SwiftUI：如何弹出到根视图

Question

现在终于有了 Beta 5，我们可以通过编程方式弹出到父视图。但是，在我的应用程序中有几个地方的视图有一个“保存”按钮，该按钮结束了几个步骤并返回到开头。在 UIKit 中，我使用了 popToRootViewController()，但我一直无法找到在 SwiftUI 中执行相同操作的方法。

下面是我试图实现的模式的一个简单示例。有什么想法吗？

import SwiftUI

struct DetailViewB: View {
    @Environment(\.presentationMode) var presentationMode: Binding<PresentationMode>
    var body: some View {
        VStack {
            Text("This is Detail View B.")

            Button(action: { self.presentationMode.value.dismiss() } )
            { Text("Pop to Detail View A.") }

            Button(action: { /* How to do equivalent to popToRootViewController() here?? */ } )
            { Text("Pop two levels to Master View.") }

        }
    }
}

struct DetailViewA: View {
    @Environment(\.presentationMode) var presentationMode: Binding<PresentationMode>
    var body: some View {
        VStack {
            Text("This is Detail View A.")

            NavigationLink(destination: DetailViewB() )
            { Text("Push to Detail View B.") }

            Button(action: { self.presentationMode.value.dismiss() } )
            { Text("Pop one level to Master.") }
        }
    }
}

struct MasterView: View {
    var body: some View {
        VStack {
            Text("This is Master View.")

            NavigationLink(destination: DetailViewA() )
            { Text("Push to Detail View A.") }
        }
    }
}

struct ContentView: View {
    var body: some View {
        NavigationView {
            MasterView()
        }
    }
}

Answer 1

在NavigationLink 上将视图修饰符isDetailLink 设置为false 是使pop-to-root 工作的关键。 isDetailLink 默认为true 并自适应于包含视图。例如，在 iPad 横向上，拆分视图是分开的，isDetailLink 确保目标视图将显示在右侧。将isDetailLink 设置为false 因此意味着目标视图将始终被推送到导航堆栈上；因此可以随时弹出。

在将NavigationLink 上的isDetailLink 设置为false 的同时，将isActive 绑定传递给每个后续目标视图。最后，当你想弹出根视图时，将值设置为false，它会自动弹出所有内容：

import SwiftUI

struct ContentView: View {
    @State var isActive : Bool = false

    var body: some View {
        NavigationView {
            NavigationLink(
                destination: ContentView2(rootIsActive: self.$isActive),
                isActive: self.$isActive
            ) {
                Text("Hello, World!")
            }
            .isDetailLink(false)
            .navigationBarTitle("Root")
        }
    }
}

struct ContentView2: View {
    @Binding var rootIsActive : Bool

    var body: some View {
        NavigationLink(destination: ContentView3(shouldPopToRootView: self.$rootIsActive)) {
            Text("Hello, World #2!")
        }
        .isDetailLink(false)
        .navigationBarTitle("Two")
    }
}

struct ContentView3: View {
    @Binding var shouldPopToRootView : Bool

    var body: some View {
        VStack {
            Text("Hello, World #3!")
            Button (action: { self.shouldPopToRootView = false } ){
                Text("Pop to root")
            }
        }.navigationBarTitle("Three")
    }
}

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

Answer 2

当然，@malhal 拥有解决方案的关键，但对我来说，将 Binding 作为参数传递给 View 是不切实际的。正如@Imthath 所指出的，环境是一种更好的方式。

这是模仿 Apple 发布的 dismiss() 方法以弹出到上一个视图的另一种方法。

定义环境的扩展：

struct RootPresentationModeKey: EnvironmentKey {
    static let defaultValue: Binding<RootPresentationMode> = .constant(RootPresentationMode())
}

extension EnvironmentValues {
    var rootPresentationMode: Binding<RootPresentationMode> {
        get { return self[RootPresentationModeKey.self] }
        set { self[RootPresentationModeKey.self] = newValue }
    }
}

typealias RootPresentationMode = Bool

extension RootPresentationMode {
    
    public mutating func dismiss() {
        self.toggle()
    }
}

用法：

1. 将.environment(\.rootPresentationMode, self.$isPresented) 添加到根NavigationView，其中isPresented 是Bool，用于表示 第一个子视图。

2. 将.navigationViewStyle(StackNavigationViewStyle()) 修饰符添加到根NavigationView，或将.isDetailLink(false) 添加到第一个子视图的NavigationLink。

3. 将@Environment(\.rootPresentationMode) private var rootPresentationMode 添加到应该执行pop to root 的任何子视图。

4. 最后，从该子视图调用self.rootPresentationMode.wrappedValue.dismiss() 将弹出到根视图。

我已经在 GitHub 上发布了一个完整的工作示例：

https://github.com/Whiffer/SwiftUI-PopToRootExample

Answer 3

由于目前 SwiftUI 仍然在后台使用 UINavigationController，因此也可以调用其popToRootViewController(animated:) 函数。您只需像这样搜索 UINavigationController 的视图控制器层次结构：

struct NavigationUtil {
  static func popToRootView() {
    findNavigationController(viewController: UIApplication.shared.windows.filter { $0.isKeyWindow }.first?.rootViewController)?
      .popToRootViewController(animated: true)
  }

  static func findNavigationController(viewController: UIViewController?) -> UINavigationController? {
    guard let viewController = viewController else {
      return nil
    }

    if let navigationController = viewController as? UINavigationController {
      return navigationController
    }

    for childViewController in viewController.children {
      return findNavigationController(viewController: childViewController)
    }

    return nil
  }
}

并像这样使用它：

struct ContentView: View {
    var body: some View {
      NavigationView { DummyView(number: 1) }
    }
}

struct DummyView: View {
  let number: Int

  var body: some View {
    VStack(spacing: 10) {
      Text("This is view \(number)")
      NavigationLink(destination: DummyView(number: number + 1)) {
        Text("Go to view \(number + 1)")
      }
      Button(action: { NavigationUtil.popToRootView() }) {
        Text("Or go to root view!")
      }
    }
  }
}

