选择特定视图后，如何使用生命周期方法？

问题描述

我目前正在使用SwiftUI开发应用程序。

此应用有2个视图，可控制一个标签视图。

我想用这些方法sceneDidBecomeActive和sceneWillEnterForeground在SceneDelegate.swift仅在选择的特定视图。

这些方法不管选择哪个视图都有效。

我该如何请求？

SceneDelegate.swift

import SwiftUI

class SceneDelegate: UIResponder,UIWindowSceneDelegate {
    
    var window: UIWindow?

    func scene(_ scene: UIScene,willConnectTo session: UIScenesession,options connectionoptions: UIScene.Connectionoptions) {
       
        let contentView = ContentView()

        if let windowScene = scene as? UIWindowScene {
            let window = UIWindow(windowScene: windowScene)
            window.rootViewController = UIHostingController(rootView: contentView)
            self.window = window
            window.makeKeyAndVisible()
        }
    }
    func sceneDiddisconnect(_ scene: UIScene) {
    }
    func sceneDidBecomeActive(_ scene: UIScene) {
        // I want use this print method only when FirstView is selected
        print("selected FirstVIew")
    }
    func sceneWillResignActive(_ scene: UIScene) {
    }
    func sceneWillEnterForeground(_ scene: UIScene) {
        // I want use this print method only when FirstView is selected
        print("selected FirstVIew")
    }
    func sceneDidEnterBackground(_ scene: UIScene) {
    }
}

ContentView.swift

import SwiftUI

struct ContentView: View {
    
   var body: some View {
        TabView {
           FirstView()
                .tabItem {
                        Text("First")
            }.tag(1)
           SecondView()
                .tabItem {
                        Text("Second")
            }.tag(2)
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

FirstView.swift

import SwiftUI

struct FirstView: View {
    var body: some View {
        Text("FirstView")
    }
}

struct FirstView_Previews: PreviewProvider {
    static var previews: some View {
        FirstView()
    }
}

SecondView.swift

import SwiftUI

struct SecondView: View {
    var body: some View {
        Text("SecondView")
    }
}

struct SecondView_Previews: PreviewProvider {
    static var previews: some View {
        SecondView()
    }
}

Xcode：版本11.7

Swift：Swift 5

解决方法

SceneDelegate方法处理App的生命周期，而不是视图的生命周期。因此，选择视图后，您将无法“运行”它们。

尽管可以使用UserDefaults。

// When first view selected
UserDefaults.standard.set("First View",forKey: "selectedView")

// In SceneDelegate
func sceneDidBecomeActive(_ scene: UIScene) {
    if let selected = UserDefaults.standard.string(forKey: "selectedView"),selected == "First View" {
        print("selected FirstVIew")
    }
}

func sceneWillEnterForeground(_ scene: UIScene) {
    if let selected = UserDefaults.standard.string(forKey: "selectedView"),selected == "First View" {
        print("selected FirstVIew")
    }
}

swift5 swiftui