当呈现的视图控制器被手势关闭时如何得到通知？

Question

在某些情况下（iPhone X，iOS 13）可以通过从顶部拉动手势来关闭呈现的视图控制器。

在那种情况下，我似乎找不到通知呈现视图控制器的方法。我错过了什么吗？

我发现的唯一方法是向呈现的视图控制器的 viewDidDisappear 添加委托方法。

类似于：

class Presenting: UIViewController, PresentedDelegate {
    func someAction() {
        let presented = Presented()
        presented.delegate = self
        present(presented, animated: true, completion: nil)
    }
    func presentedDidDismiss(_ presented: Presented) {
        // Presented was dismissed
    }
}

protocol PresentedDelegate: AnyObject {
    func presentedDidDismiss(_ presented: Presented)
}

class Presented: UIViewController {
    weak var delegate: PresentedDelegate?

    override func viewDidDisappear(animated: Bool) {
         ...
         delegate?.presentedDidDismiss(self)
    }
}

也可以使用 vc 子类通过通知来管理它，但仍然不能令人满意。


extension Notification.Name {
    static let viewControllerDidDisappear = Notification.Name("UIViewController.viewControllerDidDisappear")
}

open class NotifyingViewController: UIViewController {

    override open func viewDidDisappear(_ animated: Bool) {
        super.viewDidDisappear(animated)

        NotificationCenter.default.post(name: .viewControllerDidDisappear, object: self)
    }
}

一定有更好的方法吗？

Answer 1

采用UIAdaptivePresentationControllerDelegate并实施presentationControllerDidAttemptToDismiss (iOS 13+)

extension Presenting : UIAdaptivePresentationControllerDelegate {

    func presentationControllerDidAttemptToDismiss(_ presentationController: UIPresentationController) {
       presentationController.presentingViewController.presentedDidDismiss(self)
    }
}

UIPresentationController 有一个属性 presentingViewController。这个名字是不言自明的。您不需要显式委托协议。

实际调用该方法是为了能够显示一个对话框，例如在关闭控制器之前保存更改。您还可以实施 presentationControllerDidDismiss()

并且不要 post 向彼此相关的控制器发送通知。这是不好的做法。

Answer 2

来自 iOS13 Apple 为用户引入了一种新方法 dismiss 通过从顶部向下拉呈现的视图控制器。可以通过将 UIAdaptivePresentationControllerDelegate 实现到您正在呈现的 UIViewController 来捕获此事件，在本例中为 Presenting 控制器。然后您可以在方法 presentationControllerDidDismiss 中收到有关此事件的通知。这是代码示例：-

class Presenting: UIViewController, UIAdaptivePresentationControllerDelegate {

    func someAction() {
        let presented = Presented()
        presented.presentationController?.delegate = self
        present(presented, animated: true, completion: nil)
    }

    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).
    }
}

注：

此方法仅在通过从顶部滑动而关闭时触发，而不是程序化 dismiss(animated:,completion:) 方法。
您不需要任何自定义委托或 Notification 观察器来获取用户通过向下滑动关闭控制器的事件，因此您可以删除它们。

当呈现的视图控制器被手势关闭时如何得到通知？

How to get notified when a presented view controller is dismissed with a gesture?

uiviewcontroller

ios

swift