Answer 4

女士们，先生们，介绍 Apple 解决这个问题的方法。 *也通过 HackingWithSwift 呈现给你（我从 lol 偷来的）：under programmatic navigation

（在 Xcode 12 和 iOS 14 上测试）

基本上你在navigationlink 中使用tag 和selection 直接进入你想要的任何页面。

struct ContentView: View {
@State private var selection: String? = nil

var body: some View {
    NavigationView {
        VStack {
            NavigationLink(destination: Text("Second View"), tag: "Second", selection: $selection) { EmptyView() }
            NavigationLink(destination: Text("Third View"), tag: "Third", selection: $selection) { EmptyView() }
            Button("Tap to show second") {
                self.selection = "Second"
            }
            Button("Tap to show third") {
                self.selection = "Third"
            }
        }
        .navigationBarTitle("Navigation")
    }
}
}

您可以使用注入ContentView() 的@environmentobject 来处理选择：

class NavigationHelper: ObservableObject {
    @Published var selection: String? = nil
}

注入应用：

@main
struct YourApp: App {
    var body: some Scene {
        WindowGroup {
            ContentView().environmentObject(NavigationHelper())
        }
    }
}

并使用它：

struct ContentView: View {
@EnvironmentObject var navigationHelper: NavigationHelper

var body: some View {
    NavigationView {
        VStack {
            NavigationLink(destination: Text("Second View"), tag: "Second", selection: $navigationHelper.selection) { EmptyView() }
            NavigationLink(destination: Text("Third View"), tag: "Third", selection: $navigationHelper.selection) { EmptyView() }
            Button("Tap to show second") {
                self.navigationHelper.selection = "Second"
            }
            Button("Tap to show third") {
                self.navigationHelper.selection = "Third"
            }
        }
        .navigationBarTitle("Navigation")
    }
}
}

要返回子导航链接中的内容视图，您只需设置navigationHelper.selection = nil。

请注意，如果您不想，您甚至不必为后续的子导航链接使用标签和选择 - 但它们将没有转到特定导航链接的功能。

Answer 5

我花了最后几个小时试图解决同样的问题。据我所见，目前的 beta 5 没有简单的方法。我发现的唯一方法是非常 hacky 但有效。 基本上将发布者添加到您的 DetailViewA 中，该发布者将从 DetailViewB 触发。在 DetailViewB 中关闭视图并通知发布者，他自己将关闭 DetailViewA。

    struct DetailViewB: View {
    @Environment(\.presentationMode) var presentationMode: Binding<PresentationMode>
    var publisher = PassthroughSubject<Void, Never>()

    var body: some View {
        VStack {
            Text("This is Detail View B.")

            Button(action: { self.presentationMode.value.dismiss() } )
            { Text("Pop to Detail View A.") }

            Button(action: {
                DispatchQueue.main.async {
                self.presentationMode.wrappedValue.dismiss()
                self.publisher.send()
                }
            } )
            { Text("Pop two levels to Master View.") }

        }
    }
}

struct DetailViewA: View {
    @Environment(\.presentationMode) var presentationMode: Binding<PresentationMode>
    var publisher = PassthroughSubject<Void, Never>()

    var body: some View {
        VStack {
            Text("This is Detail View A.")

            NavigationLink(destination: DetailViewB(publisher:self.publisher) )
            { Text("Push to Detail View B.") }

            Button(action: { self.presentationMode.value.dismiss() } )
            { Text("Pop one level to Master.") }
        }
        .onReceive(publisher, perform: { _ in
            DispatchQueue.main.async {
                print("Go Back to Master")
                self.presentationMode.wrappedValue.dismiss()
            }
        })
    }
}

[更新] 我仍在努力，因为在最后一个 Beta 6 上仍然没有解决方案。

我找到了另一种返回根目录的方法，但这次我失去了动画，直接回到根目录。 这个想法是强制刷新根视图，这样会导致导航堆栈的清理。

但最终只有 Apple 才能提供合适的解决方案，因为导航堆栈的管理在 SwiftUI 中不可用。

注意：下面通过通知的简单解决方案适用于 iOS 而不是 watchOS，因为 watchOS 在 2 个导航级别后会从内存中清除根视图。但是有一个外部类来管理 watchOS 的状态应该可以正常工作。

struct DetailViewB: View {
    @Environment(\.presentationMode) var presentationMode: Binding<PresentationMode>

    @State var fullDissmiss:Bool = false
    var body: some View {
        SGNavigationChildsView(fullDissmiss: self.fullDissmiss){
            VStack {
                Text("This is Detail View B.")

                Button(action: { self.presentationMode.wrappedValue.dismiss() } )
                { Text("Pop to Detail View A.") }

                Button(action: {
                    self.fullDissmiss = true
                } )
                { Text("Pop two levels to Master View with SGGoToRoot.") }
            }
        }
    }
}

struct DetailViewA: View {
    @Environment(\.presentationMode) var presentationMode: Binding<PresentationMode>

    @State var fullDissmiss:Bool = false
    var body: some View {
        SGNavigationChildsView(fullDissmiss: self.fullDissmiss){
            VStack {
                Text("This is Detail View A.")

