go_router_redirect.dart

// Copyright 2013 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.

// Copied from
// https://github.com/flutter/packages/blob/main/packages/go_router/example/lib/redirection.dart
// https://github.com/flutter/packages/blob/main/packages/go_router/example/lib/shared/data.dart

import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:go_router/go_router.dart';

void main() => runApp(App());

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

  final LoginInfo _loginInfo = LoginInfo();

  static const String title = 'GoRouter Example: Redirection';

  // add the login info into the tree as app state that can change over time
  @override
  Widget build(BuildContext context) {
    return MaterialApp.router(
      routeInformationProvider: _router.routeInformationProvider,
      routeInformationParser: _router.routeInformationParser,
      routerDelegate: _router.routerDelegate,
      title: title,
      debugShowCheckedModeBanner: false,
    );
  }

  late final GoRouter _router = GoRouter(
    routes: <GoRoute>[
      GoRoute(
        path: '/',
        builder: (BuildContext context, GoRouterState state) {
          return HomeScreen(loginInfo: _loginInfo, families: Families.data);
        },
        routes: <GoRoute>[
          GoRoute(
            path: 'family/:fid',
            builder: (BuildContext context, GoRouterState state) {
              return FamilyScreen(
                family: Families.family(state.params['fid']!),
              );
            },
            routes: <GoRoute>[
              GoRoute(
                path: 'person/:pid',
                builder: (BuildContext context, GoRouterState state) {
                  final Family family = Families.family(state.params['fid']!);
                  final Person person = family.person(state.params['pid']!);
                  return PersonScreen(family: family, person: person);
                },
              ),
            ],
          ),
        ],
      ),
      GoRoute(
        path: '/login',
        builder: (BuildContext context, GoRouterState state) {
          return LoginScreen(loginInfo: _loginInfo);
        },
      ),
    ],

    // redirect to the login page if the user is not logged in
    redirect: (GoRouterState state) {
      final bool loggedIn = _loginInfo.loggedIn;
      final bool loggingIn = state.subloc == '/login';
      if (!loggedIn) {
        return loggingIn ? null : '/login';
      }

      // if the user is logged in but still on the login page, send them to
      // the home page
      if (loggingIn) {
        return '/';
      }

      // no need to redirect at all
      return null;
    },

    // changes on the listenable will cause the router to refresh it's route
    refreshListenable: _loginInfo,
  );
}

class LoginScreen extends StatelessWidget {
  LoginScreen({ required this.loginInfo, super.key });

  final LoginInfo loginInfo;

  @override
  Widget build(BuildContext context) => Scaffold(
        appBar: AppBar(title: const Text(App.title)),
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              ElevatedButton(
                onPressed: () {
                  // log a user in, letting all the listeners know
                  loginInfo.login('test-user');

                  // router will automatically redirect from /login to / using
                  // refreshListenable
                  //context.go('/');
                },
                child: const Text('Login'),
              ),
            ],
          ),
        ),
      );
}

/// The home screen that shows a list of families.
class HomeScreen extends StatelessWidget {
  HomeScreen({ required this.loginInfo, required this.families, super.key });

  final LoginInfo loginInfo;
  final List<Family> families;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text(App.title),
        actions: <Widget>[
          IconButton(
            onPressed: loginInfo.logout,
            tooltip: 'Logout: ${loginInfo.userName}',
            icon: const Icon(Icons.logout),
          )
        ],
      ),
      body: ListView(
        children: <Widget>[
          for (final Family f in families)
            ListTile(
              title: Text(f.name),
              onTap: () => context.go('/family/${f.id}'),
            )
        ],
      ),
    );
  }
}

/// The screen that shows a list of persons in a family.
class FamilyScreen extends StatelessWidget {
  /// Creates a [FamilyScreen].
  const FamilyScreen({required this.family, Key? key}) : super(key: key);

  /// The family to display.
  final Family family;

