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错误：[core/no-app] no Firebase App＆＃x27; [默认]＆＃x27;已创建 - 致电firebase.initializeapp（）

发布于 2025-01-24 02:04:28 字数 9558 浏览 0 评论 0原文

我正在构建一个颤抖的应用程序，并且已经集成了Firebase，但是当我单击登录按钮时，我会遇到此错误。我遇到了有类似问题的人，但似乎没有人对我有用。我正在使用VS代码作为我的IDE。如何解决此问题？

这是我每个文件的代码...

main.dart文件


import 'login_screen.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      debugShowCheckedModeBanner: false,
      title: "FLUTTER-FIREBASE LOGIN APP",
      home: LoginScreen(),
    );
  }
}

login_screen.dart文件

import 'package:firebase_core/firebase_core.dart';
import 'package:flutter/material.dart';

import 'profile_screen.dart';

class LoginScreen extends StatefulWidget {
  const LoginScreen({Key? key}) : super(key: key);

  @override
  State<LoginScreen> createState() => _LoginScreenState();
}

class _LoginScreenState extends State<LoginScreen> {
  // Initialize Firebase App
  Future<FirebaseApp> _initializeFirebase() async {
    FirebaseApp firebaseApp = await Firebase.initializeApp();
    return firebaseApp;
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: FutureBuilder(
        future: _initializeFirebase(),
        builder: (context, snapshot) {
          if (snapshot.connectionState == ConnectionState.done) {
            return const LoginForm();
          }
          return const Center(
            child: CircularProgressIndicator(),
          );
        },
      ),
    );
  }
}

class LoginForm extends StatefulWidget {
  const LoginForm({Key? key}) : super(key: key);

  @override
  State<LoginForm> createState() => _LoginFormState();
}

class _LoginFormState extends State<LoginForm> {
  // Login Function
  static Future<User?> loginUsingEmailPassword(
      {required String email,
      required String password,
      required BuildContext context}) async {
    FirebaseAuth auth = FirebaseAuth.instance;
    User? user;

    try {
      UserCredential userCredential = await auth.signInWithEmailAndPassword(
        email: email, 
        password: password,
      );
      user = userCredential.user;
    } on FirebaseAuthException catch (e) {
      if (e.code == "user-not-found") {
        print("No user found for that email");
      }
    }

    return user;
  }

  @override
  Widget build(BuildContext context) {
    // TextFielf Controller
    TextEditingController _emailController = TextEditingController();
    TextEditingController _passwordController = TextEditingController();

    return Padding(
      padding: const EdgeInsets.all(16.0),
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        crossAxisAlignment: CrossAxisAlignment.start,
        children: <Widget>[
          const Text(
            "MyApp Title",
            style: TextStyle(
              color: Colors.black,
              fontSize: 28,
              fontWeight: FontWeight.bold,
            ),
          ),
          const Text(
            "Login to your App",
            style: TextStyle(
              color: Colors.black,
              fontSize: 44.0,
              fontWeight: FontWeight.bold,
            ),
          ),
          const SizedBox(
            height: 44.0,
          ),
          TextField(
            controller: _emailController,
            keyboardType: TextInputType.emailAddress,
            decoration: const InputDecoration(
                hintText: "enter email...",
                prefixIcon: Icon(
                  Icons.mail,
                  color: Colors.black,
                )),
          ),
          const SizedBox(
            height: 26.0,
          ),
          TextField(
            controller: _passwordController,
            obscureText: true,
            decoration: const InputDecoration(
              hintText: "enter password...",
              prefixIcon: Icon(
                Icons.lock,
                color: Colors.black,
              ),
            ),
          ),
          const SizedBox(
            height: 12.0,
          ),
          const Text(
            "Forgot Password?",
            style: TextStyle(
              color: Colors.blue,
            ),
          ),
          const SizedBox(
            height: 88.0,
          ),
          Container(
            width: double.infinity,
            child: RawMaterialButton(
              fillColor: const Color(0xFF0069FE),
              elevation: 0.0,
              padding: const EdgeInsets.symmetric(vertical: 20.0),
              shape: RoundedRectangleBorder(
                borderRadius: BorderRadius.circular(12.0),
              ),
              onPressed: () async {
                User? user = await loginUsingEmailPassword(
                    email: _emailController.text,
                    password: _passwordController.text,
                    context: context);
                print(user);

