Dart/Flutter & Firebase RTDB -如何访问从RTDB检索到的嵌套地图

import 'package:flutter/material.dart';
import 'package:firebase_core/firebase_core.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) {
    DatabaseReference databaseRef = FirebaseDatabase.instance.reference();
    DatabaseReference usersRef = databaseRef.child("users");

    usersRef.onValue.listen((event) {
      DataSnapshot snapshot = event.snapshot;
      Map<dynamic, dynamic> usersMap = snapshot.value;
      
      // 访问嵌套地图数据
      if (usersMap != null) {
        usersMap.forEach((key, value) {
          print("User ID: $key");
          print("Name: ${value['name']}");
          print("Email: ${value['email']}");
        });
      }
    });

    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Firebase RTDB Example'),
        ),
        body: Center(
          child: Text('Check console for RTDB data'),
        ),
      ),
    );
  }
}