Flutter Firebase查询-在文本小部件中显示设置值

import 'package:flutter/material.dart';
import 'package:firebase_core/firebase_core.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:firebase_database/firebase_database.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Firebase Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  final FirebaseAuth _auth = FirebaseAuth.instance;
  final DatabaseReference _database =
      FirebaseDatabase.instance.reference().child('settings');

  String _settingValue = '';

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

  void fetchData() async {
    User user = _auth.currentUser;
    if (user != null) {
      DataSnapshot snapshot = await _database.once();
      setState(() {
        _settingValue = snapshot.value['setting'];
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Flutter Firebase Demo'),
      ),
      body: Center(
        child: Text(
          'Setting Value: $_settingValue',
          style: TextStyle(fontSize: 24),
        ),
      ),
    );
  }
}