                if (user != null) {
                  Navigator.of(context).pushReplacement(
                    MaterialPageRoute(builder: (context) => const ProfileScreen()));
                }
              },
              child: const Text(
                "Login",
                style: TextStyle(
                  color: Colors.white,
                  fontSize: 18.0,
                  fontWeight: FontWeight.bold,
                ),
              ),
            ),
          )
        ],
      ),
    );
  }
}

profile_screen.dart



class ProfileScreen extends StatefulWidget {
  const ProfileScreen({ Key? key }) : super(key: key);

  @override
  State<ProfileScreen> createState() => _ProfileScreenState();
}

class _ProfileScreenState extends State<ProfileScreen> {
  @override
  Widget build(BuildContext context) {
    return const Scaffold(
      body: Center(
        child: Text("TO BE CONTINUED...!!!"),
      ),
    );
  }
}```



**This is the error message I get when I tap on the login button**

Error: [core/no-app] No Firebase App '[DEFAULT]' has been created - call Firebase.initializeApp()
    at Object.throw_ [as throw] (http://localhost:51555/dart_sdk.js:5067:11)
at firebase_core_web.FirebaseCoreWeb.new.app (http://localhost:51555/packages/firebase_core_web/firebase_core_web.dart.lib.js:285:23)
at Function.app (http://localhost:51555/packages/firebase_core/firebase_core.dart.lib.js:111:50)
at Function.get instance [as instance] (http://localhost:51555/packages/firebase_auth/firebase_auth.dart.lib.js:96:55)
at loginUsingEmailPassword (http://localhost:51555/packages/flutter_login_with_firebase_authentication/login_screen.dart.lib.js:1047:47)
    at loginUsingEmailPassword.next (<anonymous>)
    at runBody (http://localhost:51555/dart_sdk.js:40590:34)
    at Object._async [as async] (http://localhost:51555/dart_sdk.js:40621:7)
at Function.loginUsingEmailPassword (http://localhost:51555/packages/flutter_login_with_firebase_authentication/login_screen.dart.lib.js:1046:20)
at http://localhost:51555/packages/flutter_login_with_firebase_authentication/login_screen.dart.lib.js:1068:66
    at Generator.next (<anonymous>)
    at runBody (http://localhost:51555/dart_sdk.js:40590:34)
    at Object._async [as async] (http://localhost:51555/dart_sdk.js:40621:7)
at http://localhost:51555/packages/flutter_login_with_firebase_authentication/login_screen.dart.lib.js:1067:1029
at ink_well._InkResponseState.new.[_handleTap] (http://localhost:51555/packages/flutter/src/material/icon_button.dart.lib.js:40468:31)
at tap.TapGestureRecognizer.new.invokeCallback (http://localhost:51555/packages/flutter/src/gestures/recognizer.dart.lib.js:190:18)
    at LinkedMap.new.forEach (http://localhost:51555/dart_sdk.js:27679:11)
at pointer_router.PointerRouter.new.[_dispatchEventToRoutes] (http://localhost:51555/packages/flutter/src/gestures/pointer_router.dart.lib.js:110:29)
at pointer_router.PointerRouter.new.route (http://localhost:51555/packages/flutter/src/gestures/pointer_router.dart.lib.js:105:37)
at binding$5.WidgetsFlutterBinding.new.handleEvent (http://localhost:51555/packages/flutter/src/gestures/binding.dart.lib.js:364:26)
at binding$5.WidgetsFlutterBinding.new.dispatchEvent (http://localhost:51555/packages/flutter/src/gestures/binding.dart.lib.js:352:24)
at binding$5.WidgetsFlutterBinding.new.dispatchEvent (http://localhost:51555/packages/flutter/src/rendering/layer.dart.lib.js:5427:13)
at binding$5.WidgetsFlutterBinding.new.[_handlePointerEventImmediately] (http://localhost:51555/packages/flutter/src/gestures/binding.dart.lib.js:328:14)
at binding$5.WidgetsFlutterBinding.new.handlePointerEvent (http://localhost:51555/packages/flutter/src/gestures/binding.dart.lib.js:302:43)
at binding$5.WidgetsFlutterBinding.new.[_flushPointerEventQueue] (http://localhost:51555/packages/flutter/src/gestures/binding.dart.lib.js:292:14)
at binding$5.WidgetsFlutterBinding.new.[_handlePointerDataPacket] (http://localhost:51555/packages/flutter/src/gestures/binding.dart.lib.js:283:54)
    at Object.invoke1 (http://localhost:51555/dart_sdk.js:190405:7)
    at _engine.EnginePlatformDispatcher.__.invokeOnPointerDataPacket (http://localhost:51555/dart_sdk.js:171081:15)
    at _engine.PointerBinding.__.[_onPointerData] (http://localhost:51555/dart_sdk.js:171963:49)
    at http://localhost:51555/dart_sdk.js:172401:28
    at http://localhost:51555/dart_sdk.js:172357:16
    at loggedHandler (http://localhost:51555/dart_sdk.js:172062:11)
原文

