如何获取当前的 Firebase UID 并将其写入实时数据库？

Posted 2023-02-23

【中文标题】如何获取当前的 Firebase UID 并将其写入实时数据库？

【英文标题】：How do I get the current Firebase UID and write it to Realtime Database?

【发布时间】：2022-01-17 06:12:38

【问题描述】：

我按照教程创建了这个 AuthService 类。这很好用。

import 'package:firebase_auth/firebase_auth.dart';
import 'package:app/models/user.dart' as UserModel;

class AuthService 

  final FirebaseAuth _auth = FirebaseAuth.instance;

  // create CurrentUser object based on Firebase user object
  UserModel.User? _userFromFirebaseUser(User? user) 
    // return user != null ? UserModel.User(uid: user.uid) : null;
    if (user != null) 
      return UserModel.User(uid: user.uid);
     else 
      return null;
    
  

  //auth change user stream
  Stream<UserModel.User?> get user 
    return _auth.authStateChanges()
        // .map((User? user) => _userFromFirebaseUser(user));
      .map(_userFromFirebaseUser);
  

  //Sign in anonymously
  Future signInAnon() async 
    try 
      UserCredential result = await _auth.signInAnonymously();
      User? user = result.user;
      return _userFromFirebaseUser(user);
     catch(e) 
      print(e.toString());
      return null;
    
  

  //Sign in with email and pass
  Future signInWithEmailAndPassword(String email, String password) async 
    try 
      UserCredential result = await _auth.signInWithEmailAndPassword(email: email, password: password);
      User? user = result.user;
      return _userFromFirebaseUser(user);
     catch(e) 
      print(e.toString());
      return null;
    
  

  //register with email and password
  Future registerWithEmailAndPassword(String email, String password) async 
    try 
      UserCredential result = await _auth.createUserWithEmailAndPassword(email: email, password: password);
      User? user = result.user;
      return _userFromFirebaseUser(user);
     catch(e) 
      print(e.toString());
      return null;
    
  

  //sign out
  Future signOut() async 
    try 
      return await _auth.signOut();
     catch(e) 
      print(e.toString());
      return null;
    
  

但是，我现在想在用户在聊天屏幕上发送聊天时使用当前的 Firebase UID 将其写入实时数据库。我该怎么做？我在下面尝试过，但迷路了（请参阅 FloatingActionButton 的 OnPressed 事件）。

import 'package:firebase_database/firebase_database.dart';
import 'package:flutter/material.dart';
import 'package:app/services/auth.dart';
import 'package:app/models/user.dart';

class Chat extends StatelessWidget  
  Chat(Key? key) : super(key: key);
  final database = FirebaseDatabase.instance.reference();

  @override
  Widget build(BuildContext context) 
    final groupChatRef = database.child('GroupID');

    return Scaffold(
      appBar: AppBar(
        title: Text('Group Chat Screen'),
        // actions: [
        //   TextButton.icon(
        //       onPressed: 
        //         Navigator.pop(context);
        //       ,
        //       icon: icon,
        //       label: label
        //   )
        // ],
      ),
      body: Align(
        alignment: Alignment.bottomLeft,
        child: Row(
          children: [
            Expanded(
              child: TextField(
                  decoration: InputDecoration(
                    hintText: "Write message...",
                  )
              ),
            ),
            FloatingActionButton(
              onPressed: () 
                var uid;
                final user = User(uid: uid);
                final myAuth = AuthService();
                print('MyAuth.user:');
                //This is where I get lost...
              ,
              child: Icon(Icons.send,color: Colors.white,size: 18,),
              backgroundColor: Colors.blue,
              elevation: 0,
            )
          ],
        ),
      )
    );
  

【参考方案1】：

您可以通过在auth服务中添加getter来获取用户uid

class AuthService 
  ...
  User? get currentUser => _auth.currentUser;
  ...

然后在您的浮动操作按钮中获取该用户并使用它的 uid

此外，使用依赖注入并在每次需要时停止创建实例会更好。

              onPressed: () 
                final String uid = authService.currentUser!.uid;
                // do other things
              ,

【讨论】：

谢谢！依赖注入的东西是什么意思？我在我的代码中哪里创建了太多实例？

@whatwhatwhat 您在 onPressed 函数中创建了一个 'AuthService' 的实例，您可以一次创建一个 AuthService 的实例，并在您需要的每个地方使用它。您可以使用Provider 之类的包将依赖项注入BuildContext 或使用GetIt 之类的包将它们注入内存本身。然后你可以得到这样的实例 context.read<AuthService>() 或使用 GetIt GetIt.I.get<AuthService>() 并使用它。