ios - 将三个动画间隔一秒的最佳方法是什么？

Question

有没有比使用 asyncAfter 三次更好的方法让这些动画间隔一秒？

let firstAnimationTime = DispatchTime.now()
let secondAnimationTime = DispatchTime.now() + 1
let thirdAnimationTime = DispatchTime.now() + 2
DispatchQueue.main.asyncAfter(deadline: firstAnimationTime) {
    self.firstAnimation()
}
DispatchQueue.main.asyncAfter(deadline: secondAnimationTime) {
    self.secondAnimation()
}
DispatchQueue.main.asyncAfter(deadline: thirdAnimationTime) {
    self.thirdAnimation()
}

Answer 1

你可以使用 UIView.animate(withDuration:delay:...)

甚至可以定义一个函数如下:

func animateSequentially(withDurations durations: [TimeInterval], animations: [(() -> Void)]) {

    guard durations.count == animations.count else {
        return
    }

    for index in 0..<animations.count {

        // calculate delay
        let delay: TimeInterval = durations[0..<index].reduce(TimeInterval(0), { delay, duration in
            return delay + duration
        })

        // perform animation
        UIView.animate(withDuration: durations[index],
                       delay: delay,
                       options: [],
                       animations: animations[index],
                       completion: nil)
    }
}

然后像这样使用:

let myView = UIView()

let durations = [1, 0.5, 1.25]

let animations = [{ myView.backgroundColor = .red },
                  { myView.backgroundColor = .yellow },
                  { myView.backgroundColor = .blue }]

animateSequentially(withDurations: durations, animations: animations)