取消UIViewPropertyAnimator动画后UIKit安全区域计算异常问题

场景描述 #

使用UIViewPropertyAnimator实现视图从初始帧CGRect(x: 10, y: 10, width: 100, height: 100)到目标帧CGRect(x: 10, y: 10, width: 300, height: 300)的动画，并添加了动画过程中暂停并反向取消的功能。首次取消动画时，视图帧与安全区域布局帧匹配；但第二次取消时，视图帧已重置为初始值，safeAreaLayoutGuide.layoutFrame的宽度却仍保持300，二者无法同步。

实现代码 #

启动动画的代码 #

@objc func onTap() {
    animator = UIViewPropertyAnimator(duration: 3, curve: .easeIn)
    
    animator.addAnimations {
      self.testView.frame = CGRect(x: 10, y: 10, width: 300, height: 300)
    }
    
    animator.addCompletion { pos in
      print("test view frame:::", self.testView.frame)
      print("test view safe frame:::", self.testView.safeAreaLayoutGuide.layoutFrame)
      print("test view safe inset:::", self.testView.safeAreaInsets)
      print("test view keyboard frame:::", self.testView.keyboardLayoutGuide.layoutFrame)
    }
    animator.startAnimation()
}

暂停并取消动画的代码 #

@objc func cancelTheAnimation() {
    animator.pauseAnimation()
    animator.isReversed = true
    
    let progress = animator.fractionComplete
    
    animator.continueAnimation(
      withTimingParameters: UICubicTimingParameters(animationCurve: .linear),
      durationFactor: 1 - progress)
}

控制台输出 #

------- animation completion ------
test view frame::: (10.0, 10.0, 100.0, 100.0)
test view safe frame::: (0.0, 37.0, 100.0, 63.0)
test view safe inset::: UIEdgeInsets(top: 37.0, left: 0.0, bottom: 0.0, right: 0.0)
test view keyboard frame::: (-10.0, 100.0, 390.0, 734.0)
------- animation completion ------
test view frame::: (10.0, 10.0, 100.0, 100.0)
test view safe frame::: (0.0, 37.0, 300.0, 263.0)
test view safe inset::: UIEdgeInsets(top: 37.0, left: 0.0, bottom: 0.0, right: 0.0)
test view keyboard frame::: (-10.0, 300.0, 390.0, 534.0)

疑问 #

这是UIKit的bug吗？如果不是，该如何修复才能让安全区域布局帧与视图帧同步？

内容的提问来源于stack exchange，提问作者Reyshawn