使用 AV 时未开始动画

Question

我设置了一个项目作为测试，使用AVSyncronizedLayer在屏幕上移动红线(CALayer)作为电影播放。

当我这样做的时候，我参考了这里给出的答案，并包含了解决方案，但是当视频开始时，动画没有开始。

如果有人知道我哪里错了，那将非常有帮助。代码是:

- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
//create the red line sublayer
redLine = [CALayer layer];
redLine.backgroundColor = [UIColor redColor].CGColor;
redLine.frame = CGRectMake(engravingControl.frame.origin.x, engravingControl.center.y - (engravingControl.frame.size.height/2), 3, engravingControl.frame.size.height);

//create the AVplayer object
NSURL *fileURL = [[NSBundle mainBundle] URLForResource:@"IMG_1306" withExtension:@"mov"];
AVURLAsset *asset = [AVURLAsset URLAssetWithURL:fileURL options:nil];
AVPlayerItem *playerItem = [AVPlayerItem playerItemWithAsset:asset];
AVPlayer *player = [AVPlayer playerWithPlayerItem:playerItem];
AVPlayerLayer *playerLayer = [AVPlayerLayer playerLayerWithPlayer:player];
playerLayer.frame = CGRectMake(0, 0,400,300);
playerLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
//add the subViews
[self.view.layer addSublayer:playerLayer];
[self.view.layer addSublayer:redLine];
CABasicAnimation *redLineMove;  
redLineMove=[CABasicAnimation animationWithKeyPath:@"transform.translation.x"];
redLineMove.duration=10;
redLineMove.fromValue=[NSNumber numberWithFloat:engravingControl.frame.origin.x];
redLineMove.toValue=[NSNumber numberWithFloat:engravingControl.frame.size.width + engravingControl.frame.origin.x];
redLineMove.beginTime = AVCoreAnimationBeginTimeAtZero;

//create the sync layer
AVSynchronizedLayer *syncLayer = [AVSynchronizedLayer     synchronizedLayerWithPlayerItem:playerItem];
[syncLayer addSublayer:redLine];
[redLine addAnimation:redLineMove forKey:@"redLineMove"];
[self.view.layer addSublayer:syncLayer];
[player play];
}

Answer 1

我发现了一个解决方案。如果没有以下代码行:

animation.removedOnCompletion = NO;

然后动画永远不会开始(我假设它在电影开始播放之前被CA删除)。