检测表在 iOS 13 上被取消

Question

在 iOS 13 之前，呈现用于覆盖整个屏幕的视图控制器。并且，当关闭时，父视图控制器viewDidAppear 函数被执行。

现在 iOS 13 将默认将视图控制器呈现为工作表，这意味着卡片将部分覆盖底层视图控制器，这意味着 viewDidAppear 将不会被调用，因为父视图控制器从未真正消失过。

有没有办法检测呈现的视图控制器工作表已被解除？我可以在父视图控制器中覆盖其他一些功能而不是使用某种委托？

Answer 1

有没有办法检测呈现的视图控制器工作表已被解除？

是的。

我可以在父视图控制器中覆盖其他一些功能，而不是使用某种委托？

没有。 “某种代表”就是你的做法。让自己成为演示控制器的代表并覆盖 presentationControllerDidDismiss(_:)。

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

---

缺少一个通用的运行时生成的事件来通知您呈现的视图控制器（无论是否全屏）已被解除，这确实很麻烦；但这不是一个新问题，因为一直存在非全屏呈现的视图控制器。只是现在（在 iOS 13 中）还有更多！我在别处专门针对此主题单独问答：Unified UIViewController "became frontmost" detection?。

Answer 2

这是一个父视图控制器的代码示例，当它作为工作表呈现的子视图控制器（即，以默认的 iOS 13 方式）被关闭时会收到通知：

public final class Parent: UIViewController, UIAdaptivePresentationControllerDelegate
{
  // This is assuming that the segue is a storyboard segue; 
  // if you're manually presenting, just set 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 的回答令人困惑，因为 (a) 最初的提问者希望在工作表被关闭 时获得一个函数调用（而他实现了presentationControllerDidAttemptToDismiss，当用户尝试和未能关闭工作表），并且（b）设置 isModalInPresentation 是完全正交的，实际上会使呈现的工作表不可关闭（这与 OP 想要的相反）。

Answer 3

设置了返回viewWillAppear 和viewDidAppear 的另一个选项

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

此选项覆盖全屏，关闭后调用上述方法

Answer 4

对于未来的读者，这里有一个更完整的实施答案：

1. 在根视图控制器准备 segue 添加以下内容（假设您的模态有一个导航控制器）

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

1. 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)
    }
}

1. 确保在模态视图控制器中以下属性为真，以便调用委托方法

    self.isModalInPresentation = true

4. 利润

Answer 5

斯威夫特

在iOS13中调用viewWillAppear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)
            }
        }
    }

Answer 6

在被解除的UIViewController 上覆盖viewWillDisappear。它会通过 isBeingDismissed 布尔标志提醒您解雇。

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

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

** 如果用户在向下滑动一半的过程中再次向上滑动卡片，即使卡片没有被关闭，它仍然会注册为被关闭。但这是你可能不关心的边缘情况。

Answer 7

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。 假设您已经有一些带有@IBAction 的关闭按钮和一个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。

方法如下：

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 8

DRAG OR CALL DISMISS FUNC 将使用以下代码。

1) 在根视图控制器中，您可以通过下面的代码告诉它哪个是其表示视图控制器

 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，你告诉当它的展示视图控制器被释放时你会做什么

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

1) 在演示视图控制器中，当您点击这张图片中的取消或保存按钮时。下面的代码将被调用。

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

Answer 9

在 SwiftUI 中你可以使用 onDismiss 闭包

func sheet<Item, Content>(item: Binding<Item?>, onDismiss: (() -> Void)?, content: (Item) -> Content) -> some View

Answer 10

如果有人无权访问呈现的视图控制器，他们可以在呈现视图控制器中覆盖以下方法并将modalPresentationStyle更改为fullScreen，或者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)
}

如果呈现的视图控制器是导航控制器并且您想检查根控制器，可以将上述条件更改为类似

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

Answer 11

如果您在 FullScreen 中使用 ModalPresentationStyle，则控制器的行为将恢复正常。

ConsultarController controllerConsultar = this.Storyboard.InstantiateViewController("ConsultarController") as ConsultarController; controllerConsultar.ModalPresentationStyle = UIModalPresentationStyle.FullScreen; this.NavigationController.PushViewController(controllerConsultar, true);

Answer 12

在我看来，苹果不应该将pageSheet设置为默认modalPresentationStyle

我想使用 swizzling 将 fullScreen 样式恢复为默认样式

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)
    }
}

然后把这行写到你的AppDelegate

UIViewController.preventPageSheetPresentationStyle()

Answer 13

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

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