Question

我正在制作一个应用程序并将其放到网络中。但是当我启动它时，在 chrome 中有一个空白屏幕。 chrome 中的控制台有我的日志：

Installed new service worker.
zone.dart:1339 Uncaught ReferenceError: firebase is not defined
at Object.ad5 (core.dart:54)
at Object.ajF (cloud_firestore_web.dart:36)
at cloud_firestore_web.dart:29
at ad0.a (async_patch.dart:316)
at ad0.$2 (async_patch.dart:341)
at Object.U (async_patch.dart:246)
at adP (main.dart:10)
at js_helper.dart:2684
at js_helper.dart:2684
at dartProgram (js_helper.dart:2684)

这是我的 main.dart 文件：

import 'package:brew_crew/screens/wrapper.dart';
import 'package:brew_crew/services/auth.dart';
import 'package:flutter/material.dart';
import 'package:firebase_core/firebase_core.dart';
import 'package:provider/provider.dart';
import 'package:brew_crew/models/user.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
  runApp(MyApp());
}

 class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return StreamProvider<UserClass>.value(
      value: AuthService().user,
      child: MaterialApp(
        home: Wrapper(),
      ),
    );
  }
}

还有一个 index.html 文件

    <!DOCTYPE html>
    <html>
    <head>
      <!--
        If you are serving your web app in a path other than the root, change the
        href value below to reflect the base path you are serving from.

        The path provided below has to start and end with a slash "/" in order for
        it to work correctly.

        For more details:
        * https://developer.mozilla.org/en-US/docs/Web/HTML/Element/base
      -->
      <base href="/">

      <meta charset="UTF-8">
      <meta content="IE=Edge" http-equiv="X-UA-Compatible">
      <meta name="description" content="A new Flutter project.">

      <!-- iOS meta tags & icons -->
      <meta name="apple-mobile-web-app-capable" content="yes">
      <meta name="apple-mobile-web-app-status-bar-style" content="black">
      <meta name="apple-mobile-web-app-title" content="brew_crew">
      <link rel="apple-touch-icon" href="icons/Icon-192.png">

      <title>brew_crew</title>
      <link rel="manifest" href="manifest.json">
    </head>
    <body>
      <!-- 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>
        var serviceWorkerVersion = null;
        var scriptLoaded = false;
        function loadMainDartJs() {
      if (scriptLoaded) {
        return;
      }
      scriptLoaded = true;
      var scriptTag = document.createElement('script');
      scriptTag.src = 'main.dart.js';
      scriptTag.type = 'application/javascript';
      document.body.append(scriptTag);
    }

    if ('serviceWorker' in navigator) {
      // Service workers are supported. Use them.
      window.addEventListener('load', function () {
        // Wait for registration to finish before dropping the <script> tag.
        // Otherwise, the browser will load the script multiple times,
        // potentially different versions.
        var serviceWorkerUrl = 'flutter_service_worker.js?v=' + serviceWorkerVersion;
        navigator.serviceWorker.register(serviceWorkerUrl)
          .then((reg) => {
            function waitForActivation(serviceWorker) {
              serviceWorker.addEventListener('statechange', () => {
                if (serviceWorker.state == 'activated') {
                  console.log('Installed new service worker.');
                  loadMainDartJs();
                }
              });
            }
            if (!reg.active && (reg.installing || reg.waiting)) {
              // No active web worker and we have installed or are installing
              // one for the first time. Simply wait for it to activate.
              waitForActivation(reg.installing ?? reg.waiting);
            } else if (!reg.active.scriptURL.endsWith(serviceWorkerVersion)) {
              // When the app updates the serviceWorkerVersion changes, so we
              // need to ask the service worker to update.
              console.log('New service worker available.');
              reg.update();
              waitForActivation(reg.installing);
            } else {
              // Existing service worker is still good.
              console.log('Loading app from service worker.');
              loadMainDartJs();
            }
          });

        // If service worker doesn't succeed in a reasonable amount of time,
        // fallback to plaint <script> tag.
        setTimeout(() => {
          if (!scriptLoaded) {
            console.warn(
              'Failed to load app from service worker. Falling back to plain <script> tag.',
            );
            loadMainDartJs();
          }
        }, 4000);
      });
    } else {
      // Service workers not supported. Just drop the <script> tag.
      loadMainDartJs();
    }
  </script>
</body>
</html>

另外，如果您需要，您可以转到 git 存储库到其他文件。 https://github.com/rostikro/The-app

我使用的是 Flutter 2.0.2。

Answer 1

我查看了您的 Github 存储库链接，您的 index.html 缺少 Firebase JS 条目的实现。

您的 pubspec.yaml 文件包含以下依赖项：

  firebase_core: ^0.7.0
  firebase_auth: ^0.20.1
  cloud_firestore: ^0.16.0+1

但是您并没有告诉 index.html 导入它们。以下导入适用于 ^1.0.1 版本的 firebase_auth 和 cloud_firestore

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

请按照文档进行操作，他们对有关 Firebase 和 Flutter 的所有内容（特别是 here）进行了非常详尽而详尽的解释。您还提到您使用的是 Flutter 2.0.2 版本，请注意空值安全。

颤振网络错误。未捕获的 ReferenceError：firebase 未定义

1 个答案: