检测表已在iOS 13上关闭

Question

在iOS 13之前，提供了用于覆盖整个屏幕的视图控制器。并且，在关闭后，将viewDidAppear执行父视图控制器功能。

现在，iOS 13默认将表单显示为视图控制器，这意味着卡将部分覆盖基础视图控制器，这意味着viewDidAppear不会被调用，因为父视图控制器从未真正消失过。

有没有一种方法可以检测到所显示的视图控制器工作表已被解雇？我可以在父视图控制器中重写某些其他功能，而不是使用某种委托？

Answer 1

有没有一种方法可以检测到所显示的视图控制器工作表已被解雇？

是。

我可以在父视图控制器中重写某些其他功能，而不是使用某种委托？

不，“某种委托”是您的工作方式。使自己成为演示控制器的委托和重写presentationControllerDidDismiss(_:)。

https://developer.apple.com/documentation/uikit/uiadaptivepresentationcontrollerdelegate/3229889-presentationcontrollerdiddismiss

缺少一个一般的运行时生成的事件，通知您所显示的视图控制器（无论是否为全屏）已被关闭，这确实很麻烦。但这不是一个新问题，因为始终存在非全屏显示的视图控制器。只是现在（在iOS 13中）有更多！我在其他地方对此主题进行了单独的问答：统一UIViewController“成为最前面的”检测工具？。

Answer 2

另一个取回viewWillAppear并viewDidAppear设置的选项

let vc = UIViewController()
vc.modalPresentationStyle = .fullScreen

此选项全屏显示，关闭后调用上述方法

Answer 3

这是父视图控制器的代码示例，该子视图在子视图控制器呈现为工作表时（即，以默认的iOS 13方式）被通知时通知：

public final class Parent: UIViewController, UIAdaptivePresentationControllerDelegate
{
  // This is assuming that the segue is a storyboard segue; 
  // if you're manually presenting, just see the delegate there.
  public override func prepare(for segue: UIStoryboardSegue, sender: Any?)
  {
    if segue.identifier == "mySegue" {
      segue.destination.presentationController?.delegate = self;
    }
  }

  public func presentationControllerDidDismiss(
    _ presentationController: UIPresentationController)
  {
    // Only called when the sheet is dismissed by DRAGGING.
    // You'll need something extra if you call .dismiss() on the child.
    // (I found that overriding dismiss in the child and calling
    // presentationController.delegate?.presentationControllerDidDismiss
    // works well).
  }
}

Jerland2的答案很混乱，因为（a）最初的提问者想在关闭工作表时获得一个函数调用（而他实现了presentationControllerDidAttemptToDismiss，当用户尝试并无法关闭工作表时会调用它），并且（b）设置isModalInPresentation是完全正交的，实际上会使所呈现的图纸不可忽略（这与OP想要的相反）。

Answer 4

如果您想在用户从该工作表中关闭模式工作表时执行某些操作。假设您已经有一些“关闭”按钮，其中包含一个@IBAction在关闭或执行其他操作之前显示警报的逻辑。您只想检测用户按下此类控制器的时刻。

就是这样：

class MyModalSheetViewController: UIViewController {

     override func viewDidLoad() {
        super.viewDidLoad()

        self.presentationController?.delegate = self
     }

     @IBAction func closeAction(_ sender: Any) {
         // your logic to decide to close or not, when to close, etc.
     }

}

extension MyModalSheetViewController: UIAdaptivePresentationControllerDelegate {

    func presentationControllerShouldDismiss(_ presentationController: UIPresentationController) -> Bool {
        return false // <-prevents the modal sheet from being closed
    }

    func presentationControllerDidAttemptToDismiss(_ presentationController: UIPresentationController) {
        closeAction(self) // <- called after the modal sheet was prevented from being closed and leads to your own logic
    }
}

Answer 5

For future readers here is a more complete answer with implementation:

1. In the root view controllers prepare for segue add the following (Assuming your modal has a nav controller)

    // Modal Dismiss iOS 13
    modalNavController.presentationController?.delegate = modalVc

2. In the modal view controller add the following delegate + method

// MARK: - iOS 13 Modal (Swipe to Dismiss)

extension ModalViewController: UIAdaptivePresentationControllerDelegate {
    func presentationControllerDidAttemptToDismiss(_ presentationController: UIPresentationController) {


        print("slide to dismiss stopped")
        self.dismiss(animated: true, completion: nil)
    }
}

3. Ensure in the modal View Controller that the following property is true in order for the delegate method to be called

    self.isModalInPresentation = true

4. Profit

Answer 6

覆盖正在被驳回的viewWillDisappear内容UIViewController。它会通过布尔标志提醒您解雇isBeingDismissed。

override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)

    if isBeingDismissed {
        print("user is dismissing the vc")
    }
}

** 如果用户向下滑动一半并向上滑动卡片，即使卡片没有被关闭，它仍然会注册为被关闭。但这是您可能不关心的极端情况。

Answer 7

迅速

viewWillAppear在iOS13 中调用的一般解决方案

class ViewController: UIViewController {

        override func viewWillAppear(_ animated: Bool) {
            super.viewWillAppear(animated)
            print("viewWillAppear")
        }

        //Show new viewController
        @IBAction func show(_ sender: Any) {
            let newViewController = NewViewController()
            //set delegate of UIAdaptivePresentationControllerDelegate to self
            newViewController.presentationController?.delegate = self
            present(newViewController, animated: true, completion: nil)
        }
    }

    extension UIViewController: UIAdaptivePresentationControllerDelegate {
        public func presentationControllerDidDismiss( _ presentationController: UIPresentationController) {
            if #available(iOS 13, *) {
                //Call viewWillAppear only in iOS 13
                viewWillAppear(true)
            }
        }
    }