我正在尝试使一个非常基本的CAGradientLayer
动画起作用。我设置了一个基本的2色CAGradientLayer
,并将其添加到我的UIViewController
中。
// Set up the gradient layer.
var gradientLayer: CAGradientLayer! {
let layer = CAGradientLayer()
layer.frame = self.view.bounds
layer.colors = [UIColor.redColor().CGColor, UIColor.yellowColor().CGColor]
layer.locations = [0.0, 1.0]
return layer
}
我正在尝试使用以下代码制作动画:
@IBAction func changeBackground(sender: AnyObject) {
let oldColors = self.gradientLayer.colors
let newColors = [UIColor.purpleColor().CGColor, UIColor.blueColor().CGColor]
self.gradientLayer.colors = newColors
let animation: CABasicAnimation = CABasicAnimation(keyPath: "colors")
animation.fromValue = oldColors
animation.toValue = newColors
animation.duration = 0.3
animation.removedOnCompletion = true
animation.fillMode = kCAFillModeForwards
animation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionLinear)
animation.delegate = self
self.gradientLayer.addAnimation(animation, forKey: "animateGradientColorChange")
}
但是,此代码不会对
CAGradientLayer
进行任何更改。我在这里做错了什么? 最佳答案
每次都从layer
属性返回一个新的gradientLayer
对象。您需要对其进行一些更改,以便使其延迟启动:
lazy var gradientLayer: CAGradientLayer! = {
let layer = CAGradientLayer()
layer.frame = self.view.bounds
layer.colors = [UIColor.redColor().CGColor, UIColor.yellowColor().CGColor]
layer.locations = [0.0, 1.0]
return layer
}()
为了完整起见,您最初拥有的是一个计算属性,这意味着该代码在您每次访问时都会执行。使用惰性属性,当第一次访问该属性然后返回相同的对象时,该代码仅执行一次。
在这个游乐场可以观察到不同之处:
//: Playground - noun: a place where people can play
import UIKit
struct Dummy {
var gradientLayer: CAGradientLayer! {
let layer = CAGradientLayer()
layer.colors = [UIColor.redColor().CGColor, UIColor.yellowColor().CGColor]
layer.locations = [0.0, 1.0]
return layer
}
lazy var lazyGradientLayer: CAGradientLayer! = {
let layer = CAGradientLayer()
layer.colors = [UIColor.redColor().CGColor, UIColor.yellowColor().CGColor]
layer.locations = [0.0, 1.0]
return layer
}()
}
var dummy = Dummy()
let l1 = dummy.gradientLayer
let l2 = dummy.gradientLayer
let lazy1 = dummy.lazyGradientLayer
let lazy2 = dummy.lazyGradientLayer
关于ios - CAGradientLayer颜色更改动画未执行,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/38562195/