flutter firebase 谷歌注销不工作

Question

我正在尝试实施谷歌登录/注销，但我的注销不起作用。 我收到一个错误 signOut() was called on null。当我在用户登录后打印出用户时，我确实获得了所有正确的信息，但是当我在我的注销 function 中打印出时，它说它是 null。自定义 firebase 用户确实工作。 这是我的 auth.dart 文件：

import 'dart:async';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:google_sign_in/google_sign_in.dart';

abstract class BaseAuth {
  Future<String> signIn(String email, String password);

  Future<String> signUp(String email, String password);

  Future<FirebaseUser> getCurrentUser();

  Future<void> sendEmailVerification();

  Future<void> signOut();

  Future<bool> isEmailVerified();

  Future<String> signInWithGoogle();
}

class Auth implements BaseAuth {
  final FirebaseAuth _firebaseAuth = FirebaseAuth.instance;
  final GoogleSignIn googleSignIn = GoogleSignIn();
  FirebaseUser user;

  Future<String> signIn(String email, String password) async {

    user = (await _firebaseAuth.signInWithEmailAndPassword(email: email, password: password)).user;
    return user.email;
  }

  Future<String> signUp(String email, String password) async {
    FirebaseUser user = (await _firebaseAuth.createUserWithEmailAndPassword(
        email: email, password: password)).user;
    return user.uid;
  }

  Future<FirebaseUser> getCurrentUser() async {
    user = await _firebaseAuth.currentUser();
    return user;
  }
  signOut() async {
    //print("signed in user: ${authService.user}");
    await _firebaseAuth.signOut();
  }

  Future<void> sendEmailVerification() async {
    FirebaseUser user = await _firebaseAuth.currentUser();
    user.sendEmailVerification();
  }

  Future<bool> isEmailVerified() async {
    FirebaseUser user = await _firebaseAuth.currentUser();
    return user.isEmailVerified;
  }

  Future<String> signInWithGoogle() async {
    final GoogleSignInAccount googleSignInAccount = await googleSignIn.signIn();
    final GoogleSignInAuthentication googleSignInAuthentication =
    await googleSignInAccount.authentication;

    final AuthCredential credential = GoogleAuthProvider.getCredential(
      accessToken: googleSignInAuthentication.accessToken,
      idToken: googleSignInAuthentication.idToken,
    );

   user = (await _firebaseAuth.signInWithCredential(credential)).user;

    assert(!user.isAnonymous);
    assert(await user.getIdToken() != null);

    final FirebaseUser currentUser = await _firebaseAuth.currentUser();
    assert(user.uid == currentUser.uid);
    return 'signInWithGoogle succeeded: $user';
  }

}

还有一点奇怪的是，如果我启动应用程序并且已经登录（作为谷歌），我点击注销并且它似乎可以工作。 我的控制台中没有任何内容，但它会返回到登录屏幕。 然后，如果我以 google 身份重新登录并注销，就会开始发生错误。 另一件奇怪的事情是，如果我碰巧已经登录了，我点击一下就退出了，如果我在 android studio 中重新启动我的应用程序而不做任何更改，它会让我回到我应该已经登录的屏幕。这只发生在谷歌退出时（不是 firebase 退出）。 知道我可能做错了什么吗？ 谢谢

pubspec.yaml

dependencies:
  firebase_auth: ^0.14.0+5

  firebase_database: ^3.0.7
  google_sign_in: ^4.0.7
  firebase_storage:
  image_picker:
  cloud_firestore:
  shared_preferences:
  fluttertoast:
  cached_network_image:
  intl:

我使用它的一页：（我有很多，但实现方式与此类似，但在我的任何页面中都不起作用）

import 'package:flutter/material.dart';
import 'package:pet_helper/chat.dart';
import 'package:pet_helper/lost_and_found.dart';
import 'package:pet_helper/pet_adoption.dart';
import 'authentication.dart';

class HomePage extends StatefulWidget {
  HomePage({Key key, this.auth, this.userId, this.onSignedOut})
      : super(key: key);

  final BaseAuth auth;
  final VoidCallback onSignedOut;
  final String userId;

