是否有与 viewWillDisappear(_:) 等效的 SwiftUI 或检测视图何时将被删除? [英] Is there a SwiftUI equivalent for viewWillDisappear(_:) or detect when a view is about to be removed?

问题描述

在 SwiftUI 中，我试图找到一种方法来检测视图即将被删除，只有在使用默认的 navigationBackButton 时.然后执行一些操作.

In SwiftUI, I'm trying to find a way to detect that a view is about to be removed only when using the default navigationBackButton. Then perform some action.

使用onDisappear(perform:)就像viewDidDisappear(_:)，动作在另一个视图出现后执行.

Using onDisappear(perform:) acts like viewDidDisappear(_:), and the action performs after another view appears.

或者，我认为可以通过检测 default navigationBarBackButton 何时被按下来解决上述问题.但我发现没有办法检测到这一点.

Or, I was thinking the above problem might be solved by detecting when the default navigationBarBackButton is pressed. But I've found no way to detect that.

是否有任何解决方案可以在另一个视图出现之前执行某些操作?

Is there any solution to perform some action before another view appears?

(我已经知道可以通过创建一个自定义导航返回按钮来关闭视图)

(I already know it is possible to do that by creating a custom navigation back button to dismiss a view)

推荐答案

这是对我有用的方法，它不是纯 SwiftUI，但我认为值得发布

Here is approach that works for me, it is not pure-SwiftUI but I assume worth posting

用法:

   SomeView()
   .onDisappear {
        print("x Default disappear")
    }
   .onWillDisappear { // << order does NOT matter
        print(">>> going to disappear")
    }

代码:

struct WillDisappearHandler: UIViewControllerRepresentable {
    func makeCoordinator() -> WillDisappearHandler.Coordinator {
        Coordinator(onWillDisappear: onWillDisappear)
    }

    let onWillDisappear: () -> Void

    func makeUIViewController(context: UIViewControllerRepresentableContext<WillDisappearHandler>) -> UIViewController {
        context.coordinator
    }

    func updateUIViewController(_ uiViewController: UIViewController, context: UIViewControllerRepresentableContext<WillDisappearHandler>) {
    }

    typealias UIViewControllerType = UIViewController

    class Coordinator: UIViewController {
        let onWillDisappear: () -> Void

        init(onWillDisappear: @escaping () -> Void) {
            self.onWillDisappear = onWillDisappear
            super.init(nibName: nil, bundle: nil)
        }

        required init?(coder: NSCoder) {
            fatalError("init(coder:) has not been implemented")
        }

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

struct WillDisappearModifier: ViewModifier {
    let callback: () -> Void

    func body(content: Content) -> some View {
        content
            .background(WillDisappearHandler(onWillDisappear: callback))
    }
}

extension View {
    func onWillDisappear(_ perform: @escaping () -> Void) -> some View {
        self.modifier(WillDisappearModifier(callback: perform))
    }
}

这篇关于是否有与 viewWillDisappear(_:) 等效的 SwiftUI 或检测视图何时将被删除?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！