SwiftUI 无法创建导航视图

Question

I'm following through some swiftUI tutorial and I couldn't figure out what this meant.

This was the very first step, and I haven't done anything other than adding the NavigationView. How do I resolve this?

Answer 1

That's just container, you need some content inside, If you are just trying something out try following:

var body: some View {
    NavigationView {
        Text("Testing")
    }
}

Answer 2

You cannot have an empty NavigationView . Add something inside.

struct ContentView: View {
    var body: some View {
        NavigationView {
            Text("Text here")
        }
    }
}

Answer 3

FIRST: Add new SwiftUI-View (Name: MapView.swift without code-changing ) SECOND: Add new SwiftUI-View (Name: SecondView.swift) THEN Change ContentView and SecondView:

a) ContentView.swift

import SwiftUI

struct ContentView: View {
    var body: some View {
        VStack {
            MapView() // on upper Screen will appear: "Hello World"
            NavigationView {
                NavigationLink(destination: SecondView()) {
                    VStack {
                        Text("click here")
                            .fontWeight(.heavy)
                            .font(.largeTitle)
                            .padding()
                        Text("go to screen II")
                    }
                }
            } //End of NavigationView
            
        }// End of VStack
    }
}


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

b) SecondView.swift

import SwiftUI

struct SecondView: View {
    var body: some View {
        VStack {
            Text("Screen II")
                .fontWeight(.heavy)
                .foregroundColor(.blue)
                .font(.largeTitle)
                .padding()
            Text("you changed it")
            Text("GRATULATION!")
        }
    }
}

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

c) MapView.swift

import SwiftUI

struct MapView: View {
    var body: some View {
        Text(/*@START_MENU_TOKEN@*/"Hello, World!"/*@END_MENU_TOKEN@*/)
    }
}

struct MapView_Previews: PreviewProvider {
    static var previews: some View {
        MapView()
    }
}