                NavigationLink(destination: DetailViewB() )
                { Text("Push to Detail View B.") }

                Button(action: { self.presentationMode.wrappedValue.dismiss() } )
                { Text("Pop one level to Master.") }

                Button(action: { self.fullDissmiss = true } )
                { Text("Pop one level to Master with SGGoToRoot.") }
            }
        }
    }
}

struct MasterView: View {
    var body: some View {
        VStack {
            Text("This is Master View.")
            NavigationLink(destination: DetailViewA() )
            { Text("Push to Detail View A.") }
        }
    }
}

struct ContentView: View {

    var body: some View {
        SGRootNavigationView{
            MasterView()
        }
    }
}
#if DEBUG
struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}
#endif

struct SGRootNavigationView<Content>: View where Content: View {
    let cancellable = NotificationCenter.default.publisher(for: Notification.Name("SGGoToRoot"), object: nil)

    let content: () -> Content

    init(@ViewBuilder content: @escaping () -> Content) {
        self.content = content
    }

    @State var goToRoot:Bool = false

    var body: some View {
        return
            Group{
            if goToRoot == false{
                NavigationView {
                content()
                }
            }else{
                NavigationView {
                content()
                }
            }
            }.onReceive(cancellable, perform: {_ in
                DispatchQueue.main.async {
                    self.goToRoot.toggle()
                }
            })
    }
}

struct SGNavigationChildsView<Content>: View where Content: View {
    let notification = Notification(name: Notification.Name("SGGoToRoot"))

    var fullDissmiss:Bool{
        get{ return false }
        set{ if newValue {self.goToRoot()} }
    }

    let content: () -> Content

    init(fullDissmiss:Bool, @ViewBuilder content: @escaping () -> Content) {
        self.content = content
        self.fullDissmiss = fullDissmiss
    }

    var body: some View {
        return Group{
            content()
        }
    }

    func goToRoot(){
        NotificationCenter.default.post(self.notification)
    }
}

Answer 6

花了一些时间，但我想出了如何在 swiftui 中使用复杂的导航。 诀窍是收集视图的所有状态，以判断它们是否显示。

首先定义一个 NavigationController。我已经添加了 tabview 选项卡的选择和表示是否显示特定视图的布尔值

import SwiftUI
final class NavigationController: ObservableObject  {

  @Published var selection: Int = 1

  @Published var tab1Detail1IsShown = false
  @Published var tab1Detail2IsShown = false

  @Published var tab2Detail1IsShown = false
  @Published var tab2Detail2IsShown = false
}

使用两个选项卡设置 tabview 并将 NavigationController.selection 绑定到 tabview：

import SwiftUI
struct ContentView: View {

  @EnvironmentObject var nav: NavigationController

  var body: some View {

    TabView(selection: self.$nav.selection){

            FirstMasterView() 
            .tabItem {
                 Text("First")
            }
            .tag(0)

           SecondMasterView() 
            .tabItem {
                 Text("Second")
            }
            .tag(1)
        }
    }
}

例如，这是一个导航堆栈

import SwiftUI


struct FirstMasterView: View {

    @EnvironmentObject var nav: NavigationController

   var body: some View {
      NavigationView{
        VStack{

          NavigationLink(destination: FirstDetailView(), isActive: self.$nav.tab1Detail1IsShown) {
                Text("go to first detail")
            }
        } .navigationBarTitle(Text("First MasterView"))
     }
  }
}

struct FirstDetailView: View {

   @EnvironmentObject var nav: NavigationController
   @Environment(\.presentationMode) var presentationMode: Binding<PresentationMode>

 var body: some View {

    VStack(spacing: 20) {
        Text("first detail View").font(.title)


        NavigationLink(destination: FirstTabLastView(), isActive: self.$nav.tab1Detail2IsShown) {
            Text("go to last detail on nav stack")
        }

        Button(action: {
            self.nav.tab2Detail1IsShown = false //true will go directly to detail
            self.nav.tab2Detail2IsShown = false 

            self.nav.selection = 1
        }) { Text("Go to second tab")
        }
    }
        //in case of collapsing all the way back
        //there is a bug with the environment object
        //to go all the way back I have to use the presentationMode
        .onReceive(self.nav.$tab1Detail2IsShown, perform: { (out) in
            if out ==  false {
                 self.presentationMode.wrappedValue.dismiss()
            }
        })
    }
 }


struct FirstTabLastView: View {
   @EnvironmentObject var nav: NavigationController

   var body: some View {
       Button(action: {
           self.nav.tab1Detail1IsShown = false
           self.nav.tab1Detail2IsShown = false
       }) {Text("Done and go back to beginning of navigation stack")
       }
   }
}

我希望我能解释一下这种方法，它非常面向 SwiftUI 状态。

Answer 7

对我来说，为了实现对 swiftUI 中仍然缺少的导航的完全控制，我只是将 SwiftUI 视图嵌入到 UINavigationController 中。在SceneDelegate 内。请注意，我隐藏导航栏是为了将 NavigationView 用作我的显示。

class SceneDelegate: UIResponder, UIWindowSceneDelegate {

    var window: UIWindow?

    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {

        UINavigationBar.appearance().tintColor = .black

        let contentView = OnBoardingView()
        if let windowScene = scene as? UIWindowScene {
            let window = UIWindow(windowScene: windowScene)
            let hostingVC = UIHostingController(rootView: contentView)
            let mainNavVC = UINavigationController(rootViewController: hostingVC)
            mainNavVC.navigationBar.isHidden = true
            window.rootViewController = mainNavVC
            self.window = window
            window.makeKeyAndVisible()
        }
    }
}

