ios:UIAlertView在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第一次运行时下载一些信息.因此,我希望此通知显示,以便用户不会坐在无响应的屏幕上等待.问题是在for循环结束之前,alertview不会显示.然后它马上就消失了.我需要改变什么？

Answer 1

alert-view在.h类中声明您的Object,以便在.m类中使用.

将您的for循环代码放入performSelectorInBackgroundBackgroud 中 的运行循环中,这样您就可以不等待ForLoop的完成了.

 [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];

}

其他方案

您也可以根据您的代码使用Grand Central Dispatch(GCD),如下所示: -

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];
        });
    });