当应用程序在后台时无法从服务器获取响应 - iOS4

我知道Apple支持在后台模式下运行的应用程序，我想要做的是发送http请求以从服务器获取数据，然后为用户提供一些通知，并且我想要在几次使用timmer期间重复此操作。我正在使用XCode-3.2.4和Iphone4.1模拟器，它支持后台运行，但是当我向我的服务器发出http请求时，没有调用响应函数。任何人都可以帮助我如何做到这一点？请。这样的代码：当应用程序在后台时无法从服务器获取响应 - iOS4

- (void)applicationDidEnterBackground:(UIApplication *)application{ 
UIApplication* app = [UIApplication sharedApplication]; 

bgTask = [app beginBackgroundTaskWithExpirationHandler:^{ 
    [app endBackgroundTask:bgTask]; 
    bgTask = UIBackgroundTaskInvalid; 
}]; 
// Start the long-running task and return immediately. 
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ 
    // Do the work associated with the task. 

    responseData = [[NSMutableData data] retain]; 
    NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:@"http://www.unpossible.com/misc/lucky_numbers.json"]]; 
    [[NSURLConnection alloc] initWithRequest:request delegate:self]; 

    }); 
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response { 
[responseData setLength:0]; 
NSLog(@"%@",@"Server responded"); 
} 

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data { 
[responseData appendData:data]; 
NSLog(@"%@",@"Server transfered data"); 
} 

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error { 
NSLog(@"%@",[NSString stringWithFormat:@"Connection failed: %@", [error description]]); 
} 

- (void)connectionDidFinishLoading:(NSURLConnection *)connection { 
[connection release]; 
NSLog(@"%@",@"Server transfered data"); 
UIApplication* app = [UIApplication sharedApplication]; 
[app endBackgroundTask:bgTask]; 
bgTask = UIBackgroundTaskInvalid; 
}

来源

2010-10-08 Crisk

改为做同步请求。似乎你只能在后台使用一个线程。

NSURLResponse *response; 
[NSURLConnection sendSynchronousRequest:request returningResponse:&response error:nil];

来源

2010-12-21 15:47:21

当应用程序在后台时无法从服务器获取响应 - iOS4

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