Question

我已更改旧的NSthread，因为无法从后台线程更新UI。现在我正在使用dispatch_async。

问题是当第二次执行此代码时，在ApplicationDidBecomeActive中（当用户隐藏并再次显示应用程序时）从不退出，同时保持无限循环。

在这里，我展示了有关dispatch_async的新代码，NSURLConnection代码始终有效，最后恢复......我不认为问题存在

- (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），比我在那时等待：

-(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{
...

有什么想法吗？再次感谢。

Answer 1

如果我把代码放在{}它可行的情况下，但我认为这是奇怪的事情。糟糕，糟糕的代码，不是吗？也许更好的解决方案就像dispatch_group_wait（）？

   // wait for wsDataVideos has finished. IT SEEMS THIS COLLAPSES CPU ¿?
   while (wsDataVideos.imported==NO) {
        sleep(1)
  }

while（condition）{}是否会破坏NSRURLConnection的连接？

1 个答案: