以下代码创建一个AVPlayerViewController，但是11.4模拟器上缺少该视图。在模拟器上，最后一个命令获取UIKit`UIViewAlertForUnsatisfiableConstraints：
在我的iPad（9.3）上，它可以正常运行并显示视频。
AVPlayerItem * playerItem= [AVPlayerItem playerItemWithURL:[NSURL
URLWithString:model.currentCamera.videoUrl]];
model.playerViewController = AVPlayerViewController.new;
model.playerViewController.player = [AVPlayer playerWithPlayerItem:playerItem];
UIView *xy = model.playerViewController.view;
这是UIViewAlertForUnsatisfiableConstraints的显示内容
UIWindow:0x7fb19ce1a780
| UIView:0x7fb19cf0c270
| | NavBar:0x7fb19ce03c60
| | | UIButton:0x7fb19cf05830
| | | | UIImageView:0x7fb19cf06670
| | | UIButton:0x7fb19cd135d0
| | | | UIImageView:0x7fb19cd13d10
| | | UILabel:0x7fb19cd13f40'Current route name'
| | | UIView:0x7fb19cd16740
| | | UIButton:0x7fb19cd16930'Main View'
| | | | UIButtonLabel:0x7fb19cd16df0'Main View'
| | | UIButton:0x7fb19cd14220'List View'
| | | | UIButtonLabel:0x7fb19cd14540'List View'
| | | UIButton:0x7fb19cd17ab0'Map View'
| | | | UIButtonLabel:0x7fb19cd17dd0'Map View'
| | | UIButton:0x7fb19cd180d0'Traffic Radio'
| | | | UIButtonLabel:0x7fb19cd183f0'Traffic Radio'
| | | UIButton:0x7fb19cd186f0'Report'
| | | | UIButtonLabel:0x7fb19cd18a10'Report'
| | | UIView:0x7fb19cd18d10
| | TabBar1:0x7fb19cd18f00
| | | UIView:0x7fb19cd19350
| | | UIImageView:0x7fb19cd19540
| | | UILabel:0x7fb19cd1b7a0'Home'
| | | UIImageView:0x7fb19cd1be30
| | | UILabel:0x7fb19cd1d5e0'Cameras'
| | | UIImageView:0x7fb19cd1da70
| | | UILabel:0x7fb19cd1f220'Route'
| | | UIImageView:0x7fb19cd1f6b0
| | | UILabel:0x7fb19cd20e60'More'
| | UILabel:0x7fb19cf10c20'
To be filled in. This s...'
| | ViewOneCamera:0x7fb19cf27900
| | | UIImageView:0x7fb19cf32830
| | | UIButton:0x7fb19cf32fe0
| | | | UIImageView:0x7fb19cf33300
| | | UIButton:0x7fb19cf33530'Pause'
| | | | UIButtonLabel:0x7fb19cf33850'Pause'