packages/go_router/example/lib/others/nav_observer.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.

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

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

/// The main app.
class App extends StatelessWidget {
  /// Creates an [App].
  App({super.key});

  /// The title of the app.
  static const String title = 'GoRouter Example: Navigator Observer';

  @override
  Widget build(BuildContext context) => MaterialApp.router(
        routerConfig: _router,
        title: title,
      );

  final GoRouter _router = GoRouter(
    observers: <NavigatorObserver>[MyNavObserver()],
    routes: <GoRoute>[
      GoRoute(
        // if there's no name, path will be used as name for observers
        path: '/',
        builder: (BuildContext context, GoRouterState state) =>
            const Page1Screen(),
        routes: <GoRoute>[
          GoRoute(
            name: 'page2',
            path: 'page2/:p1',
            builder: (BuildContext context, GoRouterState state) =>
                const Page2Screen(),
            routes: <GoRoute>[
              GoRoute(
                name: 'page3',
                path: 'page3',
                builder: (BuildContext context, GoRouterState state) =>
                    const Page3Screen(),
              ),
            ],
          ),
        ],
      ),
    ],
  );
}

/// The Navigator observer.
class MyNavObserver extends NavigatorObserver {
  /// Creates a [MyNavObserver].
  MyNavObserver() {
    log.onRecord.listen((LogRecord e) => debugPrint('$e'));
  }

  /// The logged message.
  final Logger log = Logger('MyNavObserver');

  @override
  void didPush(Route<dynamic> route, Route<dynamic>? previousRoute) =>
      log.info('didPush: ${route.str}, previousRoute= ${previousRoute?.str}');

  @override
  void didPop(Route<dynamic> route, Route<dynamic>? previousRoute) =>
      log.info('didPop: ${route.str}, previousRoute= ${previousRoute?.str}');

  @override
  void didRemove(Route<dynamic> route, Route<dynamic>? previousRoute) =>
      log.info('didRemove: ${route.str}, previousRoute= ${previousRoute?.str}');

  @override
  void didReplace({Route<dynamic>? newRoute, Route<dynamic>? oldRoute}) =>
      log.info('didReplace: new= ${newRoute?.str}, old= ${oldRoute?.str}');

  @override
  void didStartUserGesture(
    Route<dynamic> route,
    Route<dynamic>? previousRoute,
  ) =>
      log.info('didStartUserGesture: ${route.str}, '
          'previousRoute= ${previousRoute?.str}');

  @override
  void didStopUserGesture() => log.info('didStopUserGesture');
}

extension on Route<dynamic> {
  String get str => 'route(${settings.name}: ${settings.arguments})';
}

/// The screen of the first page.
class Page1Screen extends StatelessWidget {
  /// Creates a [Page1Screen].
  const Page1Screen({super.key});

  @override
  Widget build(BuildContext context) => Scaffold(
        appBar: AppBar(title: const Text(App.title)),
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              ElevatedButton(
                onPressed: () => context.goNamed(
                  'page2',
                  pathParameters: <String, String>{'p1': 'pv1'},
                  queryParameters: <String, String>{'q1': 'qv1'},
                ),
                child: const Text('Go to page 2'),
              ),
            ],
          ),
        ),
      );
}

/// The screen of the second page.
class Page2Screen extends StatelessWidget {
  /// Creates a [Page2Screen].
  const Page2Screen({super.key});

  @override
  Widget build(BuildContext context) => Scaffold(
        appBar: AppBar(title: const Text(App.title)),
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              ElevatedButton(
                onPressed: () => context.goNamed(
                  'page3',
                  pathParameters: <String, String>{'p1': 'pv2'},
                ),
                child: const Text('Go to page 3'),
              ),
            ],
          ),
        ),
      );
}

/// The screen of the third page.
class Page3Screen extends StatelessWidget {
  /// Creates a [Page3Screen].
  const Page3Screen({super.key});

  @override
  Widget build(BuildContext context) => Scaffold(
        appBar: AppBar(title: const Text(App.title)),
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              ElevatedButton(
                onPressed: () => context.go('/'),
                child: const Text('Go to home page'),
              ),
            ],
          ),
        ),
      );
}