此篇文章主要讲述了CALayer与动画相关的一些操作属性。
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CALayer的说明
image.png
从中我们可以看出
CALayer遵循了三个代理协议，其中主要说说NSSecureCoding 和CAMediaTimingNSSecureCoding继承自NSCoding，NSSecureCoding和NSCoding是一样的，除了在解码时要同时指定key和要解码的对象的类，如果要求的类和从文件中解码出的对象的类不匹配，NSCoder会抛出异常，告诉你数据已经被篡改了。CAMediaTiming中包含了很多属性
/* The begin time of the object, in relation to its parent object, if
* applicable. Defaults to 0. */
public var beginTime: CFTimeInterval { get set }
/* The basic duration of the object. Defaults to 0. */
public var duration: CFTimeInterval { get set }
/* The rate of the layer. Used to scale parent time to local time, e.g.
* if rate is 2, local time progresses twice as fast as parent time.
* Defaults to 1. */
public var speed: Float { get set }
/* Additional offset in active local time. i.e. to convert from parent
* time tp to active local time t: t = (tp - begin) * speed + offset.
* One use of this is to "pause" a layer by setting `speed' to zero and
* `offset' to a suitable value. Defaults to 0. */
public var timeOffset: CFTimeInterval { get set }
/* The repeat count of the object. May be fractional. Defaults to 0. */
public var repeatCount: Float { get set }
/* The repeat duration of the object. Defaults to 0. */
public var repeatDuration: CFTimeInterval { get set }
/* When true, the object plays backwards after playing forwards. Defaults
* to NO. */
public var autoreverses: Bool { get set }
/* Defines how the timed object behaves outside its active duration.
* Local time may be clamped to either end of the active duration, or
* the element may be removed from the presentation. The legal values
* are `backwards', `forwards', `both' and `removed'. Defaults to
* `removed'. */
public var fillMode: String { get set }
beginTime继承CAMediaTiming协议的对象的起始时间
duration基本动画的持续时间
speed动画的运行速度，当为0时会停止动画，speed越大说明动画执行速度越快
timeOffset动画的时间偏移，也就是上次动画的暂停/继续 距离本次动画的继续/暂停的时间差
repeatCount重复次数
repeatDuration重复的时间
autoreverses是否会回到原来的位置
fillMode
CAFillModeRemoved这个是默认值,也就是说当动画开始前和动画结束后,动画对layer都没有影响,动画结束后,layer会恢复到之前的状态
kCAFillModeForwards当动画结束后,layer会一直保持着动画最后的状态
kCAFillModeBackwards这个和kCAFillModeForwards是相对的,就是在动画开始前,你只要将动画加入了一个layer,layer便立即进入动画的初始状态并等待动画开始.你可以这样设定试代码,将一个动画加入一个layer的时候延迟5秒执行.然后就会发现在动画没有开始的时候,只要动画被加入了layer,layer便处于动画初始状态
kCAFillModeBoth理解了上面两个,这个就很好理解了,这个其实就是上面两个的合成.动画加入后开始之前,layer便处于动画初始状态,动画结束后layer保持动画最后的状态.
- 下面进行实例演习
做一个不停旋转的动画，通过点击事件控制动画的暂停或播放
///头像旋转,开始动画
fileprivate func beginAnimation() {
let rotateAnimation = CABasicAnimation(keyPath: "transform.rotation.z")
rotateAnimation.fromValue = 0
rotateAnimation.toValue = (Double.pi * 2)
rotateAnimation.duration = 20
rotateAnimation.repeatCount = MAXFLOAT
singerImageView.layer.add(rotateAnimation, forKey: "")
}
写一个CALayer的分类，控制动画的暂停与继续
extension CALayer {
///暂停动画
func pauseAnimation() {
//取出当前时间,转成动画暂停的时间
let pausedTime = self.convertTime(CACurrentMediaTime(), from: nil)
//设置动画运行速度为0
self.speed = 0.0;
//设置动画的时间偏移量，指定时间偏移量的目的是让动画定格在该时间点的位置
self.timeOffset = pausedTime
}
///恢复动画
func resumeAnimation() {
//获取暂停的时间差
let pausedTime = self.timeOffset
self.speed = 1.0
self.timeOffset = 0.0
self.beginTime = 0.0
//用现在的时间减去时间差,就是之前暂停的时间,从之前暂停的时间开始动画
let timeSincePause = self.convertTime(CACurrentMediaTime(), from: nil) - pausedTime
self.beginTime = timeSincePause
}
}
效果图如下：
animation.gif