然后我创建了这个协议和扩展，HasRootNavigationController

import SwiftUI
import UIKit

protocol HasRootNavigationController {
    var rootVC:UINavigationController? { get }

    func push<Content:View>(view: Content, animated:Bool)
    func setRootNavigation<Content:View>(views:[Content], animated:Bool)
    func pop(animated: Bool)
    func popToRoot(animated: Bool)
}

extension HasRootNavigationController where Self:View {

    var rootVC:UINavigationController? {
        guard let scene = UIApplication.shared.connectedScenes.first,
            let sceneDelegate = scene as? UIWindowScene,
            let rootvc = sceneDelegate.windows.first?.rootViewController
                as? UINavigationController else { return nil }
        return rootvc
    }

    func push<Content:View>(view: Content, animated:Bool = true) {
        rootVC?.pushViewController(UIHostingController(rootView: view), animated: animated)
    }

    func setRootNavigation<Content:View>(views: [Content], animated:Bool = true) {
        let controllers =  views.compactMap { UIHostingController(rootView: $0) }
        rootVC?.setViewControllers(controllers, animated: animated)
    }

    func pop(animated:Bool = true) {
        rootVC?.popViewController(animated: animated)
    }

    func popToRoot(animated: Bool = true) {
        rootVC?.popToRootViewController(animated: animated)
    }
}

在那之后，在我的 SwiftUI 视图中，我使用/实现了 HasRootNavigationController 协议和扩展

extension YouSwiftUIView:HasRootNavigationController {

    func switchToMainScreen() {
        self.setRootNavigation(views: [MainView()])
    }

    func pushToMainScreen() {
         self.push(view: [MainView()])
    }

    func goBack() {
         self.pop()
    }

    func showTheInitialView() {
         self.popToRoot()
    }
}

这是我的代码的要点，以防我有一些更新。 https://gist.github.com/michaelhenry/945fc63da49e960953b72bbc567458e6

Answer 8

这是我使用 onAppear 的缓慢、动画、有点粗糙的向后弹出解决方案，适用于 XCode 11 和 iOS 13.1：

import SwiftUI
import Combine


struct NestedViewLevel3: View {
    @Binding var resetView:Bool
    @Environment(\.presentationMode) var presentationMode: Binding<PresentationMode>

    var body: some View {
        VStack {
            Spacer()
            Text("Level 3")
            Spacer()
            Button(action: {
                self.presentationMode.wrappedValue.dismiss()
            }) {
                Text("Back")
                    .padding(.horizontal, 15)
                    .padding(.vertical, 2)
                    .foregroundColor(Color.white)
                    .clipped(antialiased: true)
                    .background(
                        RoundedRectangle(cornerRadius: 20)
                            .foregroundColor(Color.blue)
                            .frame(minWidth: 0, maxWidth: .infinity, minHeight: 0, maxHeight: 40, alignment: .center)
                )}
            Spacer()
            Button(action: {
                self.$resetView.wrappedValue = true
                self.presentationMode.wrappedValue.dismiss()
            }) {
                Text("Reset")
                    .padding(.horizontal, 15)
                    .padding(.vertical, 2)
                    .foregroundColor(Color.white)
                    .clipped(antialiased: true)
                    .background(
                        RoundedRectangle(cornerRadius: 20)
                            .foregroundColor(Color.blue)
                            .frame(minWidth: 0, maxWidth: .infinity, minHeight: 0, maxHeight: 40, alignment: .center)
                )}
            Spacer()
        }
        .navigationBarBackButtonHidden(false)
        .navigationBarTitle("Level 3", displayMode: .inline)
        .onAppear(perform: {print("onAppear level 3")})
        .onDisappear(perform: {print("onDisappear level 3")})

    }
}

struct NestedViewLevel2: View {
    @Binding var resetView:Bool
    @Environment(\.presentationMode) var presentationMode: Binding<PresentationMode>

    var body: some View {
        VStack {
            Spacer()
            NavigationLink(destination: NestedViewLevel3(resetView:$resetView)) {
                Text("To level 3")
                    .padding(.horizontal, 15)
                    .padding(.vertical, 2)
                    .foregroundColor(Color.white)
                    .clipped(antialiased: true)
                    .background(
                        RoundedRectangle(cornerRadius: 20)
                            .foregroundColor(Color.gray)
                            .frame(minWidth: 0, maxWidth: .infinity, minHeight: 0, maxHeight: 40, alignment: .center)
                )
                    .shadow(radius: 10)
            }
            Spacer()
            Text("Level 2")
            Spacer()
            Button(action: {
                self.presentationMode.wrappedValue.dismiss()
            }) {
                Text("Back")
                    .padding(.horizontal, 15)
                    .padding(.vertical, 2)
                    .foregroundColor(Color.white)
                    .clipped(antialiased: true)
                    .background(
                        RoundedRectangle(cornerRadius: 20)
                            .foregroundColor(Color.blue)
                            .frame(minWidth: 0, maxWidth: .infinity, minHeight: 0, maxHeight: 40, alignment: .center)
                )}
            Spacer()
        }
        .navigationBarBackButtonHidden(false)
        .navigationBarTitle("Level 2", displayMode: .inline)
        .onAppear(perform: {
            print("onAppear level 2")
            if self.$resetView.wrappedValue {
                self.presentationMode.wrappedValue.dismiss()
            }
        })
        .onDisappear(perform: {print("onDisappear level 2")})
    }
}

struct NestedViewLevel1: View {
    @Binding var resetView:Bool
    @Environment(\.presentationMode) var presentationMode: Binding<PresentationMode>

