ios - 如何通过自定义渐变更改 strokeColor

Question

我想为 CAShapeLayer 的 strokeColor 设置动画，但在 CABasicAnimation 中我有两个值(from 和 to)。动画火时是否只支持两种颜色？例如，开始时我有 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];

在中途我有一个深紫色，但我需要，例如，黄色。

是否可以向 CABasicAnimation 添加自定义渐变？

Answer 1

我不认为你可以用 CABasicAnimation 做到这一点，但你可以使用 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];

如果你想要一种“跨越光谱”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，如果您想要更多简单的蓝色到红色，但又要避免深紫色，您可以这样做:

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]];

很多选项。