ios - 核心动画——修改动画属性

Question

我有动画

 func startRotate360() {
    let rotation : CABasicAnimation = CABasicAnimation(keyPath: "transform.rotation.z")
    rotation.fromValue = 0
    rotation.toValue =  Double.pi * 2
    rotation.duration = 1
    rotation.isCumulative = true
    rotation.repeatCount = Float.greatestFiniteMagnitude
    self.layer.add(rotation, forKey: "rotationAnimation")
}

我想要的是能够通过将其重复计数设置为 1 来停止动画，从而完成当前旋转(简单地删除动画是不行的，因为它看起来不太好)

我试着跟随

func stopRotate360() {
    self.layer.animation(forKey: "rotationAnimation")?.repeatCount = 1
}

但是我崩溃了并且在控制台中

attempting to modify read-only animation

如何访问可写属性？

Answer 1

试一试。实际上，您可以更改正在进行的 CAAnimations。有很多方法。这是最快/最简单的。您甚至可以完全停止动画并在用户不注意的情况下继续播放。

您可以看到开始动画功能和停止功能。开始动画看起来与您的类似，而停止从表示层获取当前旋转并创建动画以旋转直到完成。我还将持续时间平滑为完成基于当前旋转 z 到基于运行动画的完整旋转所需时间的百分比。然后我删除带有重复计数的动画并添加新动画。您可以看到 View 平滑地旋转到最终位置并停止。你会明白的。将其放入并运行它，看看您的想法。点击按钮开始并再次点击以查看它完成旋转并停止。

import UIKit

class ViewController: UIViewController {

    var animationView = UIView()
    var button = UIButton()

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.

        animationView = UIView(frame: CGRect(x: 0, y: 0, width: 200, height: 200))
        animationView.backgroundColor = .green
        animationView.center = view.center
        self.view.addSubview(animationView)

        let label = UILabel(frame: animationView.bounds)
        label.text = "I Spin"
        animationView.addSubview(label)


        button = UIButton(frame: CGRect(x: 20, y: animationView.frame.maxY + 60, width: view.bounds.width - 40, height: 40))
        button.setTitle("Animate", for: .normal)
        button.setTitleColor(.blue, for: .normal)
        button.addTarget(self, action: #selector(ViewController.pressed), for: .touchUpInside)
        self.view.addSubview(button)

    }

    func pressed(){

        if let title = button.titleLabel?.text{
            let trans = CATransition()
            trans.type = "rippleEffect"
            trans.duration = 0.6
            button.layer.add(trans, forKey: nil)

            switch title {
            case "Animate":
                //perform animation
                button.setTitle("Stop And Finish", for: .normal)
                rotateAnimationRepeat()
                break
            default:
                //stop and finish
                button.setTitle("Animate", for: .normal)
                stopAnimationAndFinish()
                break
            }
        }

    }

    func rotateAnimationRepeat(){
        //just to be sure because of how i did the project
        animationView.layer.removeAllAnimations()
        let rotation : CABasicAnimation = CABasicAnimation(keyPath: "transform.rotation.z")
        rotation.fromValue = 0
        rotation.toValue =  Double.pi * 2
        rotation.duration = 0.5
        rotation.repeatCount = Float.greatestFiniteMagnitude
        //not doing cumlative
        animationView.layer.add(rotation, forKey: "rotationAnimation")
    }

    func stopAnimationAndFinish(){
        if let presentation = animationView.layer.presentation(){
            if let currentRotation = presentation.value(forKeyPath: "transform.rotation.z") as? CGFloat{

                var duration = 0.5

                //smooth out duration for change
                duration = Double((CGFloat(Double.pi * 2) - currentRotation))/(Double.pi * 2)
                animationView.layer.removeAllAnimations()

                let rotation : CABasicAnimation = CABasicAnimation(keyPath: "transform.rotation.z")
                rotation.fromValue = currentRotation
                rotation.toValue = Double.pi * 2
                rotation.duration = duration * 0.5
                animationView.layer.add(rotation, forKey: "rotationAnimation")

            }
        }
    }
}

结果: