flutter/examples/api/lib/material/navigation_drawer/navigation_drawer.0.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.

// Builds an adaptive navigation widget layout. When the screen width is less than
// 450, A [NavigationBar] will be displayed. Otherwise, a [NavigationRail] will be
// displayed on the left side, and also a button to open the [NavigationDrawer].
// All of these navigation widgets are built from an identical list of data.

import 'package:flutter/material.dart';

/// Flutter code sample for [NavigationDrawer].

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

class ExampleDestination {
  const ExampleDestination(this.label, this.icon, this.selectedIcon);

  final String label;
  final Widget icon;
  final Widget selectedIcon;
}

const List<ExampleDestination> destinations = <ExampleDestination>[
  ExampleDestination('Messages', Icon(Icons.widgets_outlined), Icon(Icons.widgets)),
  ExampleDestination('Profile', Icon(Icons.format_paint_outlined), Icon(Icons.format_paint)),
  ExampleDestination('Settings', Icon(Icons.settings_outlined), Icon(Icons.settings)),
];

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      theme: ThemeData(useMaterial3: true),
      home: const NavigationDrawerExample(),
    );
  }
}

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

  @override
  State<NavigationDrawerExample> createState() => _NavigationDrawerExampleState();
}

class _NavigationDrawerExampleState extends State<NavigationDrawerExample> {
  final GlobalKey<ScaffoldState> scaffoldKey = GlobalKey<ScaffoldState>();

  int screenIndex = 0;
  late bool showNavigationDrawer;

  void handleScreenChanged(int selectedScreen) {
    setState(() {
      screenIndex = selectedScreen;
    });
  }

  void openDrawer() {
    scaffoldKey.currentState!.openEndDrawer();
  }

  Widget buildBottomBarScaffold() {
    return Scaffold(
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.spaceEvenly,
          children: <Widget>[
            Text('Page Index = $screenIndex'),
          ],
        ),
      ),
      bottomNavigationBar: NavigationBar(
        selectedIndex: screenIndex,
        onDestinationSelected: (int index) {
          setState(() {
            screenIndex = index;
          });
        },
        destinations: destinations.map(
          (ExampleDestination destination) {
            return NavigationDestination(
              label: destination.label,
              icon: destination.icon,
              selectedIcon: destination.selectedIcon,
              tooltip: destination.label,
            );
          },
        ).toList(),
      ),
    );
  }

  Widget buildDrawerScaffold(BuildContext context) {
    return Scaffold(
      key: scaffoldKey,
      body: SafeArea(
        bottom: false,
        top: false,
        child: Row(
          children: <Widget>[
            Padding(
              padding: const EdgeInsets.symmetric(horizontal: 5),
              child: NavigationRail(
                minWidth: 50,
                destinations: destinations.map(
                  (ExampleDestination destination) {
                    return NavigationRailDestination(
                      label: Text(destination.label),
                      icon: destination.icon,
                      selectedIcon: destination.selectedIcon,
                    );
                  },
                ).toList(),
                selectedIndex: screenIndex,
                useIndicator: true,
                onDestinationSelected: (int index) {
                  setState(() {
                    screenIndex = index;
                  });
                },
              ),
            ),
            const VerticalDivider(thickness: 1, width: 1),
            Expanded(
              child: Column(
                mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                children: <Widget>[
                  Text('Page Index = $screenIndex'),
                  ElevatedButton(
                    onPressed: openDrawer,
                    child: const Text('Open Drawer'),
                  ),
                ],
              ),
            ),
          ],
        ),
      ),
      endDrawer: NavigationDrawer(
        onDestinationSelected: handleScreenChanged,
        selectedIndex: screenIndex,
        children: <Widget>[
          Padding(
            padding: const EdgeInsets.fromLTRB(28, 16, 16, 10),
            child: Text(
              'Header',
              style: Theme.of(context).textTheme.titleSmall,
            ),
          ),
          ...destinations.map(
            (ExampleDestination destination) {
              return NavigationDrawerDestination(
                label: Text(destination.label),
                icon: destination.icon,
                selectedIcon: destination.selectedIcon,
              );
            },
          ),
          const Padding(
            padding: EdgeInsets.fromLTRB(28, 16, 28, 10),
            child: Divider(),
          ),
        ],
      ),
    );
  }

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    showNavigationDrawer = MediaQuery.of(context).size.width >= 450;
  }

  @override
  Widget build(BuildContext context) {
    return showNavigationDrawer ? buildDrawerScaffold(context) : buildBottomBarScaffold();
  }
}