swift - AVPlayer addObserver 永远不会被调用

Question

我正在尝试获取 AVPlayer timedMetadata，但永远不会调用观察者

self.metaItem!.addObserver(self, forKeyPath: "metaData", options: NSKeyValueObservingOptions(), context: nil)
        metPlayer=AVPlayer(playerItem: metaItem)
        metPlayer.play()
...

override func observeValue(forKeyPath keyPath: String?, of object: Any?, change:
        [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
        if keyPath != "metaData" { return }
        print("...")
    }

但是 MPMoviePlayerController 工作正常

谢谢。

Answer 1

metaItem AVPlayerItem 应该观察关键路径 timedMetadata ，但不是“元数据”:

self.metaItem!.addObserver(self, forKeyPath: "timedMetadata", options: NSKeyValueObservingOptions(), context: nil)