objective-c - iOS - UIAlertView 在预期之前被关闭

Question

我有一个 View ，其中还有一个按钮。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];
    });
}

实际情况是，大多数时候，整个异步代码都在运行，并消除了警报消息。但是，在警报消息消失后​​，屏幕在推送到下一个 viewController (photoViewControllerView) 之前仍会卡住大约 2 或 3 秒。我不知道为什么会这样。我希望警报消息在需要时一直显示。有什么想法吗？

提前致谢!

Answer 1

所以对我来说，听起来问题是 PhotoViewController 需要时间来加载(您可以使用 Instruments 来确认吗？)。由于 PhotoViewController 是你自己的类，你可以让它有一个委托(delegate)，使主视图 Controller (解除 UIAlert 的那个)成为 PhotoViewController 实例的委托(delegate)，并让 PhotoViewController 在准备好和/或时调用委托(delegate)通知它可见，例如在

的末尾

- (void)viewWillAppear:(BOOL)animated