objective-c - AVPlayer无法播放本地视频文件
如题，AVPlayer这货整死不播放本地视频文件(视频绝对没问题)，而网络加载链接是可以播放的，烦劳各位大大看看咋回事？
代码如下：
NSURL *url = [NSURL fileURLWithPath:@"/Users/tangkunyin/Desktop/mp4ForDownloadTest.mp4"];
AVAsset *movieAsset = [AVURLAsset assetWithURL:url];
AVPlayerItem *playerItem = [AVPlayerItem playerItemWithAsset:movieAsset];
AVPlayer *player = [AVPlayer playerWithPlayerItem:playerItem];
AVPlayerLayer *playerLayer = [AVPlayerLayer playerLayerWithPlayer:player];
playerLayer.frame = CGRectMake(0, 0, KDeviceWidth, 300);
playerLayer.videoGravity=AVLayerVideoGravityResize;
[self.view.layer addSublayer:playerLayer];
[player play];