如何在执行segue之前执行按钮动画[重复]

Posted 2023-02-27

【中文标题】如何在执行segue之前执行按钮动画[重复]

【英文标题】：How to perform button animation before performing segue [duplicate]

【发布时间】：2018-12-27 17:05:01

【问题描述】：

在我的主屏幕中，我有一个 startGame 按钮，按下该按钮时会触发动画 (sender.pulsate())，然后还会更改 viewController：

 @IBAction func newGamePressed(_ sender: UIButton) 
        currentScore = 0
        timeRemaining = 60
        visualTime = "01:00"

        sender.pulsate()

        let storyboard = UIStoryboard(name: "Main", bundle: nil)
        let viewController = storyboard.instantiateViewController(withIdentifier: "firstLevel")
        self.present(viewController, animated: false, completion: nil)

    

但是，新的 viewController 会立即出现，而不是等待脉动动画发生（脉动动画确实有效）。

我知道这与没有自上而下阅读的代码有关，但是我可以添加什么来告诉 xcode 在另一个之前运行一个？

谢谢！

ps。这是相关的脉动代码：

   func pulsate() 

        let pulse = CASpringAnimation(keyPath: "transform.scale")
        pulse.duration = 0.6
        pulse.fromValue = 0.95
        pulse.toValue = 1.0
        pulse.autoreverses = true
        pulse.repeatCount = 2
        pulse.initialVelocity = 0.5
        pulse.damping = 1.0

        layer.add(pulse, forKey: nil)

    

【参考方案1】：

您的动画持续时间为0.6 秒。在那之后展示 ViewController

---

之后异步

您可以为您的 pulsate 方法创建完成，该方法在动画结束后执行

func pulsate(duration: CFTimeInterval, _ completion: @escaping ()->()) 
    ...
    pulse.duration = duration
    ...
    DispatchQueue.main.asyncAfter(deadline: .now() + duration) 
        completion()
    

---

CATransaction 的完成块

您可以为您的pulsate 方法创建completion，该方法在您的CAAnimation 结束后执行。为此，您可以使用CATransaction 的完成块

func pulsate(duration: CFTimeInterval, _ completion: @escaping ()->()) 
    CATransaction.begin()
    ...
    pulse.duration = duration
    ...
    CATransaction.setCompletionBlock 
        completion()
    
    CATransaction.commit()

---

sender.pulsate(duration: 0.6) 
    let storyboard = UIStoryboard(name: "Main", bundle: nil)
    let viewController = storyboard.instantiateViewController(withIdentifier: "firstLevel")
    self.present(viewController, animated: false, completion: nil)

【讨论】：

感谢这个成功！

【参考方案2】：

也可以使用performSelector来实现

 @IBAction func didTapButton(_ sender: UIButton) 
        let animationDuration = 0.6
        sender.pulsate(duration:animationDuration)

        //Invoke method after particular delay on current thread

        self.perform(#selector(navigateToViewController), with: nil, afterDelay: animationDuration)
 

 @objc func navigateToViewController() 
        let storyboard = UIStoryboard(name: "Main", bundle: nil)
        let viewController = storyboard.instantiateViewController(withIdentifier: "NewViewControllerID") as! NewViewController
        self.present(viewController, animated: false, completion: nil)
 

脉动码

func pulsate(duration: Double) 

    let pulse = CASpringAnimation(keyPath: "transform.scale")
    pulse.duration = duration
    pulse.fromValue = 0.95
    pulse.toValue = 1.0
    pulse.autoreverses = true
    pulse.repeatCount = 2
    pulse.initialVelocity = 0.5
    pulse.damping = 1.0

    layer.add(pulse, forKey: nil)   

【参考方案3】：

只需对我们的动画使用完成方法，没有计时器延迟。

func pulsate() 
    let pulse = CASpringAnimation(keyPath: "transform.scale")
    pulse.duration = 0.6
    pulse.fromValue = 0.95
    pulse.toValue = 1.0
    pulse.autoreverses = true
    pulse.repeatCount = 2
    pulse.initialVelocity = 0.5
    pulse.damping = 1.0
    layer.add(pulse, forKey: nil)

    CATransaction.setCompletionBlock 
        print("animation done")
        let storyboard = UIStoryboard(name: "Main", bundle: nil)
    let viewController = storyboard.instantiateViewController(withIdentifier:        "firstLevel")
    self.present(viewController, animated: false, completion: nil)
    

【讨论】：

请注意，这不起作用，因为他的pulsate 方法在UIButton 上被调用并且按钮不能present ViewController

【参考方案4】：

使用asyncAfter 和[weak self] 的替代方法来删除保留周期，

DispatchQueue.main.asyncAfter(deadline: .now() + 0.6)  [weak self] in
    self?.present(viewController, animated: false, completion: nil)

【讨论】：

什么是保留周期？

保持对对方对象的强引用，会导致内存泄漏