I am building a Flutter application and I have integrated Firebase, but I keep getting this error when I click on the login button. I have come across people with similar problem, but none seems to work for me. I am using VS Code as my IDE. How can I fix this problem?

Here is my code for each file...

main.dart file


import 'login_screen.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      debugShowCheckedModeBanner: false,
      title: "FLUTTER-FIREBASE LOGIN APP",
      home: LoginScreen(),
    );
  }
}

login_screen.dart file

import 'package:firebase_core/firebase_core.dart';
import 'package:flutter/material.dart';

import 'profile_screen.dart';

class LoginScreen extends StatefulWidget {
  const LoginScreen({Key? key}) : super(key: key);

  @override
  State<LoginScreen> createState() => _LoginScreenState();
}

class _LoginScreenState extends State<LoginScreen> {
  // Initialize Firebase App
  Future<FirebaseApp> _initializeFirebase() async {
    FirebaseApp firebaseApp = await Firebase.initializeApp();
    return firebaseApp;
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: FutureBuilder(
        future: _initializeFirebase(),
        builder: (context, snapshot) {
          if (snapshot.connectionState == ConnectionState.done) {
            return const LoginForm();
          }
          return const Center(
            child: CircularProgressIndicator(),
          );
        },
      ),
    );
  }
}

class LoginForm extends StatefulWidget {
  const LoginForm({Key? key}) : super(key: key);

  @override
  State<LoginForm> createState() => _LoginFormState();
}

class _LoginFormState extends State<LoginForm> {
  // Login Function
  static Future<User?> loginUsingEmailPassword(
      {required String email,
      required String password,
      required BuildContext context}) async {
    FirebaseAuth auth = FirebaseAuth.instance;
    User? user;

    try {
      UserCredential userCredential = await auth.signInWithEmailAndPassword(
        email: email, 
        password: password,
      );
      user = userCredential.user;
    } on FirebaseAuthException catch (e) {
      if (e.code == "user-not-found") {
        print("No user found for that email");
      }
    }

    return user;
  }

  @override
  Widget build(BuildContext context) {
    // TextFielf Controller
    TextEditingController _emailController = TextEditingController();
    TextEditingController _passwordController = TextEditingController();

    return Padding(
      padding: const EdgeInsets.all(16.0),
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        crossAxisAlignment: CrossAxisAlignment.start,
        children: <Widget>[
          const Text(
            "MyApp Title",
            style: TextStyle(
              color: Colors.black,
              fontSize: 28,
              fontWeight: FontWeight.bold,
            ),
          ),
          const Text(
            "Login to your App",
            style: TextStyle(
              color: Colors.black,
              fontSize: 44.0,
              fontWeight: FontWeight.bold,
            ),
          ),
          const SizedBox(
            height: 44.0,
          ),
          TextField(
            controller: _emailController,
            keyboardType: TextInputType.emailAddress,
            decoration: const InputDecoration(
                hintText: "enter email...",
                prefixIcon: Icon(
                  Icons.mail,
                  color: Colors.black,
                )),
          ),
          const SizedBox(
            height: 26.0,
          ),
          TextField(
            controller: _passwordController,
            obscureText: true,
            decoration: const InputDecoration(
              hintText: "enter password...",
              prefixIcon: Icon(
                Icons.lock,
                color: Colors.black,
              ),
            ),
          ),
          const SizedBox(
            height: 12.0,
          ),
          const Text(
            "Forgot Password?",
            style: TextStyle(
              color: Colors.blue,
            ),
          ),
          const SizedBox(
            height: 88.0,
          ),
          Container(
            width: double.infinity,
            child: RawMaterialButton(
              fillColor: const Color(0xFF0069FE),
              elevation: 0.0,
              padding: const EdgeInsets.symmetric(vertical: 20.0),
              shape: RoundedRectangleBorder(
                borderRadius: BorderRadius.circular(12.0),
              ),
              onPressed: () async {
                User? user = await loginUsingEmailPassword(
                    email: _emailController.text,
                    password: _passwordController.text,
                    context: context);
                print(user);