    var body: some View {
        VStack {
            Spacer()
            NavigationLink(destination: NestedViewLevel2(resetView:$resetView)) {
                Text("To level 2")
                    .padding(.horizontal, 15)
                    .padding(.vertical, 2)
                    .foregroundColor(Color.white)
                    .clipped(antialiased: true)
                    .background(
                        RoundedRectangle(cornerRadius: 20)
                            .foregroundColor(Color.gray)
                            .frame(minWidth: 0, maxWidth: .infinity, minHeight: 0, maxHeight: 40, alignment: .center)
                )
                    .shadow(radius: 10)
            }
            Spacer()
            Text("Level 1")
            Spacer()
            Button(action: {
                self.presentationMode.wrappedValue.dismiss()
            }) {
                Text("Back")
                    .padding(.horizontal, 15)
                    .padding(.vertical, 2)
                    .foregroundColor(Color.white)
                    .clipped(antialiased: true)
                    .background(
                        RoundedRectangle(cornerRadius: 20)
                            .foregroundColor(Color.blue)
                            .frame(minWidth: 0, maxWidth: .infinity, minHeight: 0, maxHeight: 40, alignment: .center)
                )}
            Spacer()
        }
        .navigationBarBackButtonHidden(false)
        .navigationBarTitle("Level 1", displayMode: .inline)
        .onAppear(perform: {
            print("onAppear level 1")
            if self.$resetView.wrappedValue {
                self.presentationMode.wrappedValue.dismiss()
            }
        })
        .onDisappear(perform: {print("onDisappear level 1")})
    }
}

struct RootViewLevel0: View {
    @Binding var resetView:Bool
    var body: some View {
        NavigationView {
        VStack {
            Spacer()
            NavigationLink(destination: NestedViewLevel1(resetView:$resetView)) {
            Text("To level 1")
                .padding(.horizontal, 15)
                .padding(.vertical, 2)
                .foregroundColor(Color.white)
                .clipped(antialiased: true)
                .background(
                    RoundedRectangle(cornerRadius: 20)
                    .foregroundColor(Color.gray)
                    .frame(minWidth: 0, maxWidth: .infinity, minHeight: 0, maxHeight: 40, alignment: .center)
                )
                .shadow(radius: 10)
        }
            //.disabled(false)
            //.hidden()
            Spacer()

            }
    }
        //.frame(width:UIScreen.main.bounds.width,height:  UIScreen.main.bounds.height - 110)
        .navigationBarTitle("Root level 0", displayMode: .inline)
        .navigationBarBackButtonHidden(false)
        .navigationViewStyle(StackNavigationViewStyle())
        .onAppear(perform: {
            print("onAppear root level 0")
            self.resetNavView()
        })
        .onDisappear(perform: {print("onDisappear root level 0")})

    }

    func resetNavView(){
        print("resetting objects")
        self.$resetView.wrappedValue = false
    }

}


struct ContentView: View {
    @State var resetView = false
    var body: some View {
        RootViewLevel0(resetView:$resetView)
    }
}

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

Answer 9

感谢“Malhal”为您提供@Binding 解决方案。我错过了 .isDetailLink(false) 修饰符。我从你的代码中学到的。

就我而言，我不想在每个后续视图中都使用@Binding。

所以这是我使用 EnvironmentObject 的解决方案。

第 1 步：创建一个AppState ObservableObject

import SwiftUI
import Combine

class AppState: ObservableObject {
    @Published var moveToDashboard: Bool = false
}

第 2 步：创建 AppState 的实例并在 SceneDelegate

中添加 contentView

func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
        // Create the SwiftUI view that provides the window contents.
        let contentView = ContentView()
        let appState = AppState()

        // Use a UIHostingController as window root view controller.
        if let windowScene = scene as? UIWindowScene {
            let window = UIWindow(windowScene: windowScene)
            window.rootViewController = UIHostingController(rootView:
                contentView
                    .environmentObject(appState)
            )
            self.window = window
            window.makeKeyAndVisible()
        }
    }

第三步：ContentView.swift的代码 因此，我正在更新 Stack 中最后一个视图的 appState 值，该值使用 .onReceive() 在 contentView 中捕获，以将 NavigationLink 的 isActive 更新为 false。

这里的关键是将.isDetailLink(false) 与 NavigationLink 一起使用。否则，它将不起作用。

import SwiftUI
import Combine

class AppState: ObservableObject {
    @Published var moveToDashboard: Bool = false
}

struct ContentView: View {
    @EnvironmentObject var appState: AppState
    @State var isView1Active: Bool = false

    var body: some View {
        NavigationView {
            VStack {
                Text("Content View")
                    .font(.headline)

                NavigationLink(destination: View1(), isActive: $isView1Active) {
                    Text("View 1")
                        .font(.headline)
                }
                .isDetailLink(false)
            }
            .onReceive(self.appState.$moveToDashboard) { moveToDashboard in
                if moveToDashboard {
                    print("Move to dashboard: \(moveToDashboard)")
                    self.isView1Active = false
                    self.appState.moveToDashboard = false
                }
            }
        }
    }
}

// MARK:- View 1
struct View1: View {

    var body: some View {
        VStack {
            Text("View 1")
                .font(.headline)
            NavigationLink(destination: View2()) {
                Text("View 2")
                    .font(.headline)
            }
        }
    }
}

// MARK:- View 2
struct View2: View {
    @EnvironmentObject var appState: AppState

    var body: some View {
        VStack {
            Text("View 2")
                .font(.headline)
            Button(action: {
                self.appState.moveToDashboard = true
            }) {
                Text("Move to Dashboard")
                .font(.headline)
            }
        }
    }
}


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

Answer 10

导航视图套件 https://github.com/fatbobman/NavigationViewKit

import NavigationViewKit
NavigationView {
            List(0..<10) { _ in
                NavigationLink("abc", destination: DetailView())
            }
        }
        .navigationViewManager(for: "nv1", afterBackDo: {print("back to root") })

在 NavigationView 的任何视图中

@Environment(\.navigationManager) var nvmanager         

Button("back to root view") {
    nvmanager.wrappedValue.popToRoot(tag:"nv1"){
             print("other back")
           }
}

你也可以通过NotificationCenter调用而不在视图中调用

let backToRootItem = NavigationViewManager.BackToRootItem(tag: "nv1", animated: false, action: {})
NotificationCenter.default.post(name: .NavigationViewManagerBackToRoot, object: backToRootItem)

