您可以使用StateProvider<User?>存储当前用户。如果没有用户连接，则值为null。
下面是一个如何使用它的例子：

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

void main() {
  runApp(ProviderScope(child: const MyApp()));
}

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

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    return MaterialApp(
      home: Scaffold(
        body: SafeArea(
          child: Center(
            child: Column(
              children: <Widget>[
                Text('Hello ${ref.watch(currentUserProvider)?.name}'),
                ElevatedButton(
                  child: const Text('login'),
                  onPressed: () {
                    // Fake retrieve user from server, for instance:
                    // final User user = await ref.read(firestoreRepoProvider).getUser(uid: uid);
                    ref.read(currentUserProvider.notifier).state = User('John', 'uid');
                  },
                ),
                ElevatedButton(
                  child: const Text('logout'),
                  onPressed: () {
                    // Fake logout
                    ref.read(currentUserProvider.notifier).state = null;
                  },
                ),
              ],
            ),
          ),
        ),
      ),
    );
  }
}

final StateProvider<User?> currentUserProvider = StateProvider<User?>((_) => null);

class User {
  User(this.name, this.uid);
  final String name;
  final String uid;
}

我创建了一个currentUserProvider，可以在你的小部件中查看。我添加了两个按钮，假登录和注销，告诉你如何更新当前用户。