                if (user != null) {
                  Navigator.of(context).pushReplacement(
                    MaterialPageRoute(builder: (context) => const ProfileScreen()));
                }
              },
              child: const Text(
                "Login",
                style: TextStyle(
                  color: Colors.white,
                  fontSize: 18.0,
                  fontWeight: FontWeight.bold,
                ),
              ),
            ),
          )
        ],
      ),
    );
  }
}

profile_screen.dart



class ProfileScreen extends StatefulWidget {
  const ProfileScreen({ Key? key }) : super(key: key);

  @override
  State<ProfileScreen> createState() => _ProfileScreenState();
}

class _ProfileScreenState extends State<ProfileScreen> {
  @override
  Widget build(BuildContext context) {
    return const Scaffold(
      body: Center(
        child: Text("TO BE CONTINUED...!!!"),
      ),
    );
  }
}```



**This is the error message I get when I tap on the login button**

Error: [core/no-app] No Firebase App '[DEFAULT]' has been created - call Firebase.initializeApp()
    at Object.throw_ [as throw] (http://localhost:51555/dart_sdk.js:5067:11)
at firebase_core_web.FirebaseCoreWeb.new.app (http://localhost:51555/packages/firebase_core_web/firebase_core_web.dart.lib.js:285:23)
at Function.app (http://localhost:51555/packages/firebase_core/firebase_core.dart.lib.js:111:50)
at Function.get instance [as instance] (http://localhost:51555/packages/firebase_auth/firebase_auth.dart.lib.js:96:55)
at loginUsingEmailPassword (http://localhost:51555/packages/flutter_login_with_firebase_authentication/login_screen.dart.lib.js:1047:47)
    at loginUsingEmailPassword.next (<anonymous>)
    at runBody (http://localhost:51555/dart_sdk.js:40590:34)
    at Object._async [as async] (http://localhost:51555/dart_sdk.js:40621:7)
at Function.loginUsingEmailPassword (http://localhost:51555/packages/flutter_login_with_firebase_authentication/login_screen.dart.lib.js:1046:20)
at http://localhost:51555/packages/flutter_login_with_firebase_authentication/login_screen.dart.lib.js:1068:66
    at Generator.next (<anonymous>)
    at runBody (http://localhost:51555/dart_sdk.js:40590:34)
    at Object._async [as async] (http://localhost:51555/dart_sdk.js:40621:7)
at http://localhost:51555/packages/flutter_login_with_firebase_authentication/login_screen.dart.lib.js:1067:1029
at ink_well._InkResponseState.new.[_handleTap] (http://localhost:51555/packages/flutter/src/material/icon_button.dart.lib.js:40468:31)
at tap.TapGestureRecognizer.new.invokeCallback (http://localhost:51555/packages/flutter/src/gestures/recognizer.dart.lib.js:190:18)
    at LinkedMap.new.forEach (http://localhost:51555/dart_sdk.js:27679:11)
at pointer_router.PointerRouter.new.[_dispatchEventToRoutes] (http://localhost:51555/packages/flutter/src/gestures/pointer_router.dart.lib.js:110:29)
at pointer_router.PointerRouter.new.route (http://localhost:51555/packages/flutter/src/gestures/pointer_router.dart.lib.js:105:37)
at binding$5.WidgetsFlutterBinding.new.handleEvent (http://localhost:51555/packages/flutter/src/gestures/binding.dart.lib.js:364:26)
at binding$5.WidgetsFlutterBinding.new.dispatchEvent (http://localhost:51555/packages/flutter/src/gestures/binding.dart.lib.js:352:24)
at binding$5.WidgetsFlutterBinding.new.dispatchEvent (http://localhost:51555/packages/flutter/src/rendering/layer.dart.lib.js:5427:13)
at binding$5.WidgetsFlutterBinding.new.[_handlePointerEventImmediately] (http://localhost:51555/packages/flutter/src/gestures/binding.dart.lib.js:328:14)
at binding$5.WidgetsFlutterBinding.new.handlePointerEvent (http://localhost:51555/packages/flutter/src/gestures/binding.dart.lib.js:302:43)
at binding$5.WidgetsFlutterBinding.new.[_flushPointerEventQueue] (http://localhost:51555/packages/flutter/src/gestures/binding.dart.lib.js:292:14)
at binding$5.WidgetsFlutterBinding.new.[_handlePointerDataPacket] (http://localhost:51555/packages/flutter/src/gestures/binding.dart.lib.js:283:54)
    at Object.invoke1 (http://localhost:51555/dart_sdk.js:190405:7)
    at _engine.EnginePlatformDispatcher.__.invokeOnPointerDataPacket (http://localhost:51555/dart_sdk.js:171081:15)
    at _engine.PointerBinding.__.[_onPointerData] (http://localhost:51555/dart_sdk.js:171963:49)
    at http://localhost:51555/dart_sdk.js:172401:28
    at http://localhost:51555/dart_sdk.js:172357:16
    at loggedHandler (http://localhost:51555/dart_sdk.js:172062:11)