  @override
  State<StatefulWidget> createState() => new _HomePageState();
}

class _HomePageState extends State<HomePage> {

  final GlobalKey<FormState> formKey = GlobalKey<FormState>();
  int _currentIndex = 0;

  @override
  void initState() {
    super.initState();
  }
  final List<Widget> _children = [
    new LostAndFoundPage(),
    new PetAdoptionPage(),
    new ChatPage(),
  ];
  _signOut() async {
    try {
      await widget.auth.signOut();
      widget.onSignedOut();
    } catch (e) {

      print(e);
    }
  }

  onTabTapped(int index) {
    setState(() {
      _currentIndex = index;
    });
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
        appBar: new AppBar(
          automaticallyImplyLeading:false,
          title: new Text('Pet Helper'),
          actions: <Widget>[
            new FlatButton(
                child: new Text('Logout',
                    style: new TextStyle(fontSize: 17.0, color: Colors.white)),
                onPressed: _signOut)
          ],
        ),
        body: _children[_currentIndex], // new
        bottomNavigationBar: BottomNavigationBar(
          onTap: onTabTapped, // new
          currentIndex: _currentIndex, // new
          items: [
            new BottomNavigationBarItem(
              icon: Icon(Icons.home),
              title: Text('Lost & Found'),
            ),
            new BottomNavigationBarItem(
              icon: Icon(Icons.pets),
              title: Text('Pet Adoption'),
            ),
            new BottomNavigationBarItem(
                icon: Icon(Icons.person), title: Text('Chat'))
          ],
        ));
  }
}

为了完成，这是我的登录页面：

import 'package:flutter/material.dart';
import 'package:pet_helper/home_page.dart';
import 'authentication.dart';

class LoginSignUpPage extends StatefulWidget {
  LoginSignUpPage({this.auth, this.onSignedIn});

  final BaseAuth auth;
  final VoidCallback onSignedIn;

  @override
  State<StatefulWidget> createState() => new _LoginSignUpPageState();
}

enum FormMode { LOGIN, SIGNUP }
class _LoginSignUpPageState extends State<LoginSignUpPage> {
  final _formKey = new GlobalKey<FormState>();
  String _email;
  String _password;
  String _errorMessage;

  // Initial form is login form
  FormMode _formMode = FormMode.LOGIN;
  bool _isIos;
  bool _isLoading;

  // Check if form is valid before perform login or signup
  bool _validateAndSave() {
    final form = _formKey.currentState;
    if (form.validate()) {
      form.save();
      return true;
    }
    return false;
  }

  // Perform login or signup
  void _validateAndSubmit() async {
    setState(() {
      _errorMessage = "";
      _isLoading = true;
    });
    if (_validateAndSave()) {
      String userId = "";
      try {
        if (_formMode == FormMode.LOGIN) {
          userId = await widget.auth.signIn(_email, _password);
          print('Signed in: $userId');
        } else {
          userId = await widget.auth.signUp(_email, _password);
          widget.auth.sendEmailVerification();
          _showVerifyEmailSentDialog();
          print('Signed up user: $userId');
        }
        setState(() {
          _isLoading = false;
        });

        if (userId.length > 0 && userId != null && _formMode == FormMode.LOGIN) {
          widget.onSignedIn();
        }

      } catch (e) {
        print('Error: $e');
        setState(() {
          _isLoading = false;
          if (_isIos) {
            _errorMessage = e.details;
          } else
            _errorMessage = 'Incorrect user or password';
        });
      }
    }
  }


  @override
  void initState() {
    _errorMessage = "";
    _isLoading = false;
    super.initState();
  }

  void _changeFormToSignUp() {
    _formKey.currentState.reset();
    _errorMessage = "";
    setState(() {
      _formMode = FormMode.SIGNUP;
    });
  }

  void _changeFormToLogin() {
    _formKey.currentState.reset();
    _errorMessage = "";
    setState(() {
      _formMode = FormMode.LOGIN;
    });
  }

