import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        body: DropdownMenu<int>(
          searchCallback: (List<DropdownMenuEntry<int>> entries, String query) {
            if (query.isEmpty) {
              return null;
            }
            final int index = entries.indexWhere(
              (DropdownMenuEntry<int> entry) => entry.label.contains(query),
            );

            return index != -1 ? index : null;
          },
          dropdownMenuEntries: const <DropdownMenuEntry<int>>[
            DropdownMenuEntry<int>(value: 0, label: 'ABC'),
            DropdownMenuEntry<int>(value: 1, label: 'AB'),
            DropdownMenuEntry<int>(value: 2, label: 'ABCD'),
          ],
        ),
      ),
    );
  }
}