用于HLS缓存的AVAssetDownloadDelegate方法没有被调用

Question

我遵循了这里给出的HLS缓存教程，但是控件从未到达任何委托(AVAssetDownloadDelegate)。

我错过什么了吗?下面是我写的代码

- (void)setupAssetDownloader {
    NSURL *assetURL = [NSURL URLWithString:@"STREAMING_HOST/video/hls/3729170.m3u8"];
    AVURLAsset *hlsAsset = [AVURLAsset assetWithURL:assetURL];
    urlSessionConfiguration = [NSURLSessionConfiguration backgroundSessionConfigurationWithIdentifier:@"assetDowloadConfigIdentifier"];
    avAssetDownloadSession = [AVAssetDownloadURLSession sessionWithConfiguration:urlSessionConfiguration assetDownloadDelegate:self delegateQueue:[NSOperationQueue mainQueue]];
    // Download movie
    avAssetDownloadTask = [avAssetDownloadSession assetDownloadTaskWithURLAsset:hlsAsset assetTitle:@"downloadedMedia" assetArtworkData:nil options:nil];
//@{AVAssetDownloadTaskMinimumRequiredMediaBitrateKey : @(300000)}

    [avAssetDownloadTask resume];
    AVPlayerItem *playerItem = [[AVPlayerItem alloc] initWithAsset:avAssetDownloadTask.URLAsset];
    AVPlayer *player = [[AVPlayer alloc ] initWithPlayerItem:playerItem];
    AVPlayerLayer *playerLayer = [[AVPlayerLayer alloc ] init];
    [playerLayer setPlayer:player];
    [playerLayer setFrame:self.view.frame];
    [self.view.layer addSublayer:playerLayer];
    [player play];
}
#pragma mark - AVAssetDownloadDelegate
- (void)URLSession:(NSURLSession *)session assetDownloadTask:(AVAssetDownloadTask *)assetDownloadTask didResolveMediaSelection:(AVMediaSelection *)resolvedMediaSelection {
}
- (void)URLSession:(NSURLSession *)session assetDownloadTask:(AVAssetDownloadTask *)assetDownloadTask didLoadTimeRange:(CMTimeRange)timeRange totalTimeRangesLoaded:(NSArray<NSValue *> *)loadedTimeRanges timeRangeExpectedToLoad:(CMTimeRange)timeRangeExpectedToLoad {
    NSInteger percent = 0;
    for (NSValue *value in loadedTimeRanges) {
        CMTimeRange timeRange = [value CMTimeRangeValue];
        percent += CMTimeGetSeconds(timeRange.duration) / CMTimeGetSeconds(timeRangeExpectedToLoad.duration);
    }
    percent *= 100;
    NSLog(@"Progress: %ld", (long)percent);
}
- (void)URLSession:(NSURLSession *)session assetDownloadTask:(AVAssetDownloadTask *)assetDownloadTask didFinishDownloadingToURL:(NSURL *)location {
    NSString *localPath = location.relativePath;
    NSLog(@"localPath: %@", localPath);
    // TODO: Play downloaded file
    // IMPORTANT: Don't move this file to another location.
}

Answer 1

我在模拟器上运行代码，

模拟器不支持下载HLS流。

当我使用下面提到的委托方法时，我发现了这个问题。

- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error {
}

经过一整天的努力，我在这里找到了一个苹果公司的样本，找到了问题背后的真正原因。

Answer 2

我最近遇到了同样的症状。

原来我的应用程序中有另一个对象设置后台URL会话。

let configuration = URLSessionConfiguration.background(withIdentifier: "[id]") 

一旦我删除了其他会话，我就开始得到预期的回调。

也许在某个地方记录了应用程序不应该设置多个后台下载会话，但无论如何，这解决了我的问题