  @override
  Widget build(BuildContext context) {
    _isIos = Theme.of(context).platform == TargetPlatform.iOS;
    return new Scaffold(
        appBar: new AppBar(
          title: new Text('Pet Helper'),
        ),
        body: Stack(
          children: <Widget>[
            _showBody(),
            _showCircularProgress(),
          ],
        ));
  }

  Widget _showCircularProgress(){
    if (_isLoading) {
      return Center(child: CircularProgressIndicator());
    } return Container(height: 0.0, width: 0.0,);

  }

  void _showVerifyEmailSentDialog() {
    showDialog(
      context: context,
      builder: (BuildContext context) {
        // return object of type Dialog
        return AlertDialog(
          title: new Text("Verify your account"),
          content: new Text("Link to verify account has been sent to your email"),
          actions: <Widget>[
            new FlatButton(
              child: new Text("Dismiss"),
              onPressed: () {
                _changeFormToLogin();
                Navigator.of(context).pop();
              },
            ),
          ],
        );
      },
    );
  }

  Widget _showBody(){
    return new Container(
        padding: EdgeInsets.all(16.0),
        child: new Form(
          key: _formKey,
          child: new ListView(
            shrinkWrap: true,
            children: <Widget>[
              _showLogo(),
              _showEmailInput(),
              _showPasswordInput(),
              _showErrorMessage(),
              _showPrimaryButton(),
              _showSecondaryButton(),
              _googleSignInButton(),

            ],
          ),
        ));
  }

  Widget _showErrorMessage() {
    if (_errorMessage.length > 0 && _errorMessage != null) {
      return new Text(
        _errorMessage,
        style: TextStyle(
            fontSize: 13.0,
            color: Colors.red,
            height: 1.0,
            fontWeight: FontWeight.w300),
      );
    } else {
      return new Container(
        height: 0.0,
      );
    }
  }

  Widget _showLogo() {
    return new Hero(
      tag: 'hero',
      child: Padding(
        padding: EdgeInsets.fromLTRB(0.0, 30.0, 0.0, 0.0),
        child: CircleAvatar(
          backgroundColor: Colors.transparent,
          radius: 120.0,
          child: Image.asset('assets/babies.png'),
        ),
      ),
    );
  }

  Widget _showEmailInput() {
    return Padding(
      padding: const EdgeInsets.fromLTRB(0.0, 25.0, 0.0, 0.0),
      child: new TextFormField(
        maxLines: 1,
        keyboardType: TextInputType.emailAddress,
        autofocus: false,
        decoration: new InputDecoration(
            hintText: 'Email',
            icon: new Icon(
              Icons.mail,
              color: Colors.grey,
            )),
        validator: (String value) {
        if (value.isEmpty) {
          _isLoading = false;
          return 'Email can\'t be empty';
        }
        else{
          return null;
        }
      },
        onSaved: (value) => _email = value.trim(),
      ),
    );
  }

  Widget _showPasswordInput() {
    return Padding(
      padding: const EdgeInsets.fromLTRB(0.0, 15.0, 0.0, 0.0),
      child: new TextFormField(
        maxLines: 1,
        obscureText: true,
        autofocus: false,
        decoration: new InputDecoration(
            hintText: 'Password',
            icon: new Icon(
              Icons.lock,
              color: Colors.grey,
            )),
        validator: (String value) {
          if (value.isEmpty) {
            _isLoading = false;
            return 'Password can\'t be empty';
          }
          else{
            return null;
          }
        },
        onSaved: (value) => _password = value.trim(),
      ),
    );
  }

  Widget _showSecondaryButton() {
    return new FlatButton(
      child: _formMode == FormMode.LOGIN
          ? new Text('Create an account',
          style: new TextStyle(fontSize: 18.0, fontWeight: FontWeight.w300))
          : new Text('Have an account? Sign in',
          style:
          new TextStyle(fontSize: 18.0, fontWeight: FontWeight.w300)),
      onPressed: _formMode == FormMode.LOGIN
          ? _changeFormToSignUp
          : _changeFormToLogin,
    );
  }

