在 SwiftUI 中单击按钮时的 NavigationView 和 NavigationLink？

Question

我正在尝试从登录视图推送到详细视图，但无法成功。即使导航栏未显示在登录视图中。如何在 SwiftUI 中按下按钮？如何在按钮点击时使用 NavigationLink？

var body: some View {
    
    NavigationView {
        VStack(alignment: .leading) {
            Text("Let's get you signed in.")
                .bold()
                .font(.system(size: 40))
                .multilineTextAlignment(.leading)
                .frame(width: 300, height: 100, alignment: .topLeading)
                .padding(Edge.Set.bottom, 50)
            
            Text("Email address:")
                .font(.headline)
            TextField("Email", text: $email)
                .frame(height:44)
                .accentColor(Color.white)
                .background(Color(UIColor.darkGray))
                .cornerRadius(4.0)
            
            Text("Password:")
                .font(.headline)
            
            SecureField("Password", text: $password)
                .frame(height:44)
                .accentColor(Color.white)
                .background(Color(UIColor.darkGray))
                .cornerRadius(4.0)
            
            Button(action: {
                print("login tapped")
            }) {
                HStack {
                    Spacer()
                    Text("Login").foregroundColor(Color.white).bold()
                    Spacer()
                }
            }
            .accentColor(Color.black)
            .padding()
            .background(Color(UIColor.darkGray))
            .cornerRadius(4.0)
            .padding(Edge.Set.vertical, 20)
        }
        .padding(.horizontal,30)
    }
    .navigationBarTitle(Text("Login"))
}

Answer 1

要解决您的问题，您需要使用NavigationLink 绑定和管理标签，因此在您的视图中创建一个状态如下，只需添加上面的正文。

@State var selection: Int? = nil

然后更新您的按钮代码如下添加NavigationLink

NavigationLink(destination: Text("Test"), tag: 1, selection: $selection) {
    Button(action: {
        print("login tapped")
        self.selection = 1
    }) {
        HStack {
            Spacer()
            Text("Login").foregroundColor(Color.white).bold()
            Spacer()
        }
    }
    .accentColor(Color.black)
    .padding()
    .background(Color(UIColor.darkGray))
    .cornerRadius(4.0)
    .padding(Edge.Set.vertical, 20)
}

Meaning is, when selection and NavigationLink tag value will match then navigation will be occurs.

希望对你有帮助。

Answer 2

接受的答案使用NavigationLink(destination:tag:selection:)，这是正确的。

但是，对于只有一个 NavigationLink 的简单视图，您可以使用 更简单 变体：NavigationLink(destination:isActive:)

---

用法#1

NavigationLink 由标准Button 激活：

struct ContentView: View {
    @State var isLinkActive = false

    var body: some View {
        NavigationView {
            VStack(alignment: .leading) {
                ...
                NavigationLink(destination: Text("OtherView"), isActive: $isLinkActive) {
                    Button(action: {
                        self.isLinkActive = true
                    }) {
                        Text("Login")
                    }
                }
            }
            .navigationBarTitle(Text("Login"))
        }
    }
}

---

用法#2

NavigationLink 被隐藏并由标准Button 激活：

struct ContentView: View {
    @State var isLinkActive = false

    var body: some View {
        NavigationView {
            VStack(alignment: .leading) {
                ...
                Button(action: {
                    self.isLinkActive = true
                }) {
                    Text("Login")
                }
            }
            .navigationBarTitle(Text("Login"))
            .background(
                NavigationLink(destination: Text("OtherView"), isActive: $isLinkActive) {
                    EmptyView()
                }
                .hidden()
            )
        }
    }
}

---

用法#3

NavigationLink 被隐藏并以编程方式激活：

struct ContentView: View {
    @State var isLinkActive = false

    var body: some View {
        NavigationView {
            VStack(alignment: .leading) {
                ...
            }
            .navigationBarTitle(Text("Login"))
            .background(
                NavigationLink(destination: Text("OtherView"), isActive: $isLinkActive) {
                    EmptyView()
                }
                .hidden()
            )
        }
        .onAppear {
            self.isLinkActive = true
        }
    }
}

---

_{这是一个GitHub repository，它带有不同的 SwiftUI 扩展，使导航更容易。}

Answer 3

另一种方法：

场景代理

if let windowScene = scene as? UIWindowScene {
            let window = UIWindow(windowScene: windowScene)
            window.rootViewController = UIHostingController(rootView: BaseView().environmentObject(ViewRouter()))
            self.window = window
            window.makeKeyAndVisible()
        }

基础视图

import SwiftUI

struct BaseView : View {

    @EnvironmentObject var viewRouter: ViewRouter

    var body: some View {
        VStack {
            if viewRouter.currentPage == "view1" {
                FirstView()
            } else if viewRouter.currentPage == "view2" {
                SecondView()
                    .transition(.scale)
            }
        }
    }
}

#if DEBUG
struct MotherView_Previews : PreviewProvider {
    static var previews: some View {
        BaseView().environmentObject(ViewRouter())
    }
}
#endif

ViewRouter

import Foundation
import Combine
import SwiftUI

class ViewRouter: ObservableObject {

    let objectWillChange = PassthroughSubject<ViewRouter,Never>()

    var currentPage: String = "view1" {
        didSet {
            withAnimation() {
                objectWillChange.send(self)
            }
        }
    }
}

第一视图

import SwiftUI

struct FirstView : View {

    @EnvironmentObject var viewRouter: ViewRouter

    var body: some View {
        VStack {
            Button(action: {self.viewRouter.currentPage = "view2"}) {
                NextButtonContent()
            }
        }
    }
}

#if DEBUG
struct FirstView_Previews : PreviewProvider {
    static var previews: some View {
        FirstView().environmentObject(ViewRouter())
    }
}
#endif

struct NextButtonContent : View {
    var body: some View {
        return Text("Next")
            .foregroundColor(.white)
            .frame(width: 200, height: 50)
            .background(Color.blue)
            .cornerRadius(15)
            .padding(.top, 50)
    }
}

第二视图

import SwiftUI

struct SecondView : View {

    @EnvironmentObject var viewRouter: ViewRouter

    var body: some View {
        VStack {
            Spacer(minLength: 50.0)
            Button(action: {self.viewRouter.currentPage = "view1"}) {
                BackButtonContent()
            }
        }
    }
}

#if DEBUG
struct SecondView_Previews : PreviewProvider {
    static var previews: some View {
        SecondView().environmentObject(ViewRouter())
    }
}
#endif

struct BackButtonContent : View {
    var body: some View {
        return Text("Back")
            .foregroundColor(.white)
            .frame(width: 200, height: 50)
            .background(Color.blue)
            .cornerRadius(15)
            .padding(.top, 50)
    }
}

希望这会有所帮助！