SwiftUI中Google登录导航异常：取消登录返回根视图

问题根源 #

你遇到的取消登录后跳回根视图的问题，通常是因为未正确指定Google登录弹窗的presentingViewController，或者使用了不兼容SwiftUI的旧版登录API，导致登录流程结束后导航栈被意外重置。

方案1：使用Google Sign-In 7.0+的SwiftUI原生异步API #

Google Sign-In iOS SDK 7.0及以上提供了适配SwiftUI的异步方法signInWithPresenting，无需手动获取ViewController，能自动适配当前视图上下文，取消登录后不会跳转回根视图。

步骤： #

1. 确保你的GoogleSignIn Pod版本≥7.0
2. 在ViewModel中实现异步登录方法：

class AuthViewModel: ObservableObject {
    func signInWithGoogle() async {
        do {
            // 自动适配当前SwiftUI视图上下文
            let signInResult = try await GIDSignIn.sharedInstance.signInWithPresenting(presenting: nil)
            let googleUser = signInResult.user
            
            // 提取Google凭证并传给Firebase
            guard let idToken = googleUser.idToken?.tokenString else { return }
            let accessToken = googleUser.accessToken.tokenString
            let firebaseCredential = GoogleAuthProvider.credential(withIDToken: idToken, accessToken: accessToken)
            
            // Firebase验证登录
            let authResult = try await Auth.auth().signIn(with: firebaseCredential)
            // 处理登录成功逻辑（比如导航到首页）
        } catch {
            // 登录取消或失败时，停留在当前页面
            print("登录操作终止：\(error.localizedDescription)")
        }
    }
}

3. 在注册第三页的SwiftUI视图中调用该方法：

struct SignUpThirdPage: View {
    @EnvironmentObject var authVM: AuthViewModel
    
    var body: some View {
        Button("通过Google完成注册") {
            Task {
                await authVM.signInWithGoogle()
            }
        }
    }
}

方案2：手动获取当前ViewController作为弹窗宿主 #

如果无法升级SDK版本，可以通过环境变量注入当前ViewController，确保Google登录弹窗从当前注册页面的VC弹出，取消后不会影响导航栈。

步骤： #

1. 创建获取ViewController的工具代码：

// 用于获取当前ViewController的ViewModifier
struct ViewControllerInjector: UIViewControllerRepresentable {
    @Binding var viewController: UIViewController?
    
    func makeUIViewController(context: Context) -> UIViewController {
        UIViewController()
    }
    
    func updateUIViewController(_ uiViewController: UIViewController, context: Context) {
        DispatchQueue.main.async {
            viewController = uiViewController.parent
        }
    }
}

// 扩展环境变量，方便在SwiftUI视图中获取VC
extension EnvironmentValues {
    private struct CurrentVCKey: EnvironmentKey {
        static var defaultValue: UIViewController? = nil
    }
    
    var currentViewController: UIViewController? {
        get { self[CurrentVCKey.self] }
        set { self[CurrentVCKey.self] = newValue }
    }
}

extension View {
    func injectCurrentViewController() -> some View {
        let vcBinding = Binding<UIViewController?>(
            get: { self.environment(\.currentViewController).wrappedValue },
            set: { self.environment(\.currentViewController, $0) }
        )
        return self.background(ViewControllerInjector(viewController: vcBinding))
    }
}

2. 在注册流程的根导航视图中注入VC：

struct SignUpNavigationStack: View {
    var body: some View {
        NavigationStack {
            SignUpFirstPage()
                .navigationDestination(for: SignUpStep.self) { step in
                    switch step {
                    case .second: SignUpSecondPage()
                    case .third: SignUpThirdPage()
                    }
                }
        }
        .injectCurrentViewController()
    }
}

3. 在第三页视图中调用登录时指定presentingVC：

struct SignUpThirdPage: View {
    @Environment(\.currentViewController) var currentVC
    @EnvironmentObject var authVM: AuthViewModel
    
    var body: some View {
        Button("通过Google完成注册") {
            authVM.signInWithGoogle(presentingVC: currentVC)
        }
    }
}

4. ViewModel中的登录方法：

class AuthViewModel: ObservableObject {
    func signInWithGoogle(presentingVC: UIViewController?) {
        guard let vc = presentingVC else { return }
        let config = GIDConfiguration(clientID: FirebaseApp.app()?.options.clientID ?? "")
        
        GIDSignIn.sharedInstance.signIn(with: config, presenting: vc) { user, error in
            if let error = error {
                // 取消登录时停留在当前页面
                print("登录操作终止：\(error.localizedDescription)")
                return
            }
            
            guard let auth = user?.authentication else { return }
            let credential = GoogleAuthProvider.credential(withIDToken: auth.idToken!, accessToken: auth.accessToken!)
            
            Auth.auth().signIn(with: credential) { result, error in
                // 处理Firebase登录结果
            }
        }
    }
}

关键注意事项 #

• 方案1是官方推荐的SwiftUI适配方案，代码更简洁且不易出错
• 确保Info.plist中的Google登录配置（URL Scheme等）正确，避免其他跳转异常
• 测试时要覆盖取消登录的场景，确认导航栈未被重置

内容的提问来源于stack exchange，提问作者Swiss