{新的Flutter/Dart程序员}有什么简单的方法可以简单地访问Firebase数据库中的“字段”并将其值设置为变量吗？

import 'package:flutter/material.dart';
import 'package:firebase_core/firebase_core.dart';
import 'package:cloud_firestore/cloud_firestore.dart';

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

  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  final FirebaseFirestore firestore = FirebaseFirestore.instance;
  
  @override
  Widget build(BuildContext context) {
    CollectionReference users = firestore.collection('users');
    
    return FutureBuilder<DocumentSnapshot>(
      future: users.doc('your_document_id').get(),
      builder:
          (BuildContext context, AsyncSnapshot<DocumentSnapshot> snapshot) {
        if (snapshot.hasError) {
          return Text("Something went wrong");
        }

        if (snapshot.connectionState == ConnectionState.done) {
          Map<String, dynamic> data = snapshot.data!.data() as Map<String, dynamic>;
          String fieldValue = data['your_field'];

          return Text("Field value: $fieldValue");
        }

        return Text("Loading");
      },
    );
  }
}

import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'dart:convert';

void main() {
  runApp(MyApp());
}

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  String fieldValue = '';

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

  Future<void> fetchData() async {
    var url = Uri.parse('https://your-project.firebaseio.com/users/your_document_id.json');
    var response = await http.get(url);
    var data = json.decode(response.body);

    setState(() {
      fieldValue = data['your_field'];
    });
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        body: Center(
          child: Text('Field value: $fieldValue'),
        ),
      ),
    );
  }
}