因。

假设self.view是应用程序窗口的子视图（几乎总是这种情况），您的视图将继续显示，因为窗口本身在警报解除后继续显示。