Flutter邮箱密码注册时如何将UID与Email存入SharedPreferences

解决方案 #

1. 修复SignInProvider的变量赋值问题 #

原saveDataToSharedPreferences方法依赖类内的_email和_uid变量，但邮箱注册时没给这两个变量赋值，直接调用会触发空指针异常。给SignInProvider新增更新用户信息的方法：

class SignInProvider extends ChangeNotifier {
  // ... 原有代码不变 ...

  // 新增：更新Provider内的用户UID和Email
  Future updateUserInfo(String uid, String email) async {
    _uid = uid;
    _email = email;
    notifyListeners();
  }

  // 可选优化：让saveData支持直接传参（避免依赖类内变量）
  Future saveDataToSharedPreferences({String? uid, String? email}) async {
    final SharedPreferences s = await SharedPreferences.getInstance();
    await s.setString('email', email ?? _email!);
    await s.setString('uid', uid ?? _uid!);
    notifyListeners();
  }
}

2. 重构邮箱注册方法 #

原代码错误地在createUserWithEmailAndPassword后链式调用Provider方法，createUserWithEmailAndPassword返回的是UserCredential，不是SignInProvider实例，所以会报错。修改后的注册方法：

void signUp(String email, String password) async {
  if (_formkey.currentState!.validate()) {
    try {
      // 执行邮箱密码注册
      UserCredential credential = await _auth.createUserWithEmailAndPassword(
        email: email,
        password: password,
      );
      
      if (credential.user != null) {
        final sp = context.read<SignInProvider>();
        // 更新Provider内的用户信息
        await sp.updateUserInfo(
          credential.user!.uid, 
          credential.user!.email!
        );
        // 保存到SharedPreferences并设置登录状态
        await sp.saveDataToSharedPreferences();
        await sp.setSignIn();
        // 写入Firestore
        await postDetailsToFirestore();
      }
    } catch (e) {
      Fluttertoast.showToast(msg: e.toString());
    }
  }
}

3. 优化postDetailsToFirestore（可选） #

直接从SignInProvider获取用户信息，不用重复调用_auth.currentUser：

postDetailsToFirestore() async {
  FirebaseFirestore firebaseFirestore = FirebaseFirestore.instance;
  final sp = context.read<SignInProvider>();

  UserModel userModel = UserModel();
  userModel.email = sp.email;
  userModel.uid = sp.uid;

  await firebaseFirestore
      .collection("users")
      .doc(sp.uid)
      .set(userModel.toMap());

  Fluttertoast.showToast(msg: "Account created successfully ");
  Navigator.pushAndRemoveUntil(
    context,
    MaterialPageRoute(builder: (context) => HomeScreen()),
    (route) => false,
  );
}

4. 确保自动登录正常触发 #

应用启动时，SignInProvider的构造函数已经调用checkSignInUser，在启动页判断登录状态即可自动跳转：

@override
void initState() {
  super.initState();
  WidgetsBinding.instance.addPostFrameCallback((_) {
    final sp = context.read<SignInProvider>();
    if (sp.isSignedIn) {
      Navigator.pushReplacement(
        context, 
        MaterialPageRoute(builder: (_) => HomeScreen())
      );
    }
  });
}

内容的提问来源于stack exchange，提问作者Dasun Dola