Flutter注册表单无法提交至Firebase认证，Provider断言失败求助

API 探路者

2026-8-18

Flutter注册表单提交Firebase认证失败及Provider断言错误修复

问题说明

我是Flutter新手，开发移动应用时遇到两个问题：注册表单无法将数据提交到Firebase认证，同时触发Provider断言失败错误。

Auth类代码

class Auth with ChangeNotifier {
  late String _token;
  late DateTime _expirytDate;
  late String _userId;
  Future<void> signup(String email, String password) async {
    const url =
        'https://identitytoolkit.googleapis.com/v1/accounts:signInWithCustomToken?key=AIzaSyDL5WN64rhcYbYbiLutVA33Ekjixj0M3BE';
    final response = await http.post(Uri.parse(url),
        body: json.encode({
          'email': email,
          'password': password,
          'returnSecureToken': true,

        }));
  }
}

AuthCard类代码

class AuthCard extends StatefulWidget {
  @override
  _AuthCardState createState() => _AuthCardState();
}

class _AuthCardState extends State<AuthCard> {
  final GlobalKey<FormState> _formKey = GlobalKey();
  AuthMode _authMode = AuthMode.Login;
  Map<String, String> _authData = {
    'email': '',
    'password': '',
  };
  var _isLoading = false;
  final _passwordController = TextEditingController();

  Future<void> _submit() async {
    if (!_formKey.currentState!.validate()) {
      // Invalid!
      return;
    }
     _formKey.currentState!.save();
    setState(() {
      _isLoading = true;
    });
    if (_authMode == AuthMode.Login) {
      // Log user in
    } else {
      // Sign user up
     await  Provider.of<Auth>(context).signup(_authData['email']! ,_authData['password']!   );
    }
    setState(() {
      _isLoading = false;
    });
  }

  void _switchAuthMode() {
    if (_authMode == AuthMode.Login) {
      setState(() {
        _authMode = AuthMode.Signup;
      });
    } else {
      setState(() {
        _authMode = AuthMode.Login;
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    final deviceSize = MediaQuery.of(context).size;
    return Card(
      shape: RoundedRectangleBorder(
        borderRadius: BorderRadius.circular(10.0),
      ),
      elevation: 8.0,
      child: Container(
        height: _authMode == AuthMode.Signup ? 320 : 260,
        constraints:
            BoxConstraints(minHeight: _authMode == AuthMode.Signup ? 320 : 260),
        width: deviceSize.width * 0.75,
        padding: EdgeInsets.all(16.0),
        child: Form(
          key: _formKey,
          child: SingleChildScrollView(
            child: Column(
              children: <Widget>[
                TextFormField(
                  decoration: InputDecoration(labelText: 'E-Mail'),
                  keyboardType: TextInputType.emailAddress,
                  validator: (value) {
                    if (value!.isEmpty || !value.contains('@')) {
                      return 'Invalid email!';
                    }
                    return null;
                  },
                  onSaved: (value) {
                    _authData['email'] = value!;
                  },
                ),
                TextFormField(
                  decoration: InputDecoration(labelText: 'Password'),
                  obscureText: true,
                  controller: _passwordController,
                  validator: (value) {
                    if (value!.isEmpty || value.length < 5) {
                      return 'Password is too short!';
                    }
                  },
                  onSaved: (value) {
                    _authData['password'] = value!;
                  },
                ),
                if (_authMode == AuthMode.Signup)
                  TextFormField(
                    enabled: _authMode == AuthMode.Signup,
                    decoration: InputDecoration(labelText: 'Confirm Password'),
                    obscureText: true,
                    validator: _authMode == AuthMode.Signup
                        ? (value) {
                            if (value != _passwordController.text) {
                              return 'Passwords do not match!';
                            }
                          }
                        : null,
                  ),
                SizedBox(
                  height: 20,
                ),
                if (_isLoading)
                  CircularProgressIndicator()
                else
                  Padding(
                    padding: const EdgeInsets.all(8.0),
                    child: ElevatedButton(
                      child: Text(
                          _authMode == AuthMode.Login ? 'LOGIN' : 'SIGN UP'),
                      onPressed: _submit,
                    ),
                  ),
                TextButton(
                  child: Padding(
                    padding:
                        EdgeInsets.symmetric(horizontal: 30.0, vertical: 4),
                    child: Text(
                        '${_authMode == AuthMode.Login ? 'SIGNUP' : 'LOGIN'} INSTEAD'),
                  ),
                  onPressed: _switchAuthMode,
                  style: TextButton.styleFrom(primary: Colors.amber),
                ),
              ],
            ),
          ),
        ),
      ),
    );
  }
}

