如何消除两个连续 CAKeyframeAnimation 动画之间的奇怪延迟？

Question

iOS 编码器！

此代码用于动画小红方块以在UIView 上绘制大符号“8”。首先是上环（animSequence1 = 5 秒），然后是下环（animSequence2 = 再过 5 秒）。
无需延迟！
但是我在两个连续动画之间遇到了奇怪的延迟（大约 1 秒）。这个延迟是从哪里来的？！？

代码：

- (void)drawRect:(CGRect)drawRect {
   CGContextRef context = UIGraphicsGetCurrentContext();
   drawRect = CGRectMake(0, 0, 320, 320);
   CGContextSetFillColorWithColor(context, [UIColor blueColor].CGColor;);
   CGContextFillRect(context, drawRect);

   // Little red square
   CALayer *layerTest;
   layerTest = [CALayer layer];
   layerTest.bounds = CGRectMake(0, 0, 20, 20);
   layerTest.anchorPoint = CGPointMake(0, 0);
   layerTest.backgroundColor = [UIColor redColor].CGColor;
   [[self layer] addSublayer:layerTest];

   // Upper ring
   CAKeyframeAnimation *animSequence1;
   animSequence1 = [CAKeyframeAnimation animationWithKeyPath:@"position"];
   animSequence1.fillMode = kCAFillModeForwards;
   animSequence1.removedOnCompletion = NO;
   animSequence1.autoreverses = NO;
   animSequence1.repeatCount = 0;
   animSequence1.duration = 5.0;
   animSequence1.beginTime = 0.0;
   animSequence1.path = [UIBezierPath bezierPathWithArcCenter:CGPointMake(200, 120) radius:80 startAngle:DEG_TO_RAD(90) endAngle:DEG_TO_RAD(450) clockwise:YES].CGPath;
   animSequence1.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];

   // Lower ring
   CAKeyframeAnimation *animSequence2;
   animSequence2 = [CAKeyframeAnimation animationWithKeyPath:@"position"];
   animSequence2.fillMode = kCAFillModeForwards;
   animSequence2.removedOnCompletion = NO;
   animSequence2.autoreverses = NO;
   animSequence2.repeatCount = 0;
   animSequence2.duration = 5.0;
   animSequence2.beginTime = 5.0;
   animSequence2.path = [UIBezierPath bezierPathWithArcCenter:CGPointMake(200, 280) radius:80 startAngle:DEG_TO_RAD(-90) endAngle:DEG_TO_RAD(-450) clockwise:NO].CGPath;
   animSequence2.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];

   // A sequence of animations
   CAAnimationGroup *animGroup;
   layerTest.position = CGPointMake(200, 200);
   animGroup = [CAAnimationGroup animation];
   animGroup.duration = 10.0;
   animGroup.animations = [NSArray arrayWithObjects:animSequence1, animSequence2, nil];

   [layerTest addAnimation:animGroup forKey:nil];
}

我也试过不用CAAnimationGroup。
为第一个CAKeyframeAnimation (animSequence1) 设置[animSequence1 setDelegate:self];，然后由(void)animationDidStop 启动第二个CAKeyframeAnimation (animSequence2)。
它的工作原理相同，但是两个动画之间的这种奇怪的延迟（大约 1 秒）没有消失！

问题：如何消除两个连续的CAKeyframeAnimation 动画之间的奇怪延迟？ 无需延迟！

Answer 1

不要在-drawRect: 中创建图层或动画——您无法完全控制何时调用它，因此您最终会在视图中添加多个layerTests，所有人都试图单独制作动画。在初始化程序中创建图层/动画，或响应某些用户交互。

我还建议在animSequence1 上删除您的fillMode 和removedOnCompletion 设置；一旦animSequence2 启动，您实际上是在要求 CA 在同一属性上运行两个非累加动画一次。不确定这种行为是否定义明确，但这是怪异可能来自的另一个地方。