Answer 11

我最近创建了一个名为swiftui-navigation-stack (https://github.com/biobeats/swiftui-navigation-stack) 的开源项目。它是 SwiftUI 的替代导航堆栈。查看 README 了解所有详细信息，它真的很容易使用。

首先，如果您想在屏幕之间导航（即全屏视图），请定义您自己的简单Screen 视图：

struct Screen<Content>: View where Content: View {
    let myAppBackgroundColour = Color.white
    let content: () -> Content

    var body: some View {
        ZStack {
            myAppBackgroundColour.edgesIgnoringSafeArea(.all)
            content()
        }
    }
} 

然后将您的根嵌入NavigationStackView（就像您对标准NavigationView 所做的那样）：

struct RootView: View {
    var body: some View {
        NavigationStackView {
            Homepage()
        }
    }
}

现在让我们创建几个子视图来展示基本行为：

struct Homepage: View {
    var body: some View {
        Screen {
            PushView(destination: FirstChild()) {
                Text("PUSH FORWARD")
            }
        }
    }
}

struct FirstChild: View {
    var body: some View {
        Screen {
            VStack {
                PopView {
                    Text("JUST POP")
                }
                PushView(destination: SecondChild()) {
                    Text("PUSH FORWARD")
                }
            }
        }
    }
}

struct SecondChild: View {
    var body: some View {
        Screen {
            VStack {
                PopView {
                    Text("JUST POP")
                }
                PopView(destination: .root) {
                    Text("POP TO ROOT")
                }
            }
        }
    }
}

您可以利用PushView 和PopView 来回导航。当然你SceneDelegate里面的内容视图必须是：

// Create the SwiftUI view that provides the window contents.
let contentView = RootView()

结果是：

Answer 12

此解决方案基于 malhal 的回答，使用了 Imthath 和 Florin Odagiu 的建议，并需要 Paul Hudson 的 NavigationView 视频为我将所有内容整合在一起。这个想法很简单。当点击时，navigationLink 的 isActive 参数设置为 true。这允许出现第二个视图。您可以使用其他链接来添加更多视图。要返回根目录，只需将 isActive 设置为 false。第二个视图以及可能堆积的任何其他视图都消失了。

import SwiftUI

class Views: ObservableObject {
    @Published var stacked = false
}

struct ContentView: View {
    @ObservedObject var views = Views()
    
    var body: some View {
        NavigationView {
            NavigationLink(destination: ContentView2(), isActive: self.$views.stacked) {
                Text("Go to View 2") //Tapping this link sets stacked to true
            }
            .isDetailLink(false)
            .navigationBarTitle("ContentView")
        }
        .environmentObject(views) //Inject a new views instance into the navigation view environment so that it's available to all views presented by the navigation view. 
    }
}

struct ContentView2: View {
    
    var body: some View {
        NavigationLink(destination: ContentView3()) {
            Text("Go to View 3")
        }
        .isDetailLink(false)
        .navigationBarTitle("View 2")
    }
}

struct ContentView3: View {
    @EnvironmentObject var views: Views
    
    var body: some View {
        
        Button("Pop to root") {
            self.views.stacked = false //By setting this to false, the second view that was active is no more. Which means, the content view is being shown once again.
        }
        .navigationBarTitle("View 3")
    }
}

Answer 13

我想出了一个简单的解决方案来弹出到根视图。我正在发送通知，然后监听通知以更改 NavigationView 的 id，这将刷新 NavigationView。没有动画，但看起来不错。这里是例子：

@main
struct SampleApp: App {
    @State private var navigationId = UUID()
    
    var body: some Scene {
        WindowGroup {
            NavigationView {
                Screen1()
            }
            .id(navigationId)
            .onReceive(NotificationCenter.default.publisher(for: Notification.Name("popToRootView"))) { output in
                navigationId = UUID()
            }
        }
    }
}

struct Screen1: View {
    var body: some View {
        VStack {
            Text("This is screen 1")
            NavigationLink("Show Screen 2", destination: Screen2())            
        }
    }
}

struct Screen2: View {
    var body: some View {
        VStack {
            Text("This is screen 2")
            Button("Go to Home") {
                NotificationCenter.default.post(name: Notification.Name("popToRootView"), object: nil)
            }            
        }
    }
}

Answer 14

这是我的解决方案，可以在任何地方使用，无需依赖。

let window = UIApplication.shared.connectedScenes
  .filter { $0.activationState == .foregroundActive }
  .map { $0 as? UIWindowScene }
  .compactMap { $0 }
  .first?.windows
  .filter { $0.isKeyWindow }
  .first
let nvc = window?.rootViewController?.children.first as? UINavigationController
nvc?.popToRootViewController(animated: true)

Answer 15

iOS15 中有一个简单的解决方案，方法是使用 dismiss() 并将dismiss 传递给子视图：

struct ContentView: View {
    @State private var showingSheet = false
    var body: some View {
        NavigationView {
            Button("show sheet", action: { showingSheet.toggle()})
                .navigationTitle("ContentView")
        }.sheet(isPresented: $showingSheet) { FirstSheetView() }
    }
}

struct FirstSheetView: View {
    @Environment(\.dismiss) var dismiss
    var body: some View {
        NavigationView {
            List {
                NavigationLink(destination: SecondSheetView(dismiss: _dismiss) ) {
                    Text("show 2nd Sheet view")
                }
                NavigationLink(destination: ThirdSheetView(dismiss: _dismiss) ) {
                    Text("show 3rd Sheet view")
                }
                Button("cancel", action: {dismiss()} )
            } .navigationTitle("1. SheetView")
        }
    }
}

struct SecondSheetView: View {
    @Environment(\.dismiss) var dismiss
    var body: some View {
            List {
                NavigationLink(destination: ThirdSheetView(dismiss: _dismiss) ) {
                    Text("show 3rd SheetView")
                }
                Button("cancel", action: {dismiss()} )
            } .navigationTitle("2. SheetView")
    }
}

struct ThirdSheetView: View {
    @Environment(\.dismiss) var dismiss
    var body: some View {
            List {
                Button("cancel", action: {dismiss()} )
            } .navigationTitle("3. SheetView")
    }
}

