ios - 如何在 iOS 后台模式下下载文件？和网络连接丢失

Question

在我的应用程序中，我从服务器下载音频文件，当应用程序处于前台时，当我单击主页按钮或锁定按钮强制应用程序进入后台时，文件下载正常，然后过了一段时间，下载停止，错误出现为 1005 network connection lost。有什么问题？谁能解释一下这个问题？

代码:

     NSURL *url = [NSURL URLWithString:currentURL];
            NSURLRequest *theRequest = [NSURLRequest requestWithURL:url         cachePolicy:NSURLRequestReloadIgnoringLocalCacheData  timeoutInterval:60];
            receivedData = [[NSMutableData alloc] initWithLength:0];
            NSURLConnection * connection = [[NSURLConnection alloc] initWithRequest:theRequest delegate:self     startImmediately:YES];
            myConnection = connection;            
            NSLog(@"%@ Download Started", currentURL);


- (void) connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
    [UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
    [receivedData setLength:0];
    expectedBytes = [response expectedContentLength];
}

- (void) connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
    [receivedData appendData:data];
    float progressive = (float)[receivedData length] / (float)expectedBytes;
    [downloadProgressView setProgress:progressive];
    NSInteger val = progressive*100;
    downloadpercentageLabel.text = [NSString stringWithFormat:@"%ld%@",(long)val,@"%"];       
    //[UIApplication sharedApplication].idleTimerDisabled = YES;       
}

- (void) connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
    [UIApplication sharedApplication].networkActivityIndicatorVisible = NO;   
}

Answer 1

使用后台 NSURLSession。它可以处理网络中断和超过 3 分钟的下载。参见 Downloading Content in the Background iOS 应用程序编程指南 的部分，其中描述了后台下载。另请参阅 What’s New in Foundation Networking 中的 WWDC 2013 视频(稍后将在视频中介绍)。