如何通过自定义渐变更改strokeColor

Question

我想动画CAShapeLayer的strokeColor，但在CABasicAnimation中，我有两个值（from和to）。只有两种颜色支持，而动画是火吗？例如，在开始我strokeColor = [UIColor blueColor].CGColor; 然后

CABasicAnimation *colorAnimation = [CABasicAnimation animationWithKeyPath:@"strokeColor"]; 
colorAnimation.duration   = 3.0; // "animate over 3 seconds or so.." 
colorAnimation.repeatCount   = 1.0; // Animate only once.. 
colorAnimation.removedOnCompletion = NO; // Remain stroked after the animation.. 
colorAnimation.fillMode = kCAFillModeForwards; 
colorAnimation.toValue = (id)[UIColor redColor].CGColor; 
colorAnimation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseIn]; 

在中途我有一个暗紫色的颜色，但我需要的，例如，黄色。

是否可以向CABasicAnimation添加自定义渐变？

Answer 1

我不认为你可以做到这一点CABasicAnimation，但你可以使用一个CAKeyframeAnimation为动画设置中间值：

CAKeyframeAnimation *colorAnimation = [CAKeyframeAnimation animationWithKeyPath:@"strokeColor"]; 
colorAnimation.values    = @[(id)[[UIColor blueColor] CGColor], 
             (id)[[UIColor yellowColor] CGColor], 
             (id)[[UIColor redColor] CGColor]]; 
colorAnimation.duration    = 3.0; // "animate over 3 seconds or so.." 
colorAnimation.repeatCount   = 1.0; // Animate only once.. 
colorAnimation.removedOnCompletion = NO; // Remain stroked after the animation.. 
colorAnimation.fillMode    = kCAFillModeForwards; 
colorAnimation.timingFunction  = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseIn]; 

如果你想要一个“跨越谱”之类的感觉，你可以这样做：

colorAnimation.values = @[(id)[[UIColor blueColor] CGColor], 
          (id)[[UIColor greenColor] CGColor], 
          (id)[[UIColor yellowColor] CGColor], 
          (id)[[UIColor orangeColor] CGColor], 
          (id)[[UIColor redColor] CGColor]]; 

或者，如果你想要更多的一个简单的蓝色的红色，但避免了真正的暗紫色，你可以这样做：

colorAnimation.values = @[(id)[[UIColor blueColor] CGColor], 
          (id)[[UIColor colorWithRed:0.9 green:0.0 blue:0.9 alpha:1.0] CGColor], 
          (id)[[UIColor redColor] CGColor]]; 

很多选择。