Flutter集成Firebase注册出现_AssertionError问题求助

你碰到的这个_AssertionError ('package:firebase_auth/src/firebase_auth.dart': Failed assertion: line 95 pos 12: 'email != null': is not true.)崩溃，问题根源完全和你推测的一致——TextFormField的onSaved逻辑没正确更新类里的成员变量，导致传给Firebase的email和password都是null，触发了断言检查。

为什么原来的代码会失效？ #

你在buildTextField方法里把_saved作为参数传递，但Dart里的String是值类型，在onSaved: (input) => _saved = input这行里，你只是修改了方法内部的局部变量副本，根本没碰到底层类的_email、_password这些成员变量。所以调用form.save()后，这些变量依然是null，传给Firebase接口时自然就炸了。

修复方案 #

我们需要让onSaved直接操作类成员变量，最灵活的方式是给buildTextField传入一个赋值回调函数，具体步骤如下：

1. 修改buildTextField方法定义

移除没用的_saved参数，新增一个Function(String)类型的onSaved回调参数：

Widget buildTextField(
    double width,
    String text,
    IconData icon,
    bool obscureText,
    String isEmpty,
    bool autoValidate,
    Function(String) onSaved, // 新增回调参数
){
  return Container(
    margin: EdgeInsets.only(bottom: 15),
    width: width * 0.9,
    child: TextFormField(
      validator: (input) => input.isEmpty ? isEmpty : null,
      onSaved: onSaved, // 直接使用传入的回调
      autovalidate: autoValidate,
      obscureText: obscureText,
      decoration: InputDecoration(
        suffixIcon: Padding(
          padding: EdgeInsetsDirectional.only(end: 12.0),
          child: Icon(icon, color: Colors.red),
        ),
        hintText: text,
        hintStyle: TextStyle(color: Colors.redAccent, fontSize: 15.0),
        border: OutlineInputBorder(
          borderRadius: BorderRadius.circular(30.0),
          borderSide: BorderSide(
            width: 5.0,
            color: Colors.redAccent,
          ),
        ),
      ),
    ),
  );
}

2. 调用buildTextField时传入对应回调

每个TextField传入直接赋值给类成员的回调：

buildTextField(width, "Digite seu nome", Icons.person, false, "Por favor, digite seu nome!", _autoValidate, (input) => _displayName = input),
buildTextField(width, "Digite seu e-mail", Icons.email, false, "Por favor, digite seu e-mail!", _autoValidate, (input) => _email = input),
buildTextField(width, "Digite sua senha", Icons.lock, true, "Por favor, digite sua senha!", _autoValidate, (input) => _password = input),
buildTextField(width, "Confirme sua senha", Icons.lock, true, "Por favor, confirme sua senha!", _autoValidate, (input) => _passwordConfirm = input),

3. 增强注册逻辑的健壮性

在_validateSubmitRegister里加上密码校验和异常处理，避免更多潜在问题：

void _validateSubmitRegister() async{
  final form = formKey.currentState;
  if (form.validate()) {
    form.save();
    // 新增密码一致性校验
    if(_password != _passwordConfirm){
      scaffoldKey.currentState.showSnackBar(SnackBar(content: Text("Senhas não coincidem!")));
      return;
    }
    try{
      setState(() => _loading = true);
      AuthResult result = await FirebaseAuth.instance.createUserWithEmailAndPassword(email: _email, password: _password);
      FirebaseUser user = result.user;
      // 可选：更新用户的displayName到Firebase Auth
      await user.updateProfile(displayName: _displayName);
      // 注册成功后跳转到主页（替换成你的目标页面）
      Navigator.pushReplacement(context, MaterialPageRoute(builder: (context) => MyApp()));
    }catch(e){
      setState(() => _loading = false);
      scaffoldKey.currentState.showSnackBar(SnackBar(content: Text("Erro ao registrar: ${e.toString()}")));
    }
  } else {
    setState(() => _autoValidate = true);
  }
}

完整修复后的代码 #

import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:flutter/material.dart';
import 'package:cruke_app/main.dart';
import 'package:cruke_app/ui/login.dart';

class CrukeRegister extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Register(),
    );
  }
}

class Register extends StatefulWidget {
  @override
  _RegisterState createState() => _RegisterState();
}

class _RegisterState extends State<Register> {
  String _email, _password, _passwordConfirm, _displayName;
  final formKey = new GlobalKey<FormState>();
  bool _autoValidate = false;
  final FirebaseAuth auth = FirebaseAuth.instance;
  bool _loading = false;
  final scaffoldKey = new GlobalKey<ScaffoldState>();

