如何在Swift中下一个动画开始之前等待一个动画完成？

Question

如何在Swift中下一个动画开始之前等待一个动画完成？我一直在乱搞if animation.animationDidStop... {},但它不会起作用.

这是我目前的一些代码:

class ViewController: UIViewController {
@IBOutlet weak var purpleRing: UIImageView!
@IBOutlet weak var beforeCountdownAnimation: UIImageView!

var imageArray = [UIImage]()
var imageArray2 = [UIImage]()

override func viewDidLoad() {
    super.viewDidLoad()

    for e in -17...0 {
    let imageName2 = "\(e)"
        imageArray2.append(UIImage(named: imageName2)!)
    }

    for t in 1...97 {
        let imageName = "\(t)"
        imageArray.append(UIImage(named: imageName)!)
    }
}

func startAnimation() -> Void {
    purpleRing.animationImages = imageArray
    purpleRing.animationDuration = 5.0
    purpleRing.startAnimating()
}

func startAnimation2() -> Void {
    beforeCountdownAnimation.animationImages = imageArray2
    beforeCountdownAnimation.animationDuration = 1.0
    beforeCountdownAnimation.startAnimating()
}

@IBAction func startAnimations(sender: AnyObject) {
    startAnimation()
    startAnimation2()
}

Answer 1

嗯，可能之前回答过，但您可以使用 Grand Central Dispatch dispatc_aysnc。

这个想法是，您知道动画持续时间，因此您可以用它来告诉 GDC 何时执行下一个代码。所以像这样：

// call animation 1, which you specified to have 5 second duration
CGFloat animation1Duration = 5.0;
CGFloat animation2Duration = 7.0;

playAnimation1WithDuration(animation1Duration);

// calling second animation block of code after 5.0 using GDC
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, Int64(animation1Duration * Double(NSEC_PER_SEC))), dispatch_get_main_queue(), { () -> Void in

    print("5.0 has passed");

    // call second animation block here
    playAnimation2WithDuration(animation2Duration);

});