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评论（1）

梦途 2025-01-31 02:04:28

使用最近的firebase版本，您必须使用 firebase cli 连接您的应用程序。

通过运行以下命令来安装CLI首先安装Firebase CLI

Firebase CLI CLI CLI：

npm install -G firebase -tools

接下来，通过运行以下命令安装FlutterFire CLI：

dart dart pub global gobl FlutterFire_Cli

安装后，FlutterFire命令将在全球上可用。

在应用程序的词根中，运行configure命令：

FlutterFire configure

配置命令将指导您完成许多过程：

  • 选择firebase项目（基于.FireBaserc文件或Firebase Console） 。
  • 提示您想要配置的哪些平台（例如Android，iOS，macos＆amp; web）。
  • 确定应使用哪些firebase应用程序来提取配置。默认情况下，CLI将尝试根据您当前的项目配置自动匹配Firebase应用程序。
  • 在您的项目中生成firebase_options.dart文件。

完成后，您现在可以导入生成的文件并将其提供给InitializEapp方法：
lib/main.dart
//导入生成的文件
导入'firebase_options.dart';

然后，通过currentPlatform从defaultfirebaseoptions类提供当前平台选项：


void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  
await Firebase.initializeApp(
  options: DefaultFirebaseOptions.currentPlatform,
);
..

With the recent firebase versions you have to use Firebase Cli to connect your app.

Installing the cli first install firebase cli

Firebase CLI via npm by running the following command:

npm install -g firebase-tools

Next, install the FlutterFire CLI by running the following command:

dart pub global activate flutterfire_cli

Once installed, the flutterfire command will be globally available.

In the root of your application, run the configure command:

flutterfire configure

The configuration command will guide you through a number of processes:

  • Selecting a Firebase project (based on the .firebaserc file or from the Firebase Console).
  • Prompt what platforms (e.g. Android, iOS, macOS & web) you would like configuration for.
  • Identify which Firebase applications for the chosen platforms should be used to extract configuration for. By default, the CLI will attempt to automatically match Firebase apps based on your current project configuration.
  • Generate a firebase_options.dart file in your project.

Once complete, you can now import the generated file and provide it to the initializeApp method:
lib/main.dart
// Import the generated file
import 'firebase_options.dart';

Then, provide the current platform options via the currentPlatform getter from the DefaultFirebaseOptions class:


void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  
await Firebase.initializeApp(
  options: DefaultFirebaseOptions.currentPlatform,
);
..
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