How to animate borderColor change in swift

问题:

For some reason this isn't working for me:

let color = CABasicAnimation(keyPath: "borderColor")
color.fromValue = sender.layer.borderColor;
color.toValue = UIColor.redColor().CGColor;
color.duration = 2;
color.repeatCount = 1;
sender.layer.addAnimation(color, forKey: "color and width");

I'm not getting any animation to occur.

回答1:

You have to use the same key name. You also forgot to add a border width and color to your layer before animating it. Try like this:

let color = CABasicAnimation(keyPath: "borderColor")

@IBAction func animateBorder(sender: AnyObject) {
    color.fromValue = UIColor.greenColor().CGColor
    color.toValue = UIColor.redColor().CGColor
    color.duration = 2
    color.repeatCount = 1
    sender.layer.borderWidth = 2
    sender.layer.borderColor = UIColor.greenColor().CGColor
    sender.layer.addAnimation(color, forKey: "borderColor")
}

回答2:

I don't know why, but for some reason calling:

color.fromValue = sender.layer.borderColor

doesn't work. The color isn't being read correctly or something. I changed it to:

let color = CABasicAnimation(keyPath: "borderColor");
color.fromValue = UIColor.greenColor().CGColor;
color.toValue = UIColor.redColor().CGColor;
color.duration = 2;
color.repeatCount = 1;
sender.layer.addAnimation(color, forKey: "color and width");

And then things started working as expected.

回答3:

Swift 4 UIView extension:

extension UIView {
  func animateBorderColor(toColor: UIColor, duration: Double) {
    let animation:CABasicAnimation = CABasicAnimation(keyPath: "borderColor")
    animation.fromValue = layer.borderColor
    animation.toValue = toColor.cgColor
    animation.duration = duration
    layer.add(animation, forKey: "borderColor")
    layer.borderColor = toColor.cgColor
  }
}

And then just use it by writing:

myView.animateBorderColor(toColor: .red, duration: 0.5)

回答4:

I created a Swift 4 function extension to CALayer for this, to which you can pass the starting and ending UIColors as well as the duration for the animation:

extension CALayer {

func animateBorderColor(from startColor: UIColor, to endColor: UIColor, withDuration duration: Double) {
    let colorAnimation = CABasicAnimation(keyPath: "borderColor")
    colorAnimation.fromValue = startColor.cgColor
    colorAnimation.toValue = endColor.cgColor
    colorAnimation.duration = duration
    self.borderColor = endColor.cgColor
    self.add(colorAnimation, forKey: "borderColor")
}

Note that for this to work, you should have already set a borderWidth and then call animateBorderColor:

yourView.layer.borderWidth = 1.5
yourView.layer.animateBorderColor(from: UIColor.green, to: UIColor.red, withDuration: 2.0)