Ios swift中的AVPlayerViewController和AVPlayer'；我什么也没表现出来

我正在尝试使用AVPlayer在avplayervewcontroller中播放来自文档路径的mp4视频，但它没有在屏幕上显示任何内容。我做错了什么

这里是模拟器的屏幕截图：

这是我的代码：

func startPlayer(filePath:String)
{
    let dirPaths = NSSearchPathForDirectoriesInDomains(.DocumentDirectory,.UserDomainMask, true)
    let docsDir = dirPaths[0]


    let filePath = (docsDir as NSString).stringByAppendingPathComponent(videos[videoNo]._Name)

    playerVC=AVPlayerViewController()
    playerVC!.view.frame=self.view.bounds
    playerVC!.view.layer.zPosition = 1;


    var videoURL = NSURL(string: filePath)
    var player = AVPlayer(URL: videoURL!)
    var playerLayer = AVPlayerLayer(player: player)
    playerLayer.frame = playerVC!.view.bounds
    playerVC!.view.layer.addSublayer(playerLayer)

    playerVC!.player=player
    self.view.addSubview(playerVC!.view)

    playerVC!.player!.play()
}

---

使用

AVAsset

作为播放器的源代码

let currentVideoAsset = AVAsset(URL: outputFileURL)


self.player = AVPlayer(playerItem: AVPlayerItem(asset:currentVideoAsset))

---

我找到了，我换了这个

var videoURL = NSURL(string: filePath)

用这个

var videoURL = NSURL(fileURLWithPath: filePath)

而且正在工作