CAKeyFrameAnimation 中的 keyTime 是什么样的值？
例如，我有这个 CAKeyFrameAnimation：
CALayer* theLayer = myView.layer;
CAKeyframeAnimation* animation;
animation = [CAKeyframeAnimation animationWithKeyPath:@"transform.rotation.z"];
animation.duration = 1.6;
//animation.cumulative = YES;
animation.repeatCount = 1;
animation.removedOnCompletion = NO;
animation.fillMode = kCAFillModeForwards;
animation.values = [NSArray arrayWithObjects:
[NSNumber numberWithFloat:0.0 * M_PI],
[NSNumber numberWithFloat:(15.0/180.0) * M_PI],
[NSNumber numberWithFloat:(30.0/180.0) * M_PI], // animation stops here...
[NSNumber numberWithFloat:(45.0/180.0) * M_PI], // ignored!
[NSNumber numberWithFloat:(190.0/180.0) * M_PI], nil]; // ignored!
animation.keyTimes = [NSArray arrayWithObjects:
[NSNumber numberWithFloat:0.0],
[NSNumber numberWithFloat:0.2],
[NSNumber numberWithFloat:0.4], // ignored!
[NSNumber numberWithFloat:0.8], // ignored!
[NSNumber numberWithFloat:1.6], nil]; // ignored!
animation.timingFunctions = [NSArray arrayWithObjects:
[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear],
[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear],
[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear],
[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear],
[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear], nil];
[theLayer addAnimation:animation forKey:@"transform.rotation.z"];
我不明白的是：
A）关键时间值是自动画开始以来的绝对经过时间吗？
B) 关键时间值只是说明该特定关键帧要使用多少时间？
For example I have this CAKeyFrameAnimation:
CALayer* theLayer = myView.layer;
CAKeyframeAnimation* animation;
animation = [CAKeyframeAnimation animationWithKeyPath:@"transform.rotation.z"];
animation.duration = 1.6;
//animation.cumulative = YES;
animation.repeatCount = 1;
animation.removedOnCompletion = NO;
animation.fillMode = kCAFillModeForwards;
animation.values = [NSArray arrayWithObjects:
[NSNumber numberWithFloat:0.0 * M_PI],
[NSNumber numberWithFloat:(15.0/180.0) * M_PI],
[NSNumber numberWithFloat:(30.0/180.0) * M_PI], // animation stops here...
[NSNumber numberWithFloat:(45.0/180.0) * M_PI], // ignored!
[NSNumber numberWithFloat:(190.0/180.0) * M_PI], nil]; // ignored!
animation.keyTimes = [NSArray arrayWithObjects:
[NSNumber numberWithFloat:0.0],
[NSNumber numberWithFloat:0.2],
[NSNumber numberWithFloat:0.4], // ignored!
[NSNumber numberWithFloat:0.8], // ignored!
[NSNumber numberWithFloat:1.6], nil]; // ignored!
animation.timingFunctions = [NSArray arrayWithObjects:
[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear],
[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear],
[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear],
[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear],
[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear], nil];
[theLayer addAnimation:animation forKey:@"transform.rotation.z"];
What I don't get is:
A) are key time values absolute passed time since the animation has started?
B) are key time values just saying how much time to use for this particular key frame?
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docs 这里的措辞有点奇怪，但很准确：
基本上，每个值都指示给定关键帧发生在动画中的哪个标准化点。因此，如果关键帧占动画的 25%，则该值将为 0.25。文档中令人困惑的部分是它们表明这是一个持续时间，而实际上它是一个标准化的时间点。
The docs are phrased a little oddly here, but are accurate:
Basically, each value indicates at what normalized point in the animation the given keyframe occurs. So if a keyframe is 25% into the animation, the value would be 0.25. The confusing part of the docs is they indicate that it is a duration, when in fact it's a normalized point in time.
keyTimes 的值是总持续时间的百分比。有效值范围为 0 到 1（0% 到 100%）。您最后的值 1.6 无效。
举个例子，如果一个关键帧应该发生在动画的 0.8 秒处，那么在持续时间为 1.6 秒的情况下，keyTime 将为 0.5。
The value of keyTimes is a percent of the total duration. Valid values range between 0 and 1 (0% to 100%). Your last value of 1.6 is invalid.
As an example, if a keyframe is supposed to happen 0.8 seconds into the animation that keyTime would be 0.5 given your duration of 1.6 seconds.