使用onAuthStateChanged使用Flutter登录Firebase [英] Firebase Login with Flutter using onAuthStateChanged

问题描述

在Flutter之外，当我实现Firebase身份验证时，我总是使用firebase提供的onAuthStateChanged侦听器来确定用户是否登录并做出相应的响应。

Outside of Flutter, when I implement firebase authentication I always use the onAuthStateChanged listener provided by firebase to determine if the user is logged in or not and respond accordingly.

我正在尝试使用flutter做类似的事情，但是我可以找到一种访问Firebase的onAuthStateChanged的方法。我正在使用firebase_auth和google_signin Flutter插件。我正在研究firebase_auth Flutter插件随附的示例代码。下面是示例代码。我可以使用google登录成功登录，但是示例太简单了，因为我想让观察者/侦听器检测用户的登录/退出状态。

I am trying to do something similar using flutter, but I can find a way to access onAuthStateChanged of Firebase. I am using the firebase_auth, and google_signin Flutter plugins. I am working of example code that is included with the firebase_auth Flutter plugin. Below is the sample code. I can login successfully with google sign in, but the example is too simple, because I want to have an observer/listener to detect the user's signed in/out state.

有没有一种方法可以使用firebase_auth / google_signin flutter插件通过观察者/侦听器进行检测，以确定用户的状态？

Is there a way to detect via observer/listener using the firebase_auth/google_signin flutter plugins to determine the status of a user?

我最终希望应用程序确定用户是否登录（是/否）。如果没有，则显示登录屏幕，如果是，则显示我的主应用程序页面。

Ultimately I want the app to determine if the user is logged in (yes/no). If not then show a login screen, if yes then show my main app page.

import 'dart:async';
import 'dart:io';

import 'package:flutter/material.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:google_sign_in/google_sign_in.dart';

final FirebaseAuth _auth = FirebaseAuth.instance;
final GoogleSignIn _googleSignIn = new GoogleSignIn();

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Firebase Auth Demo',
      home: new MyHomePage(title: 'Firebase Auth Demo'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => new _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  Future<String> _message = new Future<String>.value('');

  Future<String> _testSignInAnonymously() async {
    final FirebaseUser user = await _auth.signInAnonymously();
    assert(user != null);
    assert(user == _auth.currentUser);
    assert(user.isAnonymous);
    assert(!user.isEmailVerified);
    assert(await user.getToken() != null);
    if (Platform.isIOS) {
      // Anonymous auth doesn't show up as a provider on iOS
      assert(user.providerData.isEmpty);
    } else if (Platform.isAndroid) {
      // Anonymous auth does show up as a provider on Android
      assert(user.providerData.length == 1);
      assert(user.providerData[0].providerId == 'firebase');
      assert(user.providerData[0].uid != null);
      assert(user.providerData[0].displayName == null);
      assert(user.providerData[0].photoUrl == null);
      assert(user.providerData[0].email == null);
    }
    return 'signInAnonymously succeeded: $user';
  }

  Future<String> _testSignInWithGoogle() async {
    final GoogleSignInAccount googleUser = await _googleSignIn.signIn();
    final GoogleSignInAuthentication googleAuth =
        await googleUser.authentication;
    final FirebaseUser user = await _auth.signInWithGoogle(
      accessToken: googleAuth.accessToken,
      idToken: googleAuth.idToken,
    );
    assert(user.email != null);
    assert(user.displayName != null);
    assert(!user.isAnonymous);
    assert(await user.getToken() != null);
    return 'signInWithGoogle succeeded: $user';
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text(widget.title),
      ),
      body: new Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: <Widget>[
          new MaterialButton(
              child: const Text('Test signInAnonymously'),
              onPressed: () {
                setState(() {
                  _message = _testSignInAnonymously();
                });
              }),
          new MaterialButton(
              child: const Text('Test signInWithGoogle'),
              onPressed: () {
                setState(() {
                  _message = _testSignInWithGoogle();
                });
              }),
          new FutureBuilder<String>(
              future: _message,
              builder: (_, AsyncSnapshot<String> snapshot) {
                return new Text(snapshot.data ?? '',
                    style: const TextStyle(
                        color: const Color.fromARGB(255, 0, 155, 0)));
              }),
        ],
      ),
    );
  }
}

以下是有关有问题的软件包的链接：
https://github.com/flutter/plugins/tree/master/ packages / firebase_auth
https://github.com/ flutter / plugins / tree / master / packages / google_sign_in

Here are links to the flutter packages in question: https://github.com/flutter/plugins/tree/master/packages/firebase_auth https://github.com/flutter/plugins/tree/master/packages/google_sign_in

推荐答案

我知道这个问题已经很老了，但是这里

I know this question is pretty old, but here is the answer if anybody is still looking for it.

Firebase返回流的是答案FirebaseUser 及其 onAuthStateChanged 函数。有很多方法可以监听用户的身份验证状态更改。这是我的方法：

Firebase returns a Stream of FirebaseUser with it's onAuthStateChanged function. There are many ways to listen to the user's authentication state change. This is how I do it:

我返回了 StreamBuilder 到我的应用程序的主页，然后 StreamBuilder 根据用户的身份验证状态返回特定页面。

I return a StreamBuilder to my App's home page, and the StreamBuilder returns specific pages based on the auth status of the user.

@override
Widget build(BuildContext context) {
  return MaterialApp(
      title: 'Your App Name',
      home: _getLandingPage()
  );
}

Widget _getLandingPage() {
  return StreamBuilder<FirebaseUser>(
    stream: FirebaseAuth.instance.onAuthStateChanged,
    builder: (BuildContext context, snapshot) {
      if (snapshot.hasData) {
        if (snapshot.data.providerData.length == 1) { // logged in using email and password
          return snapshot.data.isEmailVerified
              ? MainPage()
              : VerifyEmailPage(user: snapshot.data);
        } else { // logged in using other providers
          return MainPage();
        }
      } else {
        return LoginPage();
      }
    },
  );
}

解决方案2

您也可以在应用程序的 initState（）函数中创建一个侦听器。

Solution 2

You can create a listener in your app's initState() function as well.

@override
void initState() {
  super.initState();

  FirebaseAuth.instance.onAuthStateChanged.listen((firebaseUser) {
    // do whatever you want based on the firebaseUser state
  });
}

这篇关于使用onAuthStateChanged使用Flutter登录Firebase的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！