在Core Animation中， 借助Core Animation 提供的几个动画类我们可以对一个Layer做各种酷炫的动画，在实例 CAPropertyAnimation 的时候（ CABasicAnimation 和 CAKeyFrameAnimation均继承自该类），通过构造方法 convenience init(keyPath path: String?)，需要传入一个字符串。 那么问题来了，这个参数到底可以取哪些值呢？
我们知道 CALayer 实现了 NSKeyValueCoding 协议，因此我们可以使用 KVC 对 CALayer的实例中的属性进行取值和赋值，而在 Core Animation 提供的几个动画类影响的对象便是 CALayer的实例，我们可以推测在 CAPropertyAnimation 类中构造方法 convenience init(keyPath path: String?) 的keyPath参数的取值 应该是 CALayer 中的属性。 带着这个推测，参考苹果的官方文档，笔者把可以用作keyPath的值列举如下。
一、可动画属性
1. 几何属性 (Geometry Properties)
| Field Key Path | Remark | En Description | |
|---|---|---|---|
| transform.rotation.x | 按x轴旋转的弧度 | Set to an NSNumber object whose value is the rotation, in radians, in the x axis. | |
| transform.rotation.y | 按y轴旋转的弧度 | Set to an NSNumber object whose value is the rotation, in radians, in the y axis. | |
| transform.rotation.z | 按z轴旋转的弧度 | Set to an NSNumber object whose value is the rotation, in radians, in the z axis. | |
| transform.rotation | 按z轴旋转的弧度, 和transform.rotation.z效果一样 | Set to an NSNumber object whose value is the rotation, in radians, in the z axis. This field is identical to setting the rotation.z field. | |
| transform.scale.x | 在x轴按比例放大缩小 | Set to an NSNumber object whose value is the scale factor for the x axis. | |
| transform.scale.y | 在x轴按比例放大缩小 | Set to an NSNumber object whose value is the scale factor for the y axis. | |
| transform.scale.z | 在z轴按比例放大缩小 | Set to an NSNumber object whose value is the scale factor for the z axis. | |
| transform.scale | 按比例放大缩小 | Set to an NSNumber object whose value is the average of all three scale factors. | |
| transform.translation.x | 沿x轴平移 | Set to an NSNumber object whose value is the translation factor along the x axis. | |
| transform.translation.y | 沿y轴平移 | Set to an NSNumber object whose value is the translation factor along the y axis. | |
| transform.translation.z | 沿z轴平移 | Set to an NSNumber object whose value is the translation factor along the z axis. | |
| transform.translation | x,y 坐标均发生改变 | Set to an NSValue object containing an NSSize or CGSize data type. That data type indicates the amount to translate in the x and y axis. | |
| transform | CATransform3D 4*4矩阵 | ||
| bounds | layer大小 | ||
| position | layer位置 | ||
| 不支持 frme 属性 | computed from the bounds and position and is NOT animatable | ||
| anchorPoint | 锚点位置 | ||
| cornerRadius | 圆角大小 | ||
| zPosition | z轴位置 |
2.背景属性 (Background Properties)
| Field Key Path | Remark | En Description | |
|---|---|---|---|
| backgroundColor | 背景颜色 |
3.Layer内容 (Layer Content)
| Field Key Path | Remark | En Description |
|---|---|---|
| contents | Layer内容，呈现在背景颜色之上 | |
| contentsRect | The rectangle, in the unit coordinate space, that defines the portion of the layer’s contents that should be used. | |
| masksToBounds | setting the layer’s masksToBounds property to YES does cause the layer to clip to its corner radius |
4.子Layer内容 (Sublayers Content)
| Field Key Path | Remark | En Description |
|---|---|---|
| sublayers | 子Layer数组 | |
| sublayerTransform | 子Layer的Transform | Specifies the transform to apply to sublayers when rendering. |
5.边界属性 (Border Attributes)
| Field Key Path | Remark | En Description | |
|---|---|---|---|
| borderColor | |||
| borderWidth |
6.阴影属性 (Shadow Properties)
| Field Key Path | Remark | En Description | |
|---|---|---|---|
| shadowColor | 阴影颜色 | ||
| shadowOffset | 阴影偏移距离 | ||
| shadowOpacity | 阴影透明度 | ||
| shadowRadius | 阴影圆角 | ||
| shadowPath | 阴影路径 |
7.透明度 (Opacity Property)
| Field Key Path | Remark | En Description | |
|---|---|---|---|
| opacity | 透明度 | ||
| hiden |
8.遮罩 (Mask Properties)
| Field Key Path | Remark | En Description | |
|---|---|---|---|
| mask |
9.ShapeLayer属性 (ShapeLayer)
| Field Key Path | Remark | En Description | |
|---|---|---|---|
| fillColor | |||
| strokeColor | |||
| strokeStart | 从无到有 | ||
| strokeEnd | 从有到无 | ||
| lineWidth | 路径的线宽 | ||
| miterLimit | 相交长度的最大值 | ||
| lineDashPhase | 虚线样式 |
二、注意
这里特别需要注意的是 layer的 frame 是不支持动画的，我们可以通过改变position和````bounds``` 变通实现
