UIAlertView在应用程序的最开始：didFinishLaunchingWithOptions：

Question

我在申请一开始就有以下内容：didFinishLaunchingWithOptions：

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{

    UIAlertView * alertView = [[UIAlertView alloc] initWithTitle:@"Reminder:" message:@"foo" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
    [alertView show];
    NSLog(@"%@ is the parent view",[alertView superview]); // prints "(null)"

    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    // Override point for customization after application launch.
    ...
}

并且UIAlertView仍然显示出来。怎么运作？

Answer 1

警报视图显示在他们自己的窗口中。但是直到运行循环有机会运行才会发生这种情况。当您记录警报视图的超级视图时，警报尚未显示，这就是您获得(null)的原因。