用程序化的方式让我的过渡经理知道我从哪里来或要去哪里？迅捷

Question

所以，我在我的animateTransition func里有这段代码，如果我试图借助包含这个func的transitionManager来展示一个viewcontroller，它就找不到from view。

    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
      // Getting the reference to container, toView & fromView
      let container = transitionContext.containerView
      let fromView = transitionContext.view(forKey: .from)! // Force unpacked
      let toView = transitionContext.view(forKey: .to)! // Force unpacked

      // Setup for the 2d animation
      let offScreenRight = CGAffineTransform(translationX: container.frame.width, y: 0)
      let offScreenLeft = CGAffineTransform(translationX: -container.frame.width, y: 0)

      // Start the toView to the right of the screen
      container.addSubview(toView)
      container.addSubview(fromView)

      // Get the duration of the animation
      let duration = self.transitionDuration(using: transitionContext)

      // Perform the animation
      UIView.animate(withDuration: duration, delay: 0.0, usingSpringWithDamping: 0.5, initialSpringVelocity: 0.8, animations: {

        fromView.transform = offScreenLeft
        toView.transform = .identity

      }, completion: { finished in

        // Tell our transitionContext object that we've finished animating
        transitionContext.completeTransition(true)
      })

    }

如果我试图用TransitionManager的帮助来展示一个viewcontroller, 它包含了这个func, 它找不到from view. 如果我想解散，它找不到to view。我怎样才能告诉它从现在的哪里来，怎样才能告诉它在解散时要去哪里？

Answer 1

好了，我找到了解决方案。我之所以不能根据 dismiss 或 present 来获取 fromView 或 toView 的引用，是因为我调用了：UIViewControllerContextTransitioning。

let fromView = transitionContext.view(forKey: .from)! 
let toView = transitionContext.view(forKey: .to)!

我应该调用：

let fromView = transitionContext.viewController(forkey: .from)!.view!
let toView = transitionContext.viewController(forkey: .to)!.view!