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 |
|
frame |
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 |
|
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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 |
|
|
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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 |
|
|
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8.遮罩 (Mask Properties)
| Field Key Path |
Remark |
En Description |
| mask |
|
|
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9.ShapeLayer属性 (ShapeLayer)
| Field Key Path |
Remark |
En Description |
| fillColor |
|
|
| strokeColor |
|
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| 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 |
|
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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
三、参考资料
