开发者问题收集

Flutter Web 和 Firebase 身份验证 TypeError：无法读取未定义的属性“app”

2020-05-10
13903
firebase flutter google-cloud-firestore

有人能帮帮我吗？我尝试使用 Flutter 构建一个基于 Google Firebase Auth 和 Cloud Firestore 的 Web 应用程序。Android 上的项目运行良好，我可以与用户合作并从我的 Cloud Firestore 数据库中获取数据。 我已经制作了第二个应用程序 (webapp)，执行了 Firebase 文档中描述的所有步骤（webapp 已注册，托管在 Firebase 上），在 pubspec.yaml 中插入了所有依赖项 

dependencies:
  flutter:
    sdk: flutter

  # The following adds the Cupertino Icons font to your application.
  # Use with the CupertinoIcons class for iOS style icons.
  cupertino_icons: ^0.1.3
  firebase_core: ^0.4.4+3
  firebase: ^7.3.0
  firebase_auth: ^0.16.0

像这样修改了 index.html： 

<body>
  <!-- The core Firebase JS SDK is always required and must be listed first -->
  <script src="/__/firebase/7.14.3/firebase-app.js"></script>

  <!-- TODO: Add SDKs for Firebase products that you want to use
     https://firebase.google.com/docs/web/setup#available-libraries -->
  <script src="/__/firebase/7.14.3/firebase-analytics.js"></script>
  <!-- Add Firebase products that you want to use -->
  <script src="https://www.gstatic.com/firebasejs/7.14.2/firebase-auth.js"></script>
  <script src="https://www.gstatic.com/firebasejs/7.14.2/firebase-firestore.js"></script>
  <!-- Initialize Firebase -->
  <script src="/__/firebase/init.js"></script>  <!-- This script installs service_worker.js to provide PWA functionality to
       application. For more information, see:
       https://developers.google.com/web/fundamentals/primers/service-workers -->
  <script>
    if ('serviceWorker' in navigator) {
      window.addEventListener('load', function () {
        navigator.serviceWorker.register('flutter_service_worker.js');
      });
    }
  </script>
  <script>
    var firebaseConfig = {
      apiKey: "XXXXXXXXXX-6EL5qIBxWjurRQMcK3pf9W-o",
      authDomain: "xxxxxxxx.firebaseapp.com",
      databaseURL: "https://xxxxxxxx.firebaseio.com",
      projectId: "xxxxxxxx",
      storageBucket: "xxxxxxxx.appspot.com",
      messagingSenderId: "xxxxxxxx6198",
      appId: "1:xxxxxxxx16198:web:cde3457e8dc734d045d227",
      measurementId: "X-XXXXXXXXXX"
    };
    firebase.initializeApp(firebaseConfig);
    firebase.auth();
    firebase.analytics();
  </script>
  <script src="main.dart.js" type="application/javascript"></script>
</body>

但是当我尝试登录或注册时，Android Studio 抛出了此错误消息： 

TypeError: Cannot read property 'app' of undefined
    at Object.app$ [as app] (http://localhost:53262/packages/firebase/src/top_level.dart.lib.js:72:56)
    at firebase_auth_web.FirebaseAuthWeb.new.[_getAuth] (http://localhost:53262/packages/firebase_auth_web/firebase_auth_web.dart.lib.js:42:27)
    at firebase_auth_web.FirebaseAuthWeb.new.signInWithCredential (http://localhost:53262/packages/firebase_auth_web/firebase_auth_web.dart.lib.js:197:34)
    at signInWithCredential.next (<anonymous>)
    at runBody (http://localhost:53262/dart_sdk.js:43135:34)
    at Object._async [as async] (http://localhost:53262/dart_sdk.js:43163:7)
    at firebase_auth_web.FirebaseAuthWeb.new.signInWithCredential (http://localhost:53262/packages/firebase_auth_web/firebase_auth_web.dart.lib.js:196:20)
    at firebase_auth.FirebaseAuth.__.signInWithCredential (http://localhost:53262/packages/firebase_auth/firebase_auth.dart.lib.js:324:90)
    at signInWithCredential.next (<anonymous>)