Answer 16

我没有完全同样的问题，但我确实有代码更改根视图从不支持导航堆栈的一个到一个.诀窍是我不在 SwiftUI 中执行此操作 - 我在 SceneDelegate 中执行此操作，然后将 UIHostingController 替换为新的。

这是我的SceneDelegate 的简化摘录：

    func changeRootToOnBoarding() {
        guard let window = window else {
            return
        }

        let onBoarding = OnBoarding(coordinator: notificationCoordinator)
            .environmentObject(self)

        window.rootViewController = UIHostingController(rootView: onBoarding)
    }

    func changeRootToTimerList() {
        guard let window = window else {
            return
        }

        let listView = TimerList()
            .environmentObject(self)
        window.rootViewController = UIHostingController(rootView: listView)
    }

由于SceneDelegate 将自身置于环境中，因此任何子视图都可以添加

    /// Our "parent" SceneDelegate that can change the root view.
    @EnvironmentObject private var sceneDelegate: SceneDelegate

然后在委托上调用公共函数。我想如果你做了类似的事情，保留了View，但为它创建了一个新的UIHostingController并替换了window.rootViewController，它可能对你有用。

Answer 17

我想出了另一种可行的技术，但仍然感觉很奇怪。它仍然会为两个屏幕关闭动画，但它是一个 little 清洁器。您可以 A ) 将闭包传递到后续的详细信息屏幕或 B ) 将 detailB 传递给 detailA 的 presentationMode。这两种方法都需要关闭 detailB，然后延迟一小段时间，以便在尝试关闭 detailA 之前让 detailA 重新出现在屏幕上。

let minDelay = TimeInterval(0.001)

struct ContentView: View {
    var body: some View {
        NavigationView {
            VStack {
                NavigationLink("Push Detail A", destination: DetailViewA())
            }.navigationBarTitle("Root View")
        }
    }
}

struct DetailViewA: View {
    @Environment(\.presentationMode) var presentationMode: Binding<PresentationMode>

    var body: some View {
        VStack {
            Spacer()

            NavigationLink("Push Detail With Closure",
                           destination: DetailViewWithClosure(dismissParent: { self.dismiss() }))

            Spacer()

            NavigationLink("Push Detail with Parent Binding",
                           destination: DetailViewWithParentBinding(parentPresentationMode: self.presentationMode))

            Spacer()

        }.navigationBarTitle("Detail A")
    }

    func dismiss() {
        print ("Detail View A dismissing self.")
        presentationMode.wrappedValue.dismiss()
    }
}

struct DetailViewWithClosure: View {
    @Environment(\.presentationMode) var presentationMode: Binding<PresentationMode>

    @State var dismissParent: () -> Void

    var body: some View {
        VStack {
            Button("Pop Both Details") { self.popParent() }
        }.navigationBarTitle("Detail With Closure")
    }

    func popParent() {
        presentationMode.wrappedValue.dismiss()
        DispatchQueue.main.asyncAfter(deadline: .now() + minDelay) { self.dismissParent() }
    }
}

struct DetailViewWithParentBinding: View {
    @Environment(\.presentationMode) var presentationMode: Binding<PresentationMode>

    @Binding var parentPresentationMode: PresentationMode

    var body: some View {
        VStack {
            Button("Pop Both Details") { self.popParent() }
        }.navigationBarTitle("Detail With Binding")
    }

    func popParent() {
        presentationMode.wrappedValue.dismiss()
        DispatchQueue.main.asyncAfter(deadline: .now() + minDelay) { self.parentPresentationMode.dismiss() }
    }
}

我对 SwiftUI 的工作原理和事物的结构思考得越多，我认为 Apple 将提供与 popToRootViewController 或其他直接编辑导航堆栈等效的东西就越少。它与 SwiftUI 构建视图结构的方式背道而驰，因为它允许子视图进入父状态并对其进行操作。这正是这些方法的作用，但它们明确而公开地做到了。 DetailViewA 无法在不提供对其自身状态的访问权限的情况下创建任何一个目标视图，这意味着作者必须考虑提供所述访问权限的含义。

Answer 18

这是一种用于复杂导航的通用方法，它结合了此处描述的多种方法。如果您有许多流需要弹回根目录，而不仅仅是一个，则此模式很有用。

首先，设置您的 ObservableObject 环境，为了便于阅读，请使用枚举来键入您的视图。

class ActiveView : ObservableObject {
  @Published var selection: AppView? = nil
}

enum AppView : Comparable {
  case Main, Screen_11, Screen_12, Screen_21, Screen_22
}

[...]
let activeView = ActiveView()
window.rootViewController = UIHostingController(rootView: contentView.environmentObject(activeView))

在主 ContentView 中，在 EmptyView() 上使用带有 NavigationLink 的按钮。我们这样做是为了使用 NavigationLink 的 isActive 参数而不是标签和选择。主视图上的 Screen_11 需要在 Screen_12 上保持活动状态，相反，Screen_21 需要在 Screen_22 上保持活动状态，否则视图将弹出。不要忘记将您的 isDetailLink 设置为 false。

struct ContentView: View {
  @EnvironmentObject private var activeView: ActiveView

  var body: some View {
    NavigationView {
      VStack {
    
        // These buttons navigate by setting the environment variable. 
        Button(action: { self.activeView.selection = AppView.Screen_1.1}) {
            Text("Navigate to Screen 1.1")
        }

