动画 CAShapeLayer / CAGradientLayer

Question

这是对我昨天提出的问题的补充。结果完美，但我想要修改。

下面的代码，基于上面的线程，生成了一个 CABasicAnimation 来生成深蓝色 "triangle." 我希望它不是深蓝色纯色，而是一个有 3 个色标的 CAGradientLayer： Red /绿色/蓝色。

我尝试添加一个 CAGradientLayer 来配置渐变，然后使用 addSubLayer 将渐变添加到动画出来的 CAShapeLayer。我在下面发布的结果没有动画。颜色和形状保持不变。渐变看起来不错，只需要它动画出来：

import UIKit
import QuartzCore
import XCPlayground

let view = UIView(frame: CGRect(x: 0, y: 0, width: 521, height: 40))
view.backgroundColor = UIColor.whiteColor()
XCPlaygroundPage.currentPage.liveView = view

let maskPath = UIBezierPath()

maskPath.moveToPoint(CGPoint(x: 0, y: 30))
maskPath.addLineToPoint(CGPoint(x: 0, y: 25))
maskPath.addLineToPoint(CGPoint(x: 300, y: 10))
maskPath.addLineToPoint(CGPoint(x: 300, y: 30))
maskPath.closePath()

let maskLayer = CAShapeLayer()
maskLayer.path = maskPath.CGPath
maskLayer.fillColor = UIColor.whiteColor().CGColor

let rectToAnimateFrom = UIBezierPath(rect: CGRect(x: 0, y: 0, width: 0, height: 40))
let rectToAnimateTo = UIBezierPath(rect: CGRect(x: 0, y: 0, width: 97, height: 40))

let backgroundGray = CAShapeLayer()
backgroundGray.path = maskPath.CGPath
backgroundGray.fillColor = UIColor.grayColor().CGColor

let foregroundGradient = CAShapeLayer()
foregroundGradient.mask = maskLayer
foregroundGradient.backgroundColor = UIColor.clearColor().CGColor


let gradientLayer = CAGradientLayer()
gradientLayer.startPoint = CGPointMake(0, 0)
gradientLayer.endPoint = CGPointMake(1, 0)
gradientLayer.frame = maskPath.bounds

let colors = [UIColor.redColor().CGColor, UIColor.greenColor().CGColor, UIColor.blueColor().CGColor]
gradientLayer.colors = colors


foregroundGradient.addSublayer(gradientLayer)


view.layer.addSublayer(backgroundGray)
view.layer.addSublayer(foregroundGradient)


let animation = CABasicAnimation(keyPath: "path")
animation.fromValue = rectToAnimateFrom.CGPath
animation.toValue = rectToAnimateTo.CGPath
animation.duration = 2
animation.removedOnCompletion = false
animation.fillMode = kCAFillModeForwards


foregroundGradient.addAnimation(animation, forKey: nil)

我需要 foregroundGradient 对象（带有 gradientLayer 子层！）从左到右设置动画。

如果您从我上面的代码中删除渐变，并将 foregroundGradient 保留为纯色，您将看到动画效果。

Answer 1

我认为您必须在您的视图中使用您的 mask，如下所述。

//Remove below line
view.layer.addSublayer(backgroundGray)

//Add your mask to view
view.layer.mask = backgroundGray

整个函数如下所示：

func getGradientView() {
    let view = UIView(frame: CGRect(x: 0, y: 50, width: 521, height: 40))
    view.backgroundColor = UIColor.grayColor()
    self.view.addSubview(view)

    let maskPath = UIBezierPath()

    maskPath.moveToPoint(CGPoint(x: 0, y: 30))
    maskPath.addLineToPoint(CGPoint(x: 0, y: 25))
    maskPath.addLineToPoint(CGPoint(x: 300, y: 10))
    maskPath.addLineToPoint(CGPoint(x: 300, y: 30))
    maskPath.closePath()

    let maskLayer = CAShapeLayer()
    maskLayer.path = maskPath.CGPath
    maskLayer.fillColor = UIColor.whiteColor().CGColor

    let rectToAnimateFrom = UIBezierPath(rect: CGRect(x: 0, y: 0, width: 0, height: 40))
    let rectToAnimateTo = UIBezierPath(rect: CGRect(x: 0, y: 0, width: 300, height: 40))

    let backgroundGray = CAShapeLayer()
    backgroundGray.path = maskPath.CGPath
    backgroundGray.fillColor = UIColor.grayColor().CGColor

    let foregroundGradient = CAShapeLayer()
    foregroundGradient.mask = maskLayer
    foregroundGradient.backgroundColor = UIColor.clearColor().CGColor


    let gradientLayer = CAGradientLayer()
    gradientLayer.startPoint = CGPointMake(0, 0)
    gradientLayer.endPoint = CGPointMake(1, 0)
    gradientLayer.frame = maskPath.bounds

    let colors = [UIColor.redColor().CGColor, UIColor.greenColor().CGColor, UIColor.blueColor().CGColor]
    gradientLayer.colors = colors

    foregroundGradient.addSublayer(gradientLayer)

    //Remove below line
    //view.layer.addSublayer(backgroundGray)

    view.layer.addSublayer(foregroundGradient)

    //Add you mask to view
    view.layer.mask = backgroundGray

    let animation = CABasicAnimation(keyPath: "path")
    animation.fromValue = rectToAnimateFrom.CGPath
    animation.toValue = rectToAnimateTo.CGPath
    animation.duration = 1
    animation.repeatCount = 1000
    animation.removedOnCompletion = false
    animation.fillMode = kCAFillModeForwards


    maskLayer.addAnimation(animation, forKey: "fill animation")
}

让我知道它是否按照您的例外情况工作。

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