如何将 Flutter 项目迁移到 Firebase 版本 9 现代 Web 模块化风格
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【中文标题】如何将 Flutter 项目迁移到 Firebase 版本 9 现代 Web 模块化风格【英文标题】：How to migrate Flutter project to Firebase version-9 modern web modular style 【发布时间】：2021-11-03 17:35:07 【问题描述】：我在初始化 Firebase 和 Flutter 项目时遇到问题，而我刚刚将我的 firebase-tools 和 firebase 更新到 版本 9 这是 现代网络模块化风格 并且已经一周没有任何帮助 Flutter 的文档仍然根据旧式兼容类型的版本 8 并且当我关注更新其抛出错误的 firebase 文档时颤振。我需要你的帮助 firebase 和颤振专家请提供一些解决方案。
我得到的两个错误是，
core.dart:56 Uncaught (in promise) TypeError: Cannot read properties of undefined (reading 'app')
at Object.app$ [as app] (core.dart:56)
at initializeApp (firebase_core_web.dart:68)
at initializeApp.next (<anonymous>)
at runBody (async_patch.dart:84)
at Object._async [as async] (async_patch.dart:123)
at firebase_core_web.FirebaseCoreWeb.new.initializeApp (firebase_core_web.dart:28)
at initializeApp (firebase.dart:42)
at initializeApp.next (<anonymous>)
at runBody (async_patch.dart:84)
at Object._async [as async] (async_patch.dart:123)
at Function.initializeApp (firebase.dart:38)
at main$ (main.dart:9)
at main$.next (<anonymous>)
at runBody (async_patch.dart:84)
at Object._async [as async] (async_patch.dart:123)
at main$ (main.dart:7)
at main (web_entrypoint.dart:19)
at main.next (<anonymous>)
at async_patch.dart:45
at _RootZone.runUnary (zone.dart:1613)
at _FutureListener.thenAwait.handleValue (future_impl.dart:155)
at handleValueCallback (future_impl.dart:707)
at Function._propagateToListeners (future_impl.dart:736)
at _Future.new.[_completeWithValue] (future_impl.dart:542)
at future.dart:401
at _RootZone.runUnary (zone.dart:1613)
at _FutureListener.then.handleValue (future_impl.dart:155)
at handleValueCallback (future_impl.dart:707)
at Function._propagateToListeners (future_impl.dart:736)
at _Future.new.[_completeWithValue] (future_impl.dart:542)
at async._AsyncCallbackEntry.new.callback (future_impl.dart:580)
at Object._microtaskLoop (schedule_microtask.dart:40)
at _startMicrotaskLoop (schedule_microtask.dart:49)
at async_patch.dart:166
和
══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
js_primitives.dart:30 The following JSNoSuchMethodError was thrown building MyApp(dirty):
js_primitives.dart:30 TypeError: Cannot read properties of undefined (reading 'app')
js_primitives.dart:30
js_primitives.dart:30 The relevant error-causing widget was:
js_primitives.dart:30 MyApp file:///C:/Users/Neha/androidStudioProjects/devcom/lib/main.dart:10:10
js_primitives.dart:30
js_primitives.dart:30 When the exception was thrown, this was the stack:
js_primitives.dart:30 C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/errors.dart 236:49 throw_
js_primitives.dart:30 packages/firebase_core_web/firebase_core_web.dart 73:3 _catchJSError
js_primitives.dart:30 packages/firebase_core_web/src/firebase_core_web.dart 138:13 app
js_primitives.dart:30 packages/firebase_core/src/firebase.dart 55:41 app
js_primitives.dart:30 packages/firebase_auth/src/firebase_auth.dart 38:47 get instance
js_primitives.dart:30 packages/devcom/auth.dart 12:51 new
js_primitives.dart:30 packages/devcom/main.dart 17:13 build
js_primitives.dart:30 packages/flutter/src/widgets/framework.dart 4648:28 build
js_primitives.dart:30 packages/flutter/src/widgets/framework.dart 4574:15 performRebuild
js_primitives.dart:30 packages/flutter/src/widgets/framework.dart 4267:5 rebuild
js_primitives.dart:30 packages/flutter/src/widgets/framework.dart 4553:5 [_firstBuild]
js_primitives.dart:30 packages/flutter/src/widgets/framework.dart 4548:5 mount
js_primitives.dart:30 packages/flutter/src/widgets/framework.dart 3611:13 inflateWidget
js_primitives.dart:30 packages/flutter/src/widgets/framework.dart 3363:18 updateChild
js_primitives.dart:30 packages/flutter/src/widgets/binding.dart 1189:16 [_rebuild]
js_primitives.dart:30 packages/flutter/src/widgets/binding.dart 1159:5 mount
js_primitives.dart:30 packages/flutter/src/widgets/binding.dart 1104:16 <fn>
js_primitives.dart:30 packages/flutter/src/widgets/framework.dart 2535:19 buildScope
js_primitives.dart:30 packages/flutter/src/widgets/binding.dart 1103:12 attachToRenderTree
js_primitives.dart:30 packages/flutter/src/widgets/binding.dart 936:24 attachRootWidget
js_primitives.dart:30 packages/flutter/src/widgets/binding.dart 917:7 <fn>
js_primitives.dart:30 C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/isolate_helper.dart 48:19 internalCallback
js_primitives.dart:30
