如何在React应用程序中处理Firebase onAuthStateChanged并相应地路由用户？

// firebase.js

import firebase from 'firebase/app';
import 'firebase/auth';

const firebaseConfig = {
  // Firebase配置信息
};

firebase.initializeApp(firebaseConfig);

export const auth = firebase.auth();
export const firebaseInstance = firebase;

// App.js

import React, { useEffect, useState } from 'react';
import { BrowserRouter as Router, Switch, Route, Redirect } from 'react-router-dom';
import { auth } from './firebase';

const App = () => {
  const [user, setUser] = useState(null);

  useEffect(() => {
    const unsubscribe = auth.onAuthStateChanged((user) => {
      setUser(user);
    });

    return () => unsubscribe();
  }, []);

  return (
    <Router>
      <Switch>
        <Route exact path="/">
          {user ? <Redirect to="/dashboard" /> : <Redirect to="/login" />}
        </Route>
        <Route path="/login" component={Login} />
        <Route path="/dashboard" component={Dashboard} />
      </Switch>
    </Router>
  );
};

export default App;

// Dashboard.js

import React, { useEffect } from 'react';
import { useHistory } from 'react-router-dom';
import { auth } from './firebase';

const Dashboard = () => {
  const history = useHistory();

  useEffect(() => {
    if (!auth.currentUser) {
      history.push('/login');
    }
  }, [history]);

  return (
    <div>
      <h1>Dashboard</h1>
      {/* Dashboard内容 */}
    </div>
  );
};

export default Dashboard;