RouteObserverWithCancelableOperation

RouteObserverWithCancelableOperation.dart

import 'dart:async';

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

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

final RouteObserver<PageRoute> routeObserver = RouteObserver<PageRoute>();

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
        useMaterial3: true,
      ),
      home: const HomePage(),
      navigatorObservers: [routeObserver],
    );
  }
}

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

  @override
  State<HomePage> createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> with RouteAware {
  /// An asynchronous operation that can be cancelled.
  ///
  /// Executes [_handleSomething]
  CancelableOperation? _connectOperation;

  /// Called when the current route has been pushed, from [RouteAware].
  @override
  void didPush() {
    debugPrint('HomePage: Called didPush');
    super.didPush();
  }

  /// Called when the current route has been popped off, from [RouteAware].
  @override
  void didPop() {
    debugPrint('HomePage: Called didPop');
    super.didPop();
  }

  /// Called when the top route has been popped off, and the current route, from [RouteAware].
  /// shows up.
  ///
  /// You can check stats of [_connectOperation] when user navigates back to this screen.
  @override
  void didPopNext() {
    debugPrint("Ops status : ${_connectOperation?.isCanceled}");
    debugPrint("Ops status : ${_connectOperation?.isCompleted}");
    super.didPopNext();
  }

  /// Called when a new route has been pushed, and the current route is no
  /// longer visible.
  ///
  /// Cancel [_connectOperation] when user navigates to [SecondPage].
  @override
  void didPushNext() {
    if (_connectOperation != null && !_connectOperation!.isCompleted) {
      _connectOperation?.cancel(); // Cancel operation.
    }
    debugPrint('HomePage: Called didPushNext');
    super.didPushNext();
  }

  /// Run you tasks.
  ///
  /// Uses [Future.delayed] to delay the execution.
  /// You can use [Timer] or [Timer.periodic].
  Future<dynamic> _handleSomething() async {
    await Future.delayed(const Duration(minutes: 1));
    debugPrint('Running your work after 15 seconds  ....');
  }

  @override
  void initState() {
    super.initState();
    _connectOperation = CancelableOperation.fromFuture(_handleSomething());
  }

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

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Colors.cyan,
        automaticallyImplyLeading: false,
        title: const Text('Flutter RouteAware Demo'),
      ),
      body: Center(
        child: Padding(
          padding: const EdgeInsets.all(16.0),
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            crossAxisAlignment: CrossAxisAlignment.center,
            children: [
              SizedBox(
                height: MediaQuery.of(context).size.height * 0.25,
              ),
              ElevatedButton(
                  style: ElevatedButton.styleFrom(
                    textStyle: const TextStyle(fontSize: 20),
                    minimumSize: const Size.fromHeight(40),
                  ),
                  onPressed: () => Navigator.of(context).push(
                        MaterialPageRoute(
                          builder: (context) => const SecondPage(),
                        ),
                      ),
                  child: const Text(
                    "Home Page",
                  )),
            ],
          ),
        ),
      ),
    );
  }
}

class SecondPage extends StatefulWidget {
  const SecondPage({Key? key}) : super(key: key);

  @override
  State<SecondPage> createState() => _SecondPageState();
}

class _SecondPageState extends State<SecondPage> {
  @override
  void initState() {
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Colors.cyan,
        title: const Text('Second Page'),
      ),
      body: const Center(
        child: Text(
          "Flutter Dev's",
          style: TextStyle(fontSize: 35.0),
        ),
      ),
    );
  }
}