Demo of FirebaseDatabase orderByChild with Flutter

flutter-firebase-order-by-child.dart

import 'package:flutter/material.dart';
import 'package:firebase_database/firebase_database.dart';
import 'package:flutter/foundation.dart';

void main() => runApp(new MyApp());

class MyApp extends StatelessWidget {
  const subpath = 'flutter-firebase-order-by-child';

  MyApp() {
    demo();
  }

  void demo() async {
    await FirebaseDatabase.instance.reference().child(subpath).set({
      'Albert Einstein': {
        'year': 1879,
      },
      'Marie Curie': {
        'year': 1867,
      },
      'Nikola Tesla': {
        'year': 1856,
      },
      'William Shakespeare': {
        'year': 1564,
      },
    });

    debugPrint('Sorted years:');

    (await FirebaseDatabase.instance
            .reference()
            .child(subpath)
            .orderByChild('year')
            .limitToFirst(3)
            .onValue
            .first)
        .snapshot
        .value
        .values
        .forEach((v) => debugPrint(v['year'].toString()));
  }

  @override
  Widget build(BuildContext context) {
    return Center(child: Text('It works!', textDirection: TextDirection.ltr));
  }
}