flutter/examples/api/lib/widgets/navigator/navigator.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.

// Flutter code sample for Navigator

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Code Sample for Navigator',
      // MaterialApp contains our top-level Navigator
      initialRoute: '/',
      routes: <String, WidgetBuilder>{
        '/': (BuildContext context) => const HomePage(),
        '/signup': (BuildContext context) => const SignUpPage(),
      },
    );
  }
}

class HomePage extends StatelessWidget {
  const HomePage({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return DefaultTextStyle(
      style: Theme.of(context).textTheme.headline4!,
      child: Container(
        color: Colors.white,
        alignment: Alignment.center,
        child: const Text('Home Page'),
      ),
    );
  }
}

class CollectPersonalInfoPage extends StatelessWidget {
  const CollectPersonalInfoPage({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return DefaultTextStyle(
      style: Theme.of(context).textTheme.headline4!,
      child: GestureDetector(
        onTap: () {
          // This moves from the personal info page to the credentials page,
          // replacing this page with that one.
          Navigator.of(context)
              .pushReplacementNamed('signup/choose_credentials');
        },
        child: Container(
          color: Colors.lightBlue,
          alignment: Alignment.center,
          child: const Text('Collect Personal Info Page'),
        ),
      ),
    );
  }
}

class ChooseCredentialsPage extends StatelessWidget {
  const ChooseCredentialsPage({
    Key? key,
    required this.onSignupComplete,
  }) : super(key: key);

  final VoidCallback onSignupComplete;

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      onTap: onSignupComplete,
      child: DefaultTextStyle(
        style: Theme.of(context).textTheme.headline4!,
        child: Container(
          color: Colors.pinkAccent,
          alignment: Alignment.center,
          child: const Text('Choose Credentials Page'),
        ),
      ),
    );
  }
}

class SignUpPage extends StatelessWidget {
  const SignUpPage({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    // SignUpPage builds its own Navigator which ends up being a nested
    // Navigator in our app.
    return Navigator(
      initialRoute: 'signup/personal_info',
      onGenerateRoute: (RouteSettings settings) {
        WidgetBuilder builder;
        switch (settings.name) {
          case 'signup/personal_info':
            // Assume CollectPersonalInfoPage collects personal info and then
            // navigates to 'signup/choose_credentials'.
            builder = (BuildContext context) => const CollectPersonalInfoPage();
            break;
          case 'signup/choose_credentials':
            // Assume ChooseCredentialsPage collects new credentials and then
            // invokes 'onSignupComplete()'.
            builder = (BuildContext _) => ChooseCredentialsPage(
                  onSignupComplete: () {
                    // Referencing Navigator.of(context) from here refers to the
                    // top level Navigator because SignUpPage is above the
                    // nested Navigator that it created. Therefore, this pop()
                    // will pop the entire "sign up" journey and return to the
                    // "/" route, AKA HomePage.
                    Navigator.of(context).pop();
                  },
                );
            break;
          default:
            throw Exception('Invalid route: ${settings.name}');
        }
        return MaterialPageRoute<void>(builder: builder, settings: settings);
      },
    );
  }
}