Question

我在UIView的动画中使用了这个场景没有任何问题，但是无法使用CALayer动画。

我做了一个游乐场来证明这个问题：

import UIKit
import PlaygroundSupport

class EventHandler {
    @objc func onClick(_ button: UIButton) {

        button.layer.removeAllAnimations()

        button.layer.borderColor = UIColor.red.cgColor
        print("RED")

        CATransaction.begin()
        CATransaction.setCompletionBlock({
            button.layer.borderColor = UIColor.black.cgColor
            print("BLACK")
        })

        let colorAnimation = CABasicAnimation()
        colorAnimation.toValue = UIColor.black.cgColor
        colorAnimation.duration = 5
        button.layer.add(colorAnimation, forKey: "borderColor")
        CATransaction.commit()

    }
}

let eventHandler = EventHandler()

let button = UIButton(frame: CGRect.init(x: 0, y: 0, width: 200, height: 200))

button.backgroundColor = UIColor.gray
button.layer.borderColor = UIColor.black.cgColor
button.layer.borderWidth = 20
button.addTarget(eventHandler, action: #selector(EventHandler.onClick(_:)), for: .touchDown)

PlaygroundPage.current.liveView = button

我想要的是当我点击动画中间的按钮时，动画应该重新开始。但似乎当我调用removeAllAnimations（）时，原始动画的完成块不会在我将颜色设置为RED之后执行，而是在它之后执行。

Answer 1

通过将fromValue设置为动画对象来解决此问题。这是工作版本：

import UIKit
import PlaygroundSupport

class EventHandler {
    @objc func onClick(_ button: UIButton) {

        button.layer.removeAllAnimations()

        let colorAnimation = CABasicAnimation()
        colorAnimation.fromValue = UIColor.red.cgColor
        colorAnimation.toValue = UIColor.black.cgColor
        colorAnimation.duration = 5
        button.layer.add(colorAnimation, forKey: "borderColor")   
    }
}

let eventHandler = EventHandler()

let button = UIButton(frame: CGRect.init(x: 0, y: 0, width: 200, height: 200))

button.backgroundColor = UIColor.gray
button.layer.borderColor = UIColor.black.cgColor
button.layer.borderWidth = 20
button.addTarget(eventHandler, action: #selector(EventHandler.onClick(_:)), for: .touchDown)

PlaygroundPage.current.liveView = button

如何在CALayer动画进行中重新启动？

1 个答案: