有没有办法在flutter应用程序中使用firebase来查找具有相同孩子名称的孩子的总和？

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) {
    return MaterialApp(
      title: 'Firebase Demo',
      home: MyHomePage(),
    );
  }
}

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

class _MyHomePageState extends State<MyHomePage> {
  DatabaseReference _databaseRef;

  @override
  void initState() {
    super.initState();
    _databaseRef = FirebaseDatabase.instance.reference();
  }

  Future<int> getChildSum(String childName) async {
    int sum = 0;
    DataSnapshot snapshot = await _databaseRef
        .orderByChild('childName')
        .equalTo(childName)
        .once();

    if (snapshot.value != null) {
      Map<dynamic, dynamic> values = snapshot.value;
      values.forEach((key, data) {
        sum += data['value'];
      });
    }

    return sum;
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Firebase Demo'),
      ),
      body: Center(
        child: RaisedButton(
          child: Text('Get Child Sum'),
          onPressed: () async {
            int sum = await getChildSum('childName');
            print('Sum: $sum');
          },
        ),
      ),
    );
  }
}