iOS:如何将视图从登录切换到主Content SwiftUi

import SwiftUI

struct LoginView: View {
    @State private var username: String = ""
    @State private var password: String = ""
    @State private var isLoggedIn: Bool = false
    
    var body: some View {
        VStack {
            TextField("Username", text: $username)
                .textFieldStyle(RoundedBorderTextFieldStyle())
                .padding()
            
            SecureField("Password", text: $password)
                .textFieldStyle(RoundedBorderTextFieldStyle())
                .padding()
            
            Button(action: {
                // Perform login validation here
                isLoggedIn = true
            }) {
                Text("Login")
                    .padding()
                    .background(Color.blue)
                    .foregroundColor(.white)
                    .cornerRadius(10)
            }
        }
        .padding()
    }
}

struct ContentView: View {
    var body: some View {
        Text("Main Content")
            .font(.largeTitle)
    }
}

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