AVPlayer实现边下边播

声明两个对象，avplayer是播放器，avplayeritem是播放条目信息

var player:AVPlayer?
var playerItem:AVPlayerItem?

  let url = URL(string: "xxxx")! //设置播放的URL
  playerItem=AVPlayerItem(url: url!)
  player=AVPlayer(playerItem: playerItem)
player?.addPeriodicTimeObserver(forInterval: CMTimeMake(1, 1), queue: DispatchQueue.main, using: { (time) in
//这里可以处理播放进度，queue最好换成其他线程进行计算，然后在mainqueue中更新ui
}
self.playerItem?.addObserver(self, forKeyPath: "status", options: [.initial,.new], context: nil)//观察状态
self.playerItem?.addObserver(self, forKeyPath: "loadedTimeRanges", options: [.initial,.new], context: nil)//观察缓冲进度
self.playerItem?.addObserver(self, forKeyPath: "playbackLikelyToKeepUp", options: [.initial,.new], context: nil)//缓存可以播放的时候调用

处理观察者

override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
        if "status"==keyPath{
            switch player!.currentItem!.status {
            case .readyToPlay:
              //当前可播放，可以选择立即播放
            player?.play()
            case .unknown:
             //尚未获取媒体信息
            case .failed:
             //不可播放
            //player?.currentItem?.error可查看错误
}
}else if "loadedTimeRanges"==keyPath{
         //当前缓冲进度
        }else if "playbackLikelyToKeepUp"==keyPath{
        //是否可播放
        }

可用seek方法跳转指定位置播放。