什麼self.view.widow之間的差異，[[UIApplication的sharedApplication] keyWindow]在Objective-C

Question

，如果我不喜歡這個

- (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]; 
} 

然後紅色視圖和警報會後alertView:clickedButtonAtIndex:調用返回自動解除

誰可以告訴我原因嗎？

什麼和[UIApplication的sharedApplication] keyWindow]在Objective-C

Answer 1

你的問題基本上是在此解決self.view.widow之間的區別：

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

爲了配合回你的問題，UIAlertView會出現在系統窗口中，而這個窗口就是顯示警報時的keyWindow。當警報解除時，該窗口消失，因此視圖消失的原因。

假設self.view是應用程序窗口的子視圖（幾乎總是這種情況），您的視圖將繼續顯示，因爲窗口本身在警報解除後繼續顯示。