  @override
  void initState() {
    super.initState();
  }

  Widget buildTextField(
      double width,
      String text,
      IconData icon,
      bool obscureText,
      String isEmpty,
      bool autoValidate,
      Function(String) onSaved,
  ){
    return Container(
      margin: EdgeInsets.only(bottom: 15),
      width: width * 0.9,
      child: TextFormField(
        validator: (input) => input.isEmpty ? isEmpty : null,
        onSaved: onSaved,
        autovalidate: autoValidate,
        obscureText: obscureText,
        decoration: InputDecoration(
          suffixIcon: Padding(
            padding: EdgeInsetsDirectional.only(end: 12.0),
            child: Icon(icon, color: Colors.red),
          ),
          hintText: text,
          hintStyle: TextStyle(color: Colors.redAccent, fontSize: 15.0),
          border: OutlineInputBorder(
            borderRadius: BorderRadius.circular(30.0),
            borderSide: BorderSide(
              width: 5.0,
              color: Colors.redAccent,
            ),
          ),
        ),
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    double width = MediaQuery.of(context).size.width;
    double height = MediaQuery.of(context).size.height;
    return Scaffold(
      key: scaffoldKey,
      backgroundColor: Colors.white,
      body: SingleChildScrollView(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Center(
              child: Container(
                margin: EdgeInsets.only(top: height * 0.025),
                child: Image.asset("images/logo_vertical.png", width: width * 0.5),
              ),
            ),
            Form(
              key: formKey,
              autovalidate: _autoValidate,
              child: Column(
                children: <Widget>[
                  buildTextField(width, "Digite seu nome", Icons.person, false, "Por favor, digite seu nome!", _autoValidate, (input) => _displayName = input),
                  buildTextField(width, "Digite seu e-mail", Icons.email, false, "Por favor, digite seu e-mail!", _autoValidate, (input) => _email = input),
                  buildTextField(width, "Digite sua senha", Icons.lock, true, "Por favor, digite sua senha!", _autoValidate, (input) => _password = input),
                  buildTextField(width, "Confirme sua senha", Icons.lock, true, "Por favor, confirme sua senha!", _autoValidate, (input) => _passwordConfirm = input),
                  Container(
                    height: height * 0.09,
                    width: width * 0.9,
                    padding: EdgeInsets.only(top: 10.0),
                    child: RaisedButton.icon(
                      onPressed: _validateSubmitRegister,
                      label: Text(
                        'Registrar',
                        style: TextStyle(fontSize: 15, color: Colors.white),
                      ),
                      color: Colors.red,
                      icon: Icon(Icons.account_circle, color: Colors.white),
                      shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(30.0)),
                    ),
                  ),
                ],
              ),
            ),
            Container(
              margin: EdgeInsets.only(top: 15),
              child: Material(
                child: InkWell(
                  onTap: (){
                    Navigator.push(context, MaterialPageRoute(builder: (context) => CrukeLogin()));
                  },
                  child: Text("Já tem uma conta? Faça Login!", style: TextStyle(fontSize: 15, color: Colors.red),),
                ),
              ),
            ),
          ],
        ),
      ),
    );
  }

  void _validateSubmitRegister() async{
    final form = formKey.currentState;
    if (form.validate()) {
      form.save();
      if(_password != _passwordConfirm){
        scaffoldKey.currentState.showSnackBar(SnackBar(content: Text("Senhas não coincidem!")));
        return;
      }
      try{
        setState(() => _loading = true);
        AuthResult result = await FirebaseAuth.instance.createUserWithEmailAndPassword(email: _email, password: _password);
        FirebaseUser user = result.user;
        await user.updateProfile(displayName: _displayName);
        Navigator.pushReplacement(context, MaterialPageRoute(builder: (context) => MyApp()));
      }catch(e){
        setState(() => _loading = false);
        scaffoldKey.currentState.showSnackBar(SnackBar(content: Text("Erro ao registrar: ${e.toString()}")));
      }
    } else {
      setState(() => _autoValidate = true);
    }
  }
}

这样修改后，form.save()就能正确把输入值赋值给类成员变量，Firebase接口也能拿到有效的email和password，崩溃问题就解决了。额外增加的密码校验和异常处理也能让注册流程更顺畅。

内容的提问来源于stack exchange，提问作者Rafael Canuto