@property (nonatomic, retain, nullable) AVPlayer *player;
NSString *urlStr= [[NSBundle mainBundle]pathForResource:@"demo.mp4" ofType:nil];
NSURL *url=[NSURL fileURLWithPath:urlStr];
AVPlayerItem *playerItem=[AVPlayerItem playerItemWithURL:url];
_player=[AVPlayer playerWithPlayerItem:playerItem];
//没这句话会死很久的，，，，
AVPlayerLayer *playerLayer=[AVPlayerLayer playerLayerWithPlayer:];
= ;
[ addSublayer:playerLayer];
[ play];