flutter/examples/api/lib/material/dropdown_menu/dropdown_menu.1.dart

// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'package:collection/collection.dart';
import 'package:flutter/material.dart';

/// Flutter code sample for [DropdownMenu].

const List<String> list = <String>['One', 'Two', 'Three', 'Four'];

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

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData(useMaterial3: true),
      home: Scaffold(
        appBar: AppBar(title: const Text('DropdownMenu Sample')),
        body: const Center(child: DropdownMenuExample()),
      ),
    );
  }
}

class DropdownMenuExample extends StatefulWidget {
  const DropdownMenuExample({super.key});

  @override
  State<DropdownMenuExample> createState() => _DropdownMenuExampleState();
}

typedef MenuEntry = DropdownMenuEntry<String>;

class _DropdownMenuExampleState extends State<DropdownMenuExample> {
  static final List<MenuEntry> menuEntries = UnmodifiableListView<MenuEntry>(
    list.map<MenuEntry>((String name) => MenuEntry(value: name, label: name)),
  );
  String dropdownValue = list.first;

  @override
  Widget build(BuildContext context) {
    return DropdownMenu<String>(
      initialSelection: list.first,
      onSelected: (String? value) {
        // This is called when the user selects an item.
        setState(() {
          dropdownValue = value!;
        });
      },
      dropdownMenuEntries: menuEntries,
    );
  }
}