flutter/examples/flutter_gallery/lib/demo/material/menu_demo.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:flutter/material.dart';

import '../../gallery/demo.dart';

class MenuDemo extends StatefulWidget {
  const MenuDemo({ Key key }) : super(key: key);

  static const String routeName = '/material/menu';

  @override
  MenuDemoState createState() => MenuDemoState();
}

class MenuDemoState extends State<MenuDemo> {
  final GlobalKey<ScaffoldState> _scaffoldKey = GlobalKey<ScaffoldState>();

  final String _simpleValue1 = 'Menu item value one';
  final String _simpleValue2 = 'Menu item value two';
  final String _simpleValue3 = 'Menu item value three';
  String _simpleValue;

  final String _checkedValue1 = 'One';
  final String _checkedValue2 = 'Two';
  final String _checkedValue3 = 'Free';
  final String _checkedValue4 = 'Four';
  List<String> _checkedValues;

  @override
  void initState() {
    super.initState();
    _simpleValue = _simpleValue2;
    _checkedValues = <String>[_checkedValue3];
  }

  void showInSnackBar(String value) {
    _scaffoldKey.currentState.showSnackBar(SnackBar(
     content: Text(value),
    ));
  }

  void showMenuSelection(String value) {
    if (<String>[_simpleValue1, _simpleValue2, _simpleValue3].contains(value))
      _simpleValue = value;
    showInSnackBar('You selected: $value');
  }

  void showCheckedMenuSelections(String value) {
    if (_checkedValues.contains(value))
      _checkedValues.remove(value);
    else
      _checkedValues.add(value);

    showInSnackBar('Checked $_checkedValues');
  }

  bool isChecked(String value) => _checkedValues.contains(value);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      key: _scaffoldKey,
      appBar: AppBar(
        title: const Text('Menus'),
        actions: <Widget>[
          MaterialDemoDocumentationButton(MenuDemo.routeName),
          PopupMenuButton<String>(
            onSelected: showMenuSelection,
            itemBuilder: (BuildContext context) => <PopupMenuItem<String>>[
              const PopupMenuItem<String>(
                value: 'Toolbar menu',
                child: Text('Toolbar menu'),
              ),
              const PopupMenuItem<String>(
                value: 'Right here',
                child: Text('Right here'),
              ),
              const PopupMenuItem<String>(
                value: 'Hooray!',
                child: Text('Hooray!'),
              ),
            ],
          ),
        ],
      ),
      body: ListView(
        padding: kMaterialListPadding,
        children: <Widget>[
          // Pressing the PopupMenuButton on the right of this item shows
          // a simple menu with one disabled item. Typically the contents
          // of this "contextual menu" would reflect the app's state.
          ListTile(
            title: const Text('An item with a context menu button'),
            trailing: PopupMenuButton<String>(
              padding: EdgeInsets.zero,
              onSelected: showMenuSelection,
              itemBuilder: (BuildContext context) => <PopupMenuItem<String>>[
                PopupMenuItem<String>(
                  value: _simpleValue1,
                  child: const Text('Context menu item one'),
                ),
                const PopupMenuItem<String>(
                  enabled: false,
                  child: Text('A disabled menu item'),
                ),
                PopupMenuItem<String>(
                  value: _simpleValue3,
                  child: const Text('Context menu item three'),
                ),
              ],
            ),
          ),
          // Pressing the PopupMenuButton on the right of this item shows
          // a menu whose items have text labels and icons and a divider
          // That separates the first three items from the last one.
          ListTile(
            title: const Text('An item with a sectioned menu'),
            trailing: PopupMenuButton<String>(
              padding: EdgeInsets.zero,
              onSelected: showMenuSelection,
              itemBuilder: (BuildContext context) => <PopupMenuEntry<String>>[
                const PopupMenuItem<String>(
                  value: 'Preview',
                  child: ListTile(
                    leading: Icon(Icons.visibility),
                    title: Text('Preview'),
                  ),
                ),
                const PopupMenuItem<String>(
                  value: 'Share',
                  child: ListTile(
                    leading: Icon(Icons.person_add),
                    title: Text('Share'),
                  ),
                ),
                const PopupMenuItem<String>(
                  value: 'Get Link',
                  child: ListTile(
                    leading: Icon(Icons.link),
                    title: Text('Get link'),
                  ),
                ),
                const PopupMenuDivider(),
                const PopupMenuItem<String>(
                  value: 'Remove',
                  child: ListTile(
                    leading: Icon(Icons.delete),
                    title: Text('Remove'),
                  ),
                ),
              ],
            ),
          ),
          // This entire list item is a PopupMenuButton. Tapping anywhere shows
          // a menu whose current value is highlighted and aligned over the
          // list item's center line.
          PopupMenuButton<String>(
            padding: EdgeInsets.zero,
            initialValue: _simpleValue,
            onSelected: showMenuSelection,
            child: ListTile(
              title: const Text('An item with a simple menu'),
              subtitle: Text(_simpleValue),
            ),
            itemBuilder: (BuildContext context) => <PopupMenuItem<String>>[
              PopupMenuItem<String>(
                value: _simpleValue1,
                child: Text(_simpleValue1),
              ),
              PopupMenuItem<String>(
                value: _simpleValue2,
                child: Text(_simpleValue2),
              ),
              PopupMenuItem<String>(
                value: _simpleValue3,
                child: Text(_simpleValue3),
              ),
            ],
          ),
          // Pressing the PopupMenuButton on the right of this item shows a menu
          // whose items have checked icons that reflect this app's state.
          ListTile(
            title: const Text('An item with a checklist menu'),
            trailing: PopupMenuButton<String>(
              padding: EdgeInsets.zero,
              onSelected: showCheckedMenuSelections,
              itemBuilder: (BuildContext context) => <PopupMenuItem<String>>[
                CheckedPopupMenuItem<String>(
                  value: _checkedValue1,
                  checked: isChecked(_checkedValue1),
                  child: Text(_checkedValue1),
                ),
                CheckedPopupMenuItem<String>(
                  value: _checkedValue2,
                  enabled: false,
                  checked: isChecked(_checkedValue2),
                  child: Text(_checkedValue2),
                ),
                CheckedPopupMenuItem<String>(
                  value: _checkedValue3,
                  checked: isChecked(_checkedValue3),
                  child: Text(_checkedValue3),
                ),
                CheckedPopupMenuItem<String>(
                  value: _checkedValue4,
                  checked: isChecked(_checkedValue4),
                  child: Text(_checkedValue4),
                ),
              ],
            ),
          ),
        ],
      ),
    );
  }
}