  @override
  Widget build(BuildContext context) => Scaffold(
        appBar: AppBar(title: Text(family.name)),
        body: ListView(
          children: <Widget>[
            for (final Person p in family.people)
              ListTile(
                title: Text(p.name),
                onTap: () => context.go('/family/${family.id}/person/${p.id}'),
              ),
          ],
        ),
      );
}

/// The person screen.
class PersonScreen extends StatelessWidget {
  /// Creates a [PersonScreen].
  const PersonScreen({required this.family, required this.person, Key? key})
      : super(key: key);

  /// The family this person belong to.
  final Family family;

  /// The person to be displayed.
  final Person person;

  @override
  Widget build(BuildContext context) => Scaffold(
        appBar: AppBar(title: Text(person.name)),
        body: Text('${person.name} ${family.name} is ${person.age} years old'),
      );
}

class LoginInfo extends ChangeNotifier {
  String get userName => _userName;
  String _userName = '';

  bool get loggedIn => _userName.isNotEmpty;

  void login(String userName) {
    _userName = userName;
    notifyListeners();
  }

  void logout() {
    _userName = '';
    notifyListeners();
  }
}

/// Person data class.
class Person {
  /// Creates a [Person].
  Person({required this.id, required this.name, required this.age});

  /// The id of the person.
  final String id;

  /// The name of the person.
  final String name;

  /// The age of the person.
  final int age;
}

/// Family data class.
class Family {
  /// Creates a [Family].
  Family({required this.id, required this.name, required this.people});

  /// The id of the family.
  final String id;

  /// The name of the family.
  final String name;

  /// The list of [Person]s in the family.
  final List<Person> people;

  /// Gets the [Person] with the given id in this family.
  Person person(String pid) => people.singleWhere(
        (Person p) => p.id == pid,
        orElse: () => throw Exception('unknown person $pid for family $id'),
      );
}

/// The mock of families data.
class Families {
  Families._();

  /// The data.
  static final List<Family> data = <Family>[
    Family(
      id: 'f1',
      name: 'Sells',
      people: <Person>[
        Person(id: 'p1', name: 'Chris', age: 52),
        Person(id: 'p2', name: 'John', age: 27),
        Person(id: 'p3', name: 'Tom', age: 26),
      ],
    ),
    Family(
      id: 'f2',
      name: 'Addams',
      people: <Person>[
        Person(id: 'p1', name: 'Gomez', age: 55),
        Person(id: 'p2', name: 'Morticia', age: 50),
        Person(id: 'p3', name: 'Pugsley', age: 10),
        Person(id: 'p4', name: 'Wednesday', age: 17),
      ],
    ),
    Family(
      id: 'f3',
      name: 'Hunting',
      people: <Person>[
        Person(id: 'p1', name: 'Mom', age: 54),
        Person(id: 'p2', name: 'Dad', age: 55),
        Person(id: 'p3', name: 'Will', age: 20),
        Person(id: 'p4', name: 'Marky', age: 21),
        Person(id: 'p5', name: 'Ricky', age: 22),
        Person(id: 'p6', name: 'Danny', age: 23),
        Person(id: 'p7', name: 'Terry', age: 24),
        Person(id: 'p8', name: 'Mikey', age: 25),
        Person(id: 'p9', name: 'Davey', age: 26),
        Person(id: 'p10', name: 'Timmy', age: 27),
        Person(id: 'p11', name: 'Tommy', age: 28),
        Person(id: 'p12', name: 'Joey', age: 29),
        Person(id: 'p13', name: 'Robby', age: 30),
        Person(id: 'p14', name: 'Johnny', age: 31),
        Person(id: 'p15', name: 'Brian', age: 32),
      ],
    ),
  ];

  /// Looks up a family in the data.
  static Family family(String fid) {
    return data.singleWhere(
      (Family f) => f.id == fid,
      orElse: () => throw Exception('unknown family $fid'),
    );
  }
}

/// The relation of a person in a family.
class FamilyPerson {
  /// Creates a [FamilyPerson].
  FamilyPerson({required this.family, required this.person});

  /// The family.
  final Family family;

  /// the person.
  final Person person;
}