当状态为AVKeyValueStatusFailed时，重新加载AVAsset中的键 [英] Reloading keys in AVAsset when status is AVKeyValueStatusFailed

问题描述

我正在执行以下操作：

• 创建一个新的 AVAsset 给定的URL。该URL指向远程Web服务器上的视频。


• 通过调用尝试加载 track 属性loadValuesAsynchronouslyForKeys：completionHandler：


• 初始请求失败，因为没有互联网连接


• 我注意到请求失败了调用 statusOfValueForKey：错误：


• 然后我等待连接重新出现（使用一些可达性代码）。一旦这样做，我再次调用 loadValuesAsynchronouslyForKeys：completionHandler：。

• Create a new AVAsset with a given URL. That URL points to a video on a remote web server.
• Attempt to load the tracks property by calling loadValuesAsynchronouslyForKeys:completionHandler:
• The initial request fails, because no internet connection exists
• I notice that the request failed by calling statusOfValueForKey:error:
• I then wait for the connection to re-appear (using some reachability code). As soon as it does, I call loadValuesAsynchronouslyForKeys:completionHandler: again.

这是问题开始的地方。我会想象 AVAsset 继续尝试重新加载track属性，因为之前失败了。但是，这似乎不会发生。 statusOfValueForKey：错误：仍将返回 AVKeyValueStatusFailed ，尽管有可用的互联网连接并且视频可播放。

Here's where the problems begin. I would imagine that the AVAsset goes ahead and attempts to reload the tracks property since it failed previously. However, this does not seem to happen. statusOfValueForKey:error: will still return AVKeyValueStatusFailed, although a working internet connection is available and the video is playable.

有没有办法重置这个给定属性的状态并尝试另一个加载？还有另一种解决方法吗？

Is there a way to reset the state for this given property and to attempt another load? Is there another way to work around this?

推荐答案

1. 您是在创建新的AVURLAsset还是只是重用上一个？


2. 在的完成处理程序中，loadValuesAsynchronouslyForKeys：completionHandler：您是否已调度回主线程？

1. Are you creating a new AVURLAsset or just reusing the previous one?
2. In the completion handler for loadValuesAsynchronouslyForKeys:completionHandler: are you dispatching back to the main thread?

当你准备好重试时再次调用此方法（或类似的东西）会发生什么。

What happens if you call this method again (or something similar) when you're ready to retry.

- (void)setContentURL:(NSURL *)contentURL
{
    if (_contentURL != contentURL) {
        _contentURL = contentURL;

        AVURLAsset *asset = [AVURLAsset URLAssetWithURL:_contentURL options:nil];

        NSArray *requestedKeys = [NSArray arrayWithObjects:ISIVideoPlayerControllerTracksKey, ISIVideoPlayerControllerPlayableKey, nil];

        [asset loadValuesAsynchronouslyForKeys:requestedKeys completionHandler: ^{
             dispatch_async(dispatch_get_main_queue(), ^{
                 [self prepareToPlayAsset:asset withKeys:requestedKeys];
             });
         }];
    }
}

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