  Widget _showPrimaryButton() {
    return new Padding(
        padding: EdgeInsets.fromLTRB(0.0, 35.0, 0.0, 0.0),
        child: SizedBox(
          height: 40.0,
          child: new RaisedButton(
            elevation: 5.0,
            shape: new RoundedRectangleBorder(borderRadius: new BorderRadius.circular(30.0)),
            color: Colors.blue,
            child: _formMode == FormMode.LOGIN
                ? new Text('Login',
                style: new TextStyle(fontSize: 20.0, color: Colors.white))
                : new Text('Create account',
                style: new TextStyle(fontSize: 20.0, color: Colors.white)),
            onPressed: _validateAndSubmit,
          ),
        ));
  }

void submitGoogleLogin() async{
  setState(() {
    _errorMessage = "";
    _isLoading = true;
  });
  String userId = "";
  userId = await widget.auth.signInWithGoogle().whenComplete(() {
    widget.onSignedIn();
    Navigator.of(context).push(
      MaterialPageRoute(
        builder: (context) {
          return new HomePage();
        },
      ),
    );
  });
  print('Signed in: $userId');
}

  Widget _googleSignInButton() {
    return OutlineButton(
      splashColor: Colors.grey,
      onPressed: submitGoogleLogin,
      shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(40)),
      highlightElevation: 0,
      borderSide: BorderSide(color: Colors.grey),
      child: Padding(
        padding: const EdgeInsets.fromLTRB(0, 10, 0, 10),
        child: Row(
          mainAxisSize: MainAxisSize.min,
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Image(image: AssetImage("assets/google_logo.png"), height: 30.0),
            Padding(
              padding: const EdgeInsets.only(left: 10),
              child: Text(
                'Sign in with Google',
                style: TextStyle(
                  fontSize: 15,
                  color: Colors.grey,
                ),
              ),
            )
          ],
        ),
      ),
    );
  }
}

哦，根页面更改了用户的 state：

import 'package:flutter/material.dart';
import 'login_signup_page.dart';
import 'authentication.dart';
import 'home_page.dart';

class RootPage extends StatefulWidget {
  RootPage({this.auth});

  final BaseAuth auth;

  @override
  State<StatefulWidget> createState() => new _RootPageState();
}

enum AuthStatus {
  NOT_DETERMINED,
  NOT_LOGGED_IN,
  LOGGED_IN,
}

class _RootPageState extends State<RootPage> {
  AuthStatus authStatus = AuthStatus.NOT_DETERMINED;
  String _userId = "";

  @override
  void initState() {
    super.initState();
    widget.auth.getCurrentUser().then((user) {
      setState(() {
        if (user != null) {
          _userId = user?.uid;
        }
        authStatus =
        user?.uid == null ? AuthStatus.NOT_LOGGED_IN : AuthStatus.LOGGED_IN;
      });
    });
  }

  void _onLoggedIn() {
    widget.auth.getCurrentUser().then((user){
      setState(() {
        _userId = user.uid.toString();
      });
    });
    setState(() {
      authStatus = AuthStatus.LOGGED_IN;

    });
  }

  void _onSignedOut() {
    setState(() {
      authStatus = AuthStatus.NOT_LOGGED_IN;
      _userId = "";
    });
  }

  Widget _buildWaitingScreen() {
    return Scaffold(
      body: Container(
        alignment: Alignment.center,
        child: CircularProgressIndicator(),
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    switch (authStatus) {
      case AuthStatus.NOT_DETERMINED:
        return _buildWaitingScreen();
        break;
      case AuthStatus.NOT_LOGGED_IN:
        return new LoginSignUpPage(
          auth: widget.auth,
          onSignedIn: _onLoggedIn,
        );
        break;
      case AuthStatus.LOGGED_IN:
        if (_userId.length > 0 && _userId != null) {
          return new HomePage(
            userId: _userId,
            auth: widget.auth,
            onSignedOut: _onSignedOut,
          );
        } else return _buildWaitingScreen();
        break;
      default:
        return _buildWaitingScreen();
    }
  }
}

