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我改变了我的旧的NSthread，因为无法从后台线程更新 UI。现在我正在使用dispatch_async.

问题是当此代码第二次执行时，在 ApplicationDidBecomeActive 中（当用户隐藏并再次显示应用程序时）永远不要退出那个同时，保持无限循环。

这里我展示了关于dispatch_async的新代码，NSURLConnection代码一直有效，最后恢复...我认为问题不存在

- (void)applicationDidBecomeActive:(UIApplication *)application
   {    

     //  first connection to the server through NSURLConnection, downloading a json list
     [wsDataVideos getVideosData:URL_WS_VIDEOS];

     dispatch_queue_t secondDownloadQueue = dispatch_queue_create("name",NULL);            
     dispatch_async(secondDownloadQueue, ^{

           // wait for wsDataVideos has finished. IT SEEMS THIS COLLAPSES CPU ¿?
           while (wsDataVideos.imported==NO) {}

          // If are there new videos begins sincronous and slower download:
          if ....{

             dispatch_async(dispatch_get_main_queue(), ^{
                // Update the UI: inform user begins download
                [menuViewController.badgeVideos setBadgeVideosText:@"Downloading..."];
                 });

             // Download videos (sincro)

             dispatch_async(dispatch_get_main_queue(), ^{
                 // informs user is completed
                 [menuViewController.badgeVideos setBadgeVideosText:@"Downloaded"];
                 });
           } 
        });

    }

第一个连接（json），而不是我在那个时候等待：

-(void)getVideosData:(NSString *)url_ws{

    NSLog(@"Get videos data1 ");

    if  (wsData){
        [wsData setLength:0];
    }
    else{
        wsData=[[NSMutableData alloc] init];
    }

    NSURLRequest *reqCat=[NSURLRequest requestWithURL:[NSURL URLWithString:url_ws] cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60.0];
    NSURLConnection *conCat=[[NSURLConnection alloc] initWithRequest:reqCat delegate:self];

}

用他们的方法：

-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{
...
-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{
    [wsData    appendData:data];
}

...
-(void)connectionDidFinishLoading:(NSURLConnection *)connection{
...

有任何想法吗？再次感谢。

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1 回答 1

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如果我在 while{} 中放入代码，它可以工作，但我认为这很奇怪..chunk，糟糕的代码，不是吗？也许更好的解决方案类似于 dispatch_group_wait() ？

   // wait for wsDataVideos has finished. IT SEEMS THIS COLLAPSES CPU ¿?
   while (wsDataVideos.imported==NO) {
        sleep(1)
  }
于 2013-10-25T13:59:04.490 回答