这个异常是什么意思？我做错了什么？ 非常感谢您的帮助！

3个回答

我遇到了同样的问题，浪费了很多时间。 至少对我来说，这个问题的主要原因是 cloud_firestore 依赖项。对我来说，结果发现这只是一些与 firebase 安全有关的问题，因为我使用 VPN 访问互联网，而通常弹出的 chrome 调试浏览器不允许安装扩展。 对我来说，一切都很好，但我只是被阻止访问一些 firebase 内容。要尝试是否是这种情况，请运行 flutter run -d chrome --release 并复制本地主机 url 并将其粘贴到普通浏览器中，而不是弹出窗口中。如果一切正常，那么您遇到了与我相同的问题，如果不是，那么也许您遇到了不同的问题。 希望这可以节省某人的时间。

请记住，您的 index.html 文件应正确配置，还应包括 pubspec.yaml 上的每个 firebase 依赖项。 下面是一个配置良好的 index.html 示例，仅包含 body 标签： 

<body id="app-container">

 // firebase-app.js should go first.
 <script src="https://www.gstatic.com/firebasejs/7.20.0/firebase-app.js"></script>
 <script src="https://www.gstatic.com/firebasejs/7.20.0/firebase-analytics.js"></script>
 <script src="https://www.gstatic.com/firebasejs/7.20.0/firebase-auth.js"></script>
 <script src="https://www.gstatic.com/firebasejs/7.20.0/firebase-firestore.js">. </script>

        <script>
          // Your web app's Firebase configuration
          // For Firebase JS SDK v7.20.0 and later, measurementId is optional
          var firebaseConfig = {
            apiKey: "xxxxxxxxxxxxx",
            authDomain: "xxxxxx.firebaseapp.com",
            databaseURL: "https://xxxxxx.firebaseio.com",
            projectId: "xxxxx",
            storageBucket: "xxxxx.appspot.com",
            messagingSenderId: "xxxxxxx",
            appId: "1:xxxxxxxxx:web:xxxxxxxxxx",
            measurementId: "G-NYEW95QM"
          };
          // Initialize Firebase
          firebase.initializeApp(firebaseConfig);
          firebase.analytics();

        </script>

    <script src="main.dart.js" type="application/javascript"></script>


</body>

我的 pubspec.yaml 文件如下所示： 

cupertino_icons: ^1.0.0
  firebase_auth: ^0.18.2
  cloud_firestore: ^0.14.2
  provider: ^4.3.2+2
  flutter_spinkit: ^4.1.2+1
  simple_animations: ^2.2.3
  firebase_core: ^0.5.1
  intl: ^0.16.1
  folding_cell: ^1.0.0
  charts_flutter: ^0.9.0
  flip_card: ^0.4.4
  progress_dialog: ^1.2.4
  image_picker_web: ^0.1.0+2
  url_launcher: ^5.7.8

  image: ^2.1.18
  animator: ^2.0.1
  timeago: ^2.0.28
  uuid: ^2.2.2

  font_awesome_flutter: ^8.10.0
  bubble: ^1.1.9+1
  google_fonts: ^1.1.1
Frank Tz
2020-10-31

您需要修复依赖项。 

dependencies:
  flutter:
    sdk: flutter
  firebase_auth:
  firebase_auth_web:
Павел Ковалев
2020-05-24

尝试运行 flutter doctor，查看摘要中是否有“Chrome - 为 Web 开发” 

[√] Flutter (Channel beta, 1.24.0-10.2.pre, on Microsoft Windows [Version 10.0.18363.1198], locale en-US)
[√] Android toolchain - develop for Android devices (Android SDK version 29.0.3)
[√] Chrome - develop for the web  <- THIS
[√] Android Studio (version 4.0)
[√] Connected device (3 available)

如果没有，请尝试按照 此 答案中的步骤切换到 flutter beta 频道并创建正确的文件。

您可能必须为您的应用启用 Web 支持，如 此处 所示

William Humphries
2020-12-01