js_primitives.dart:30 ════════════════════════════════════════════════════════════════════════════════════════════════════
main.dart：
import 'package:flutter/material.dart';
import 'package:devcom/auth.dart';
import 'package:devcom/auth_provider.dart';
import 'package:devcom/root_page.dart';
import 'package:firebase_core/firebase_core.dart';
void main() async
WidgetsFlutterBinding.ensureInitialized();
Firebase.initializeApp();
runApp(MyApp());
class MyApp extends StatelessWidget
@override
Widget build(BuildContext context)
return AuthProvider(
auth: Auth(),
child: MaterialApp(
title: 'Flutter login demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: RootPage(),
),
);
index.html：
<!DOCTYPE html>
<html>
<head>
<!-- <script src="https://www.gstatic.com/firebasejs/9.0.1/firebase-app.js" type = "module"></script>
<script src="https://www.gstatic.com/firebasejs/9.0.1/firebase-analytics.js" type = "module"> </script>
<script src="https://www.gstatic.com/firebasejs/9.0.1/firebase-auth.js" type = "module"></script> -->
<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="devcom">
<link rel="apple-touch-icon" href="icons/Icon-192.png">
<!-- Favicon -->
<link rel="shortcut icon" type="image/png" href="favicon.png" />
<title>Devcom</title>
<link rel="manifest" href="manifest.json">
</head>
<body >
<!-- The core Firebase JS SDK is always required and must be listed first -->
<script type="module">
import initializeApp from 'https://www.gstatic.com/firebasejs/9.0.1/firebase-app.js';
import from 'https://www.gstatic.com/firebasejs/9.0.1/firebase-auth.js';
import getAnalytics from "https://www.gstatic.com/firebasejs/9.0.1/firebase-analytics.js";
const firebaseConfig =
apiKey: "...",
authDomain: "......",
databaseURL: ".....",
projectId: "...",
storageBucket: "",
messagingSenderId: "",
measurementId: "",
appId: "1:.........:web:...........",
;
const app = initializeApp( firebaseConfig );
// const app = getAnalytics( firebaseConfig )
</script>
<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>【问题讨论】：
【参考方案1】：Firebase 的 Flutter Web 绑定构建在 v9 之前的 API 之上。据我在 Github 存储库中看到的，还没有 discussion 开始将它们移植到 v9。我建议将它留给库的作者来决定何时迁移到 v9 模块化 API 样式的最佳时间，并在此之前使用 v8，如 adding the Firebase SDKs to your web app 上的 FlutterFire 文档中所示。
如果您坚持已经迁移到 v9，则可以使用其 -compat 构建，它将以前的 API 样式固定在新的模块化版本上。这将允许您使用最新版本，尽管它不会为您提供新模块化 API 的（完整）大小优势。
【讨论】：
我是 firebase 新手，那么如何将我的 firebase 版本降级到 flutter 支持的版本，目前我猜是 8.6.1 或使用 comat version-9 of firebase with flutter 是否使用 npm 卸载 Firebase 并再次安装以确保它与 Flutter 兼容，否则我们需要指定它 我链接的文档准确显示了要添加的内容，确实是 8.6.1 版，例如<script src="https://www.gstatic.com/firebasejs/8.6.1/firebase-app.js"></script>。完成此操作后，您还可以使用代码 sn-p 来初始化该页面上显示的 Firebase。【参考方案2】：
您的颤振代码不符合文档的建议，尤其是在哪里以及如何调用 Firebase.initializeApp();。
这是直接来自docs的sn-p：
import 'package:flutter/material.dart';
// Import the firebase_core plugin
import 'package:firebase_core/firebase_core.dart';
void main()
WidgetsFlutterBinding.ensureInitialized();
runApp(App());
/// We are using a StatefulWidget such that we only create the [Future] once,
/// no matter how many times our widget rebuild.
/// If we used a [StatelessWidget], in the event where [App] is rebuilt, that
/// would re-initialize FlutterFire and make our application re-enter loading state,
/// which is undesired.
class App extends StatefulWidget
// Create the initialization Future outside of `build`:
@override
_AppState createState() => _AppState();
class _AppState extends State<App>
/// The future is part of the state of our widget. We should not call `initializeApp`
/// directly inside [build].
final Future<FirebaseApp> _initialization = Firebase.initializeApp();
@override
Widget build(BuildContext context)
return FutureBuilder(
// Initialize FlutterFire:
future: _initialization,
builder: (context, snapshot)
// Check for errors
if (snapshot.hasError)
return SomethingWentWrong();
// Once complete, show your application
if (snapshot.connectionState == ConnectionState.done)
return MyAwesomeApp();
// Otherwise, show something whilst waiting for initialization to complete
return Loading();
,
);
如您所见，该函数在调用 runApp(App()); 之后被调用。
Firebase.initializeApp(); 不仅返回 Future<FirebaseApp>（您的代码中没有 await），它还是主小部件状态的一部分。
【讨论】：
我按照你的建议做了，现在所有错误都消失了，但现在它执行第一个if statement 条件为 snapshot.hasError 并返回 SomethingWentWrong() 代码
谢谢他现在工作的问题原因是main.dart中的'auth'以上是关于如何将 Flutter 项目迁移到 Firebase 版本 9 现代 Web 模块化风格的主要内容，如果未能解决你的问题，请参考以下文章
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