objective-c - iOS-UIAlertView被提前解雇

我有一个视图，上面还有一个按钮。当用户按下按钮时，将执行以下代码:

- (IBAction) goToPhotoViewControllerView:(id) sender{

    alert = [[UIAlertView alloc] initWithTitle:@"Por favor, aguarde" message:@"Carregando imagens"
                                  delegate:nil
                         cancelButtonTitle:nil
                         otherButtonTitles:nil];
    [alert show];

    if(alert != nil) {
        UIActivityIndicatorView *indicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];

        indicator.center = CGPointMake(alert.bounds.size.width/2, alert.bounds.size.height-45);
        [indicator startAnimating];
        [alert addSubview:indicator];
        [indicator release];
    }

    dispatch_async(dispatch_get_global_queue(0, 0), ^{

    //Do a lot of stuff here

        PhotoViewController *photoViewControllerView = [[PhotoViewController alloc] initWithNibName:@"PhotoViewController" bundle:nil];

        [iosDao selectComics];

        [photoViewControllerView startWithComic:[[iosDao.comics lastObject] idComic] numPanels:[[[iosDao.comics lastObject] panels] count]];
        photoViewControllerView.navigationItem.title = @"Comics";

        [iosDao release];
        [[self navigationController] pushViewController:photoViewControllerView animated:YES];

        [alert dismissWithClickedButtonIndex:0 animated:YES];
        [alert release];
    });
}

发生的情况是，在大多数情况下，整个异步代码都会运行，从而消除警报消息。但是，在消除警报消息后，在将屏幕推送到下一个viewController(photoViewControllerView)之前，屏幕仍保持冻结状态约2或3秒。我不知道为什么会这样。我希望警报消息能够根据需要持续存在。有任何想法吗？

先感谢您!

最佳答案

对我来说，这听起来像是问题在于PhotoViewController需要花费一些时间来加载(您可以使用Instruments进行确认吗？)。由于PhotoViewController是您自己的类，因此您可以让它有一个委托，使主视图控制器(消除UIAlert的那个)成为PhotoViewController实例的委托，并让PhotoViewController调用委托以在准备就绪时通知它和/或可见，例如在

- (void)viewWillAppear:(BOOL)animated