在执行代码之前等待 Swift 动画完成

Question

我正在尝试为 UIImageView 设置动画，然后在动画完成后隐藏图像视图。然而，图像视图在动画完成之前被隐藏。我查看了类似的问题，他们建议在完成后实现动画侦听器或在动画代码中执行 .hidden 代码，但是我不确定如何在下面的 ShakeView() 函数中影响这一点。

如何在动画完成后才显示摇动动画并隐藏图像视图？

使用以下代码调用动画：

shakeView(image1!)
shakeView(image2)
image1!.hidden = true
image2.hidden = true

动画函数本身是这样的：

func shakeView(iv: UIImageView){
    var shake:CABasicAnimation = CABasicAnimation(keyPath: "position")
    shake.duration = 0.1
    shake.repeatCount = 2
    shake.autoreverses = true

    var from_point:CGPoint = CGPointMake(iv.center.x - 5, iv.center.y)
    var from_value:NSValue = NSValue(CGPoint: from_point)

    var to_point:CGPoint = CGPointMake(iv.center.x + 5, iv.center.y)
    var to_value:NSValue = NSValue(CGPoint: to_point)

    shake.fromValue = from_value
    shake.toValue = to_value
    iv.layer.addAnimation(shake, forKey: "position")
}

Answer 1

您可以在动画完成后使用CATransaction 调用完成块。

func shakeView(iv: UIImageView){

    CATransaction.begin()
    CATransaction.setCompletionBlock({
        iv.hidden = true
    })
    var shake:CABasicAnimation = CABasicAnimation(keyPath: "position")
    shake.duration = 0.1
    shake.repeatCount = 21
    shake.autoreverses = true

    var from_point:CGPoint = CGPointMake(iv.center.x - 5, iv.center.y)
    var from_value:NSValue = NSValue(CGPoint: from_point)

    var to_point:CGPoint = CGPointMake(iv.center.x + 5, iv.center.y)
    var to_value:NSValue = NSValue(CGPoint: to_point)

    shake.fromValue = from_value
    shake.toValue = to_value
    iv.layer.addAnimation(shake, forKey: "position")
    CATransaction.commit()
}

或者您也可以将两个动画组合在CATransaction 中，如下所示。

func shakeView(iv: UIImageView){
    var shake:CABasicAnimation = CABasicAnimation(keyPath: "position")
    shake.duration = 0.1
    shake.repeatCount = 21
    shake.autoreverses = true

    var from_point:CGPoint = CGPointMake(iv.center.x - 5, iv.center.y)
    var from_value:NSValue = NSValue(CGPoint: from_point)

    var to_point:CGPoint = CGPointMake(iv.center.x + 5, iv.center.y)
    var to_value:NSValue = NSValue(CGPoint: to_point)

    shake.fromValue = from_value
    shake.toValue = to_value
    iv.layer.addAnimation(shake, forKey: "position")
}

override func viewDidLoad() {
    CATransaction.begin()

    CATransaction.setCompletionBlock({
        self.image1.hidden = true
        self.image2.hidden = true
    })
    shakeView(image1)
    shakeView(image)
  CATransaction.commit()
}

Answer 2

正如 Paulw11 在他的评论中提到的，您可以使用文档中提到的 animationDidStop: 方法。但此外，您应该为您的 CABasicAnimation/CAAnimation 对象添加一个键，以便您的 animationDidStop: 方法知道哪个特别完成了。

所以在你的shake方法中添加一个值-键对来识别动画并将代理设置为self，例如：

func shakeView(iv: UIImageView){

    var shake:CABasicAnimation = CABasicAnimation(keyPath: "position")
    shake.duration = 0.1
    shake.repeatCount = 2
    shake.autoreverses = true

    // Add these two lines:
    shake.setValue("shake", forKey: "animationID")
    shake.delegate = self

    // ...

然后添加 animationDidStop: 委托方法来提醒您动画何时完成，以便您可以开始执行代码：

override func animationDidStop(anim: CAAnimation!, finished flag: Bool) {
    // Unwrap the optional value for the key "animationID" then
    // if it's equal to the same value as the relevant animation,
    // execute the relevant code
    if let animationID: AnyObject = anim.valueForKey("animationID") {
        if animationID as NSString == "shake" {
            // execute code
        }
    }
}