AVAssetDownloadTask状态显示为已暂停

Question

我正在尝试暂停下载任务（如果正在下载）。但是AVAssetDownloadTask状态始终显示为暂停，即使正在进行正在进行的下载。

assetName = [assetName stringByReplacingOccurrencesOfString:@" " withString:@"++"];
    NSURLSessionConfiguration *urlSessionConfiguration = [NSURLSessionConfiguration backgroundSessionConfigurationWithIdentifier:[NSString stringWithFormat:@"%@",assetName]];
    urlSessionConfiguration.discretionary = YES;
    urlSessionConfiguration.sessionSendsLaunchEvents = YES;

    // Create a new AVAssetDownloadURLSession with background configuration, delegate, and queue
    AVAssetDownloadURLSession *avAssetDownloadSession = [AVAssetDownloadURLSession sessionWithConfiguration:urlSessionConfiguration assetDownloadDelegate:self delegateQueue:[NSOperationQueue mainQueue]];

    AVURLAsset *hlsAsset = [AVURLAsset assetWithURL:url];

    if (@available(iOS 10.0, *)) {

        //[AVAssetDownloadTaskMediaSelectionKey: mediaSelection]
        AVAssetDownloadTask *avAssetVidDownloadTask = [avAssetDownloadSession assetDownloadTaskWithURLAsset:hlsAsset assetTitle:[NSString stringWithFormat:@"%@",assetName] assetArtworkData:nil options:nil];
        if ([avAssetVidDownloadTask state] == NSURLSessionTaskStateSuspended) {
            [avAssetVidDownloadTask resume];
        }else{
            [avAssetVidDownloadTask suspend];
        }

    } else {
        // Fallback on earlier versions
    }