Objective c AVVideoCompositionCoreAnimationTool未添加所有Calayer

好吧，这件事把我难住了。如果您需要，我很乐意发布其他代码，但我认为这已经足够了。我一辈子都搞不明白为什么事情会出差错。我正在使用AVVideoCompositionCoreAnimationTool将包含图像的CALayers添加到合成中。我创建了一个包含所有要添加的注释的NSArray（请参见下面的界面），然后使用枚举器将它们添加到动画层。据我所知，不管数组中有多少注释，最后输出的视频中只有最后一个循环添加的注释。有人能发现我遗漏了什么吗

这是注释的界面

@interface Annotation : NSObject// <NSCoding>

@property float time;
@property AnnotationType type;
@property CALayer *startLayer;
@property CALayer *typeLayer;
@property CALayer *detailLayer;

+ (Annotation *)annotationAtTime:(float)time ofType:(AnnotationType)type;

- (NSString *)annotationString;

@end

---

我想强调的是，视频输出是正确的，我确实在正确的时间得到了层的显示，只是不是所有的层。非常困惑，非常感谢您的帮助。

因此，我一直在尝试找出导致此问题的原因，结果发现这是由layers hidden属性设置为YES引起的。通过将其设置为“否”，所有层都会出现，但它们从未消失。因此，我必须将动画的autoreverses属性更改为YES，并将持续时间减半

因此，我将代码更改为：

while (ann = (Annotation *)[enumerator nextObject]){
  CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"opacity"];
  animation.duration = 1.5; // TODO: Three seconds is the currently hard-coded display length for an annotation, should this be a configurable option after the demo?
  animation.repeatCount = 0;
  animation.autoreverses = YES; // This causes the animation to run forwards then backwards, thus doubling the duration, that's why a 3-second period is using 1.5 as duration
  animation.removedOnCompletion = NO;
  animation.fromValue = [NSNumber numberWithFloat:1.0];
  animation.toValue = [NSNumber numberWithFloat:1.0];
  animation.beginTime = time;
  //  animation.beginTime = AVCoreAnimationBeginTimeAtZero;

  ann.startLayer.hidden = NO;
  ann.startLayer.opacity = 0.0;
  ann.startLayer.masksToBounds = YES;
  [ann.startLayer addAnimation:animation forKey:@"animateOpacity"];
  [animationLayer addSublayer:ann.startLayer];

  ann.typeLayer.hidden = NO;
  ann.typeLayer.opacity = 0.0;
  ann.typeLayer.masksToBounds = YES;
  [ann.typeLayer addAnimation:animation forKey:@"animateOpacity"];
  [animationLayer addSublayer:ann.typeLayer];

  ann.detailLayer.hidden = NO;
  ann.detailLayer.opacity = 0.0;
  ann.detailLayer.masksToBounds = YES;
  [ann.detailLayer addAnimation:animation forKey:@"animateOpacity"];
  [animationLayer addSublayer:ann.detailLayer];
}

while (ann = (Annotation *)[enumerator nextObject]){
  CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"opacity"];
  animation.duration = 1.5; // TODO: Three seconds is the currently hard-coded display length for an annotation, should this be a configurable option after the demo?
  animation.repeatCount = 0;
  animation.autoreverses = YES; // This causes the animation to run forwards then backwards, thus doubling the duration, that's why a 3-second period is using 1.5 as duration
  animation.removedOnCompletion = NO;
  animation.fromValue = [NSNumber numberWithFloat:1.0];
  animation.toValue = [NSNumber numberWithFloat:1.0];
  animation.beginTime = time;
  //  animation.beginTime = AVCoreAnimationBeginTimeAtZero;

  ann.startLayer.hidden = NO;
  ann.startLayer.opacity = 0.0;
  ann.startLayer.masksToBounds = YES;
  [ann.startLayer addAnimation:animation forKey:@"animateOpacity"];
  [animationLayer addSublayer:ann.startLayer];

  ann.typeLayer.hidden = NO;
  ann.typeLayer.opacity = 0.0;
  ann.typeLayer.masksToBounds = YES;
  [ann.typeLayer addAnimation:animation forKey:@"animateOpacity"];
  [animationLayer addSublayer:ann.typeLayer];

  ann.detailLayer.hidden = NO;
  ann.detailLayer.opacity = 0.0;
  ann.detailLayer.masksToBounds = YES;
  [ann.detailLayer addAnimation:animation forKey:@"animateOpacity"];
  [animationLayer addSublayer:ann.detailLayer];
}