ios - ios:UIAlertView在for循环执行之前立即显示

Question

我有以下代码:

 UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Loading Content For the First Time..."
                                                   message:@"\n"
                                                  delegate:self
                                         cancelButtonTitle:nil
                                         otherButtonTitles:nil];

            UIActivityIndicatorView *spinner = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];
            spinner.center = CGPointMake(139.5, 75.5); // .5 so it doesn't blur
            [alertView addSubview:spinner];
            [spinner startAnimating];
            [alertView show];

            for (TCMLevelRemote *level in [obj objectForKey:@"levels"]){
                [[TCMExhibitFeedStore sharedStore] createLevel:level];
            }
            [[TCMExhibitFeedStore sharedStore] loadAllLevels];
            [[TCMExhibitFeedStore sharedStore] setAllLevels:[[TCMExhibitFeedStore sharedStore] storedLevels]];
            [alertView dismissWithClickedButtonIndex:0 animated:YES];

for循环需要一段时间才能执行，因为它会在应用程序首次运行时下载一些信息。因此，我希望显示该通知，以便用户不会坐在无响应的屏幕上等待。问题是直到for循环结束后才显示alertview。然后它就马上消失了。我需要更改什么？

Answer 1

在 .h 类中声明您的alert-view对象，以便在 .m 类中的任何地方使用。

将for循环代码放入performSelectorInBackground中，以便在Backgroud中运行循环，这样您Alertview就不必等待ForLoop完成了。

 [self performSelectorInBackground: @selector(LoadForLoop) withObject: nil];

-(void)LoadForLoop
{
 for (TCMLevelRemote *level in [obj objectForKey:@"levels"]){
                [[TCMExhibitFeedStore sharedStore] createLevel:level];
            }
            [[TCMExhibitFeedStore sharedStore] loadAllLevels];
            [[TCMExhibitFeedStore sharedStore] setAllLevels:[[TCMExhibitFeedStore sharedStore] storedLevels]];
            [alertView dismissWithClickedButtonIndex:0 animated:YES];

}

其他解决方案

您还可以按照您的代码像波纹管一样使用Grand Central Dispatch (GCD):-

UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Loading Content For the First Time..."
                                                   message:@"\n"
                                                  delegate:self
                                         cancelButtonTitle:nil
                                         otherButtonTitles:nil];

            UIActivityIndicatorView *spinner = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];
            spinner.center = CGPointMake(139.5, 75.5); // .5 so it doesn't blur
            [alertView addSubview:spinner];
            [spinner startAnimating];
            [alertView show];



dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
          for (TCMLevelRemote *level in [obj objectForKey:@"levels"]){
                [[TCMExhibitFeedStore sharedStore] createLevel:level];
            }
            [[TCMExhibitFeedStore sharedStore] loadAllLevels];
            [[TCMExhibitFeedStore sharedStore] setAllLevels:[[TCMExhibitFeedStore sharedStore] storedLevels]];

        dispatch_async(dispatch_get_main_queue(), ^{
            [spinner StopAnimating];
            [alertView dismissWithClickedButtonIndex:0 animated:YES];
        });
    });