触发的错误信息

Error: Assertion failed:
file:///C:/Users/DELL/development/SDK/flutter/.pub-cache/hosted/pub.dartlang.org/provider-6.0.3/lib/src/provider.dart:274:7
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/errors.dart 266:49      throw_
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/errors.dart 29:3        assertFailed       
packages/provider/src/provider.dart 276:11
of
packages/flutter_application_1/screens/auth_screen.dart 114:40
_submit
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 84:54                runBody
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 123:5                _async
packages/flutter_application_1/screens/auth_screen.dart 101:23
[_submit]
packages/flutter/src/material/ink_well.dart 1072:21
handleTap
packages/flutter/src/gestures/recognizer.dart 253:24
invokeCallback
packages/flutter/src/gestures/tap.dart 627:11
handleTapUp
packages/flutter/src/gestures/tap.dart 306:5
[_checkUp]
packages/flutter/src/gestures/tap.dart 239:7
handlePrimaryPointer
packages/flutter/src/gestures/recognizer.dart 615:9
handleEvent
packages/flutter/src/gestures/pointer_router.dart 98:12
[_dispatch]
packages/flutter/src/gestures/pointer_router.dart 143:9
<fn>
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/linked_hash_map.dart 21:13          forEach
packages/flutter/src/gestures/pointer_router.dart 141:17
[_dispatchEventToRoutes]
packages/flutter/src/gestures/pointer_router.dart 127:7
route
packages/flutter/src/gestures/binding.dart 460:19
handleEvent
packages/flutter/src/gestures/binding.dart 440:14
dispatchEvent
packages/flutter/src/rendering/binding.dart 337:11
dispatchEvent
packages/flutter/src/gestures/binding.dart 395:7
[_handlePointerEventImmediately]
packages/flutter/src/gestures/binding.dart 357:5
handlePointerEvent
packages/flutter/src/gestures/binding.dart 314:7
[_flushPointerEventQueue]
packages/flutter/src/gestures/binding.dart 295:7
[_handlePointerDataPacket]
C:/b/s/w/ir/cache/builder/src/out/host_debug/flutter_web_sdk/lib/_engine/engine/platform_dispatcher.dart 1183:13               invoke1

解决方案

1. 修复Provider断言失败错误

Provider断言失败的核心原因是Widget树中没有上层提供Auth实例，且异步调用时未关闭监听。按以下步骤修改：

在App根组件（比如MaterialApp外层）添加ChangeNotifierProvider，确保Auth实例能被子组件访问：

void main() {
  runApp(
    ChangeNotifierProvider(
      create: (ctx) => Auth(),
      child: MyApp(),
    ),
  );
}

在_submit方法中调用Provider时，添加listen: false（仅调用方法无需监听状态变化）：
```
await Provider.of<Auth>(context, listen: false).signup(_authData['email']!, _authData['password']!);
```

2. 修复Firebase认证提交失败问题

当前Auth类使用的Firebase接口错误，注册需使用用户创建接口而非自定义令牌登录接口：

将signup方法中的URL替换为注册接口：

const url = 'https://identitytoolkit.googleapis.com/v1/accounts:signUp?key=AIzaSyDL5WN64rhcYbYbiLutVA33Ekjixj0M3BE';

添加响应错误处理，避免静默失败：

final responseData = json.decode(response.body);
if (response.statusCode >= 400) {
  throw Exception(responseData['error']['message']);
} else {
  _token = responseData['idToken'];
  _userId = responseData['localId'];
  _expirytDate = DateTime.now().add(
    Duration(seconds: int.parse(responseData['expiresIn'])),
  );
  notifyListeners();
}

内容的提问来源于stack exchange，提问作者LeThanhDat

Flutter注册表单无法提交至Firebase认证，Provider断言失败求助

问题说明 #

Auth类代码 #

AuthCard类代码 #

触发的错误信息 #

解决方案 #

1. 修复Provider断言失败错误 #

2. 修复Firebase认证提交失败问题 #