Ios CAGradientLayer颜色更改动画未执行
我正在尝试制作一个非常基本的Ios CAGradientLayer颜色更改动画未执行,ios,swift,core-graphics,caanimation,cagradientlayer,Ios,Swift,Core Graphics,Caanimation,Cagradientlayer,我正在尝试制作一个非常基本的CAGradientLayer动画。我有一个基本的2色CAGradientLayer设置,并添加到我的UIViewController // Set up the gradient layer. var gradientLayer: CAGradientLayer! { let layer = CAGradientLayer() layer.frame = self.view.bounds layer.colors = [UIColor.red
CAGradientLayer
动画。我有一个基本的2色CAGradientLayer
设置,并添加到我的UIViewController
// 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设置动画:
@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
产生任何更改。我做错了什么?您每次都从gradientLayer
属性返回一个新的层
对象。您需要对其进行一点更改,以使其惰性地启动:
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
}()
为了完整性起见,您最初拥有的是一个计算属性,这意味着每次访问它时都会执行代码。对于惰性属性,当第一次访问属性时,代码只执行一次,然后返回相同的对象
在这个操场上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