检测表已在iOS 13上关闭

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？

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来通知您，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“成为最前端”检测？。

这是父视图控制器的代码示例，当其以表单形式显示（即以默认的iOS 13方式）时，通知该视图控制器：

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）原始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）。

另一个选择回来viewWillAppear并viewDidAppear设置

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

此选项全屏显示，关闭后调用上述方法

对于将来的读者，这里是实现的更完整答案：

1. 在根视图控制器中为segue做准备，添加以下内容（假设您的模态具有导航控制器）

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

2. 在模态视图控制器中，添加以下委托+方法

// 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. 确保在模式视图控制器中，以下属性为true，以便调用委托方法

    self.isModalInPresentation = true

4. 利润

迅速

一般解决呼叫 viewWillAppear在iOS13

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)
            }
        }
    }

DRAG或CALL DISMISS FUNC将与以下代码一起使用。

1）在根视图控制器中，您知道哪个是其演示视图控制器，如下代码

 override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if segue.identifier == "presenterID" {
        let navigationController = segue.destination as! UINavigationController
        if #available(iOS 13.0, *) {
            let controller = navigationController.topViewController as! presentationviewcontroller
            // Modal Dismiss iOS 13
            controller.presentationController?.delegate = self
        } else {
            // Fallback on earlier versions
        }
        navigationController.presentationController?.delegate = self

    }
}

2）再次在根视图控制器中，告诉您当演示文稿视图控制器消失时将要执行的操作

public func presentationControllerDidDismiss(
  _ presentationController: UIPresentationController)
{
    print("presentationControllerDidDismiss")
}

1）在演示视图控制器中，单击此图片中的“取消”或“保存”按钮。下面的代码将被调用。

self.dismiss(animated: true) {
        self.presentationController?.delegate?.presentationControllerDidDismiss?(self.presentationController!)
    }

覆盖正在被关闭的UIViewController上的viewWillDisappear。它将通过isBeingDismissed布尔标志提醒您被解雇。

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

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

**如果用户在中途向下滑动并向后滑动卡时，即使卡未被取消，该卡仍会注册为已被取消。但这是一个极端情况，您可能并不在意。

如果某人无权访问呈现的视图控制器，则他们可以在呈现视图控制器时重写以下方法，并将其更改modalPresentationStyle为fullScreen或可以使用此方法添加上述策略之一

 override func present(_ viewControllerToPresent: UIViewController, animated flag: Bool, completion: (() -> Void)? = nil) {
    if let _ = viewControllerToPresent as? TargetVC {
        viewControllerToPresent.modalPresentationStyle = .fullScreen
    }
    super.present(viewControllerToPresent, animated: flag, completion: completion)
}

如果显示的视图控制器是导航控制器，并且您要检查根控制器，则可以将上述条件更改为

if let _ = (viewControllerToPresent as? UINavigationController)?.viewControllers.first as? TargetVC {
   viewControllerToPresent.modalPresentationStyle = .fullScreen
}

如果在FullScreen中使用了ModalPresentationStyle，则控制器的行为将恢复为通常的状态。

ConsultarController controllerConsultar = this.Storyboard.InstantiateViewController（“ ConsultarController”）作为ConsultarController; controllerConsultar.ModalPresentationStyle = UIModalPresentationStyle.FullScreen; this.NavigationController.PushViewController（controllerConsultar，true）;

从我的角度来看，苹果不应该设置pageSheet默认modalPresentationStyle

我想fullScreen通过使用将样式恢复为默认值swizzling

像这样：

private func _swizzling(forClass: AnyClass, originalSelector: Selector, swizzledSelector: Selector) {
    if let originalMethod = class_getInstanceMethod(forClass, originalSelector),
       let swizzledMethod = class_getInstanceMethod(forClass, swizzledSelector) {
        method_exchangeImplementations(originalMethod, swizzledMethod)
    }
}

extension UIViewController {

    static func preventPageSheetPresentationStyle () {
        UIViewController.preventPageSheetPresentation
    }

    static let preventPageSheetPresentation: Void = {
        if #available(iOS 13, *) {
            _swizzling(forClass: UIViewController.self,
                       originalSelector: #selector(present(_: animated: completion:)),
                       swizzledSelector: #selector(_swizzledPresent(_: animated: completion:)))
        }
    }()

    @available(iOS 13.0, *)
    private func _swizzledPresent(_ viewControllerToPresent: UIViewController,
                                        animated flag: Bool,
                                        completion: (() -> Void)? = nil) {
        if viewControllerToPresent.modalPresentationStyle == .pageSheet
                   || viewControllerToPresent.modalPresentationStyle == .automatic {
            viewControllerToPresent.modalPresentationStyle = .fullScreen
        }
        _swizzledPresent(viewControllerToPresent, animated: flag, completion: completion)
    }
}

然后把这条线放到你的 AppDelegate

UIViewController.preventPageSheetPresentationStyle()

调用presentingViewController.viewWillAppear不是很简单吗？被解雇？

self.presentingViewController?.viewWillAppear(false)
self.dismiss(animated: true, completion: nil)