Swift-动画过渡重复

Question

我已经实现了两个图像视图，如下所示：

图像完全相同。我想使用.repeat选项从右到左制作动画，因此它永远不会完成。该代码可以正常工作，但是问题是当我尝试在后台运行应用程序后恢复动画状态时。动画仍在继续，但是就像图像2将会完成，然后只有背景，而没有图像（照片＃2）。

viewDidLoad方法：

secondImage.transform = CGAffineTransform.identity.translatedBy(x: +self.view.bounds.width + 440, y: 0)
NotificationCenter.default.addObserver(self, selector: #selector(self.didEnterBackground), name: .UIApplicationDidEnterBackground, object: nil)
NotificationCenter.default.addObserver(self, selector: #selector(self.didEnterForeground), name: NSNotification.Name.UIApplicationWillEnterForeground, object: nil)

didEnterBackground方法

firstImageTransform = firstImage.layer.presentation()?.affineTransform() ?? .identity
secondImageTransform = secondImage.layer.presentation()?.affineTransform() ?? .identity

didEnterForeground方法

self.firstImage.transform = firstImageTransform
 self.secondImage.transform = CGAffineTransform.identity.translatedBy(x: +(self.firstImage.frame.origin.x + self.firstImage.frame.width ), y: 0)
 self.animate()

动画方法

UIView.animate(withDuration: 15, delay: 0, options: [.repeat, .beginFromCurrentState, .curveLinear], animations: { [unowned self] in
       var transform = self.firstImage.transform
       transform = transform.concatenating(CGAffineTransform(translationX: -(self.view.bounds.width + 440), y: 0))
       self.firstImage.transform = transform

       var transformSecond = self.secondImage.transform
       transformSecond = transformSecond.concatenating(CGAffineTransform(translationX: -(self.view.bounds.width + 440), y: 0))
       self.secondImage.transform = transformSecond }, completion: nil)