Ios 带持续时间的Swift-CoreAnimation

试图理解CoreAnimation和完成处理程序。
为什么这段代码一次发生，而不是超过5.0秒？
我试图让它运行6次，每次持续5秒，总共30秒，并且每5秒打印一次“完成”

    func animateBox() {

        UIView.animate(withDuration: 5.0, delay: 0.0, options: [], animations: {
            self.myBox.layer.borderColor = self.getRandom()
        }, completion: {finished in
            print("complete")
        })
    
    }

    @objc func buttonTapped() {
        
        for _ in 1...6 {
            animateBox()
            print("animate")
        }
    }

---

for uu in 1…6{

立即执行，因此

animateBox

在一瞬间被调用6次，一次又一次

您要做的是调用前一个动画块的完成处理程序（动画完成时调用）中的每个动画块。类似于以下内容：

UIView.animate(withDuration: 5.0, delay: 0.0, options: [], animations: {
    self.myBox.layer.borderColor = self.getRandom()
}, completion: { finished in
    print("complete")

    UIView.animate(withDuration: 5.0, delay: 0.0, options: [], animations: {
        self.myBox.layer.borderColor = self.getRandom()
    }, completion: { finished in
        print("complete")

        UIView.animate(withDuration: 5.0, delay: 0.0, options: [], animations: {
            self.myBox.layer.borderColor = self.getRandom()
        }, completion: { finished in
            print("complete")

            ...
        })
    })
})

但这将导致一个巨大的完成金字塔…相反，请尝试使用

animateKeyframes

：

let totalDuration = CGFloat(30)
let relativeIndividualDuration = CGFloat(1) / CGFloat(6)

UIView.animateKeyframes(withDuration: totalDuration, delay: 0, options: .calculationModeCubic, animations: {
    UIView.addKeyframe(withRelativeStartTime: 0.0, relativeDuration: relativeIndividualDuration) {
        self.myBox.layer.borderColor = self.getRandom()
    }

    UIView.addKeyframe(withRelativeStartTime: relativeIndividualDuration, relativeDuration: relativeIndividualDuration) {
        self.myBox.layer.borderColor = self.getRandom()
    }

    UIView.addKeyframe(withRelativeStartTime: relativeIndividualDuration * 2, relativeDuration: relativeIndividualDuration) {
        self.myBox.layer.borderColor = self.getRandom()
    }

    ...
})

---

对动画进行排序的另一种方法是使用delay参数，并在第一步之后为每个步骤添加延迟：

func animateBox(step: Int) {
    let duration = 5.0
    UIView.animate(withDuration: duration, 
      delay: duration * Double(step), 
      options: [], 
      animations: {
        self.myBox.layer.borderColor = self.getRandom()
    }, completion: {finished in
        print("complete")
    })

}

@objc func buttonTapped() {
    
    for index in 0...5 {
        animateBox(step: index)
        print("animating step \(index)")
    }
}

（注意，我将您的循环更改为从0…5开始运行，因此

delay=step*duration

将从0开始。）