初始化根页面 Main.dart

void main() async{
  runApp(new MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
        title: 'Pet Helper',
        debugShowCheckedModeBanner: false,
        theme: new ThemeData(
          primarySwatch: Colors.blue,
        ),
        home: new RootPage(auth: new Auth()));
  }
}

Answer 1

abstract class BaseAuth {
  Future<String> signIn(String email, String password);

  Future<String> signUp(String email, String password);

  Future<FirebaseUser> getCurrentUser();

  Future<void> sendEmailVerification();

  Future<void> signOut();

  Future<bool> isEmailVerified();

  Future<String> signInWithGoogle();

  void signOutGoogle();
}

class Auth implements BaseAuth {
  final FirebaseAuth _firebaseAuth = FirebaseAuth.instance;
  final GoogleSignIn googleSignIn = GoogleSignIn();
  FirebaseUser user;

  Future<String> signIn(String email, String password) async {

    user = (await _firebaseAuth.signInWithEmailAndPassword(email: email, password: password)).user;
    return user.email;
  }

  Future<String> signUp(String email, String password) async {
    FirebaseUser user = (await _firebaseAuth.createUserWithEmailAndPassword(
        email: email, password: password)).user;
    return user.uid;
  }

  Future<FirebaseUser> getCurrentUser() async {
    user = await _firebaseAuth.currentUser();
    return user;
  }
  signOut() async {
    print("signed in user: $user");
    await _firebaseAuth.signOut();
  }

  Future<void> sendEmailVerification() async {
    FirebaseUser user = await _firebaseAuth.currentUser();
    user.sendEmailVerification();
  }

  Future<bool> isEmailVerified() async {
    FirebaseUser user = await _firebaseAuth.currentUser();
    return user.isEmailVerified;
  }

  Future<String> signInWithGoogle() async {
    final GoogleSignInAccount googleSignInAccount = await googleSignIn.signIn();
    final GoogleSignInAuthentication googleSignInAuthentication =
    await googleSignInAccount.authentication;

    final AuthCredential credential = GoogleAuthProvider.getCredential(
      accessToken: googleSignInAuthentication.accessToken,
      idToken: googleSignInAuthentication.idToken,
    );

   user = (await _firebaseAuth.signInWithCredential(credential)).user;

    assert(!user.isAnonymous);
    assert(await user.getIdToken() != null);

    final FirebaseUser currentUser = await _firebaseAuth.currentUser();
    assert(user.uid == currentUser.uid);
    return 'signInWithGoogle succeeded: $user';
  }
}

final Auth authService = Auth(); // add this to the bottom outside the class

使用全局变量

所以让我解释一下。 每次调用Auth() ，它都会创建该类的一个新实例。 因此，在一种情况下，您可能会登录用户。在另一种情况下，您可能会注销用户。 变量将包含变量的不同值。 因此，如果您使用与登录用户不同的实例来注销用户，则用户变量将为空，因此不允许您将其注销并打印空值。

解决方案

解决办法是一个全局变量访问一次Auth类。 前任。 var authService = Auth();

将变量放在 Auth 类之外，以便可以在任何类的任何地方访问它

Answer 2

谢谢大家的回答和支持。 我发现了问题。 登录 google 时，widget.onSignedIn 将我重定向到主页（在根页面中）。 我在调用 SignedIn 后重定向到谷歌登录按钮中的主页，这就是我失去用户变量范围的方式。 谢谢大家！

Answer 3

在我的例子中，每当我通过用 GetBuilder 包装的按钮调用注销 function 时，我都会收到错误：“null 值上使用的空检查运算符”。 所以解决方案是我必须先启动 controller，然后再调用它：

GetBuilder<LoginController>(
                init: LoginController(),// **I was missing this part**
                builder: (controller) {
                  return Column(...)});