Drawer navigation in Flutter

main.dart

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

void main() {
  runApp(MaterialApp(
    home: RootPage(),
  ));
}

class Destination {
  final String name;
  final String routeName;
  final IconData iconData;
  Destination(this.name, this.routeName, this.iconData);
}

final List<Destination> destinations = [
  Destination('Home', '/', Icons.dashboard),
  Destination('Metrics', '/metrics', Icons.show_chart),
  Destination('Settings', '/settings', Icons.settings),
];

GlobalKey _navigatorKey = GlobalKey();

class RootPage extends StatefulWidget {
  @override
  _RootPageState createState() => _RootPageState();
}

class _RootPageState extends State<RootPage> {
  Destination destination = destinations.first;
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(),
      drawer: Drawer(
        child: Column(
          children: [
            DrawerHeader(
              child: Center(
                child: Text(
                  'MyApp',
                  style: Theme.of(context).textTheme.headline,
                ),
              ),
            ),
            ...destinations.map((d) {
              return ListTile(
                title: Text(d.name),
                leading: Icon(d.iconData),
                selected: d == destination,
                onTap: () => _changePage(d),
              );
            }),
          ],
        ),
      ),
      body: Navigator(
        key: _navigatorKey,
        onGenerateRoute: (settings) {
          var destination =
              destinations.firstWhere((d) => d.routeName == settings.name);
          return PageRouteBuilder(
              pageBuilder: (context, animation, secondaryAnimation) {
            return PageHost(destination);
          }, transitionsBuilder:
                  (context, animation, secondaryAnimation, child) {
            var curveTween = CurveTween(curve: Curves.easeInQuart);
            return FadeTransition(
              opacity: animation.drive(curveTween),
              child: child,
            );
          });
        },
      ),
    );
  }

  void _changePage(Destination d) {
    var navState = _navigatorKey.currentState as NavigatorState;
    navState.pushNamed(d.routeName);
    setState(() {
      destination = d;
    });
    Navigator.of(context).pop();
  }
}

class PageHost extends StatelessWidget {
  final Destination destination;

  PageHost(this.destination);

  @override
  Widget build(BuildContext context) {
    return Container(
      child: Center(
        child: Text(destination.name, style: Theme.of(context).textTheme.display3,),
      ),
    );
  }
}