flutter_flutter/examples/api/lib/widgets/routes/route_observer.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.

import 'package:flutter/material.dart';

/// Flutter code sample for [RouteObserver].

final RouteObserver<ModalRoute<void>> routeObserver =
    RouteObserver<ModalRoute<void>>();

void main() {
  runApp(const RouteObserverApp());
}

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      navigatorObservers: <NavigatorObserver>[routeObserver],
      home: const RouteObserverExample(),
    );
  }
}

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

  @override
  State<RouteObserverExample> createState() => _RouteObserverExampleState();
}

class _RouteObserverExampleState extends State<RouteObserverExample>
    with RouteAware {
  List<String> log = <String>[];

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    routeObserver.subscribe(this, ModalRoute.of(context)!);
  }

  @override
  void dispose() {
    routeObserver.unsubscribe(this);
    super.dispose();
  }

  @override
  void didPush() {
    // Route was pushed onto navigator and is now the topmost route.
    log.add('didPush');
  }

  @override
  void didPopNext() {
    // Covering route was popped off the navigator.
    log.add('didPopNext');
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: SingleChildScrollView(
        child: Center(
          child: Column(
            mainAxisSize: MainAxisSize.min,
            children: <Widget>[
              Text(
                'RouteObserver log:',
                style: Theme.of(context).textTheme.headlineSmall,
              ),
              ConstrainedBox(
                constraints: const BoxConstraints(maxHeight: 300.0),
                child: ListView.builder(
                  itemCount: log.length,
                  itemBuilder: (BuildContext context, int index) {
                    if (log.isEmpty) {
                      return const SizedBox.shrink();
                    }
                    return Text(log[index], textAlign: TextAlign.center);
                  },
                ),
              ),
              OutlinedButton(
                onPressed: () {
                  Navigator.of(context).push<void>(
                    MaterialPageRoute<void>(
                      builder: (BuildContext context) => const NextPage(),
                    ),
                  );
                },
                child: const Text('Go to next page'),
              ),
            ],
          ),
        ),
      ),
    );
  }
}

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: FilledButton(
          onPressed: () {
            Navigator.of(context).pop();
          },
          child: const Text('Go back to RouteAware page'),
        ),
      ),
    );
  }
}