        Button(action: { self.activeView.selection = AppView.Screen_2.1}) {
            Text("Navigate to Screen 2.1")
        }

       // These are the navigation link bound to empty views so invisible
        NavigationLink(
          destination: Screen_11(),
          isActive: orBinding(b: self.$activeView.selection, value1: AppView.Screen_11, value2: AppView.Screen_12)) {
            EmptyView()
        }.isDetailLink(false)

        NavigationLink(
          destination: Screen_21(),
          isActive: orBinding(b: self.$activeView.selection, value1: AppView.Screen_21, value2: AppView.Screen_22)) {
            EmptyView()
        }.isDetailLink(false)
      }
    }
  }

您可以在 Screen_11 上使用相同的模式导航到 Screen_12。

现在，复杂导航的突破是 orBinding。它允许导航流上的视图堆栈保持活动状态。无论您是在 Screen_11 还是 Screen_12 上，您都需要 NavigationLink(Screen_11) 保持活动状态。

// This function create a new Binding<Bool> compatible with NavigationLink.isActive
func orBinding<T:Comparable>(b: Binding<T?>, value1: T, value2: T) -> Binding<Bool> {
  return Binding<Bool>(
      get: {
          return (b.wrappedValue == value1) || (b.wrappedValue == value2)
      },
      set: { newValue in  } // don't care the set
    )
}

Answer 19

我找到了一个适合我的解决方案。这是它的工作原理：

a gif shows how it works

在ContentView.swift 文件中：

1. 定义一个RootSelection类，声明RootSelection的@EnvironmentObject，只在根视图中记录当前活动NavigationLink的tag。
2. 为每个不是最终细节视图的NavigationLink 添加一个修饰符.isDetailLink(false)。
3. 使用文件系统层次结构来模拟NavigationView。
4. 当根视图有多个 NavigationLink 时，此解决方案可以正常工作。

import SwiftUI

struct ContentView: View {
    var body: some View {
        NavigationView {
            SubView(folder: rootFolder)
        }
    }
}

struct SubView: View {
    @EnvironmentObject var rootSelection: RootSelection
    var folder: Folder
    
    var body: some View {
        List(self.folder.documents) { item in
            if self.folder.documents.count == 0 {
                Text("empty folder")
            } else {
                if self.folder.id == rootFolder.id {
                    NavigationLink(item.name, destination: SubView(folder: item as! Folder), tag: item.id, selection: self.$rootSelection.tag)
                        .isDetailLink(false)
                } else {
                    NavigationLink(item.name, destination: SubView(folder: item as! Folder))
                        .isDetailLink(false)
                }
            }
        }
        .navigationBarTitle(self.folder.name, displayMode: .large)
        .listStyle(SidebarListStyle())
        .overlay(
            Button(action: {
                rootSelection.tag = nil
            }, label: {
                Text("back to root")
            })
            .disabled(self.folder.id == rootFolder.id)
        )
    }
}

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

class RootSelection: ObservableObject {
    @Published var tag: UUID? = nil
}

class Document: Identifiable {
    let id = UUID()
    var name: String
    
    init(name: String) {
        self.name = name
    }
}

class File: Document {}

class Folder: Document {
    var documents: [Document]
    
    init(name: String, documents: [Document]) {
        self.documents = documents
        super.init(name: name)
    }
}

let rootFolder = Folder(name: "root", documents: [
    Folder(name: "folder1", documents: [
        Folder(name: "folder1.1", documents: []),
        Folder(name: "folder1.2", documents: []),
    ]),
    Folder(name: "folder2", documents: [
        Folder(name: "folder2.1", documents: []),
        Folder(name: "folder2.2", documents: []),
    ])
])

xxxApp.swift 文件中的ContentView() 对象需要.environmentObject(RootSelection())

import SwiftUI

@main
struct DraftApp: App {
    var body: some Scene {
        WindowGroup {
            ContentView()
                .environmentObject(RootSelection())
        }
    }
}

Answer 20

初级。 在根视图（您想要返回的位置）中使用 NavigationLink 和 isActive 设计器就足够了。在最后一个视图中，切换到控制 isActive 参数的 FALSE 变量。

在 Swift 5.5 版中，使用 .isDetaillink(false) 是可选的。

您可以使用我在示例中使用的一些通用类，或者通过绑定将此变量传递到 VIEW 层次结构中。使用对您来说更方便的方式。

class ViewModel: ObservableObject {
    @Published var isActivate = false
}

@main
struct TestPopToRootApp: App {
    let vm = ViewModel()
    
    var body: some Scene {
        WindowGroup {
            ContentView()
                .environmentObject(vm)
        }
    }
}

struct ContentView: View {
    @EnvironmentObject var vm: ViewModel
    
    var body: some View {
        NavigationView {
            NavigationLink("Go to view2", destination: NavView2(), isActive: $vm.isActivate)
            .navigationTitle(Text("Root view"))
        }
    }
}

struct NavView2: View {
    var body: some View {
        NavigationLink("Go to view3", destination: NavView3())
        .navigationTitle(Text("view2"))
    }
}

struct NavView3: View {
    @EnvironmentObject var vm: ViewModel
    
    var body: some View {
        Button {
            vm.isActivate = false
        } label: {
            Text("Back to root")
        }

        .navigationTitle(Text("view3"))
    }
}

Answer 21

更容易呈现和关闭包含 NavigationView 的模态视图控制器。将模态视图控制器设置为全屏并稍后将其关闭会产生与弹出到根目录的导航视图堆栈相同的效果。

https://www.hackingwithswift.com/quick-start/swiftui/how-to-present-a-full-screen-modal-view-using-fullscreencover