PopScope.onPopInvokedBehaviour

main.dart

// Copyright (c) 2019, the Dart project authors.  Please see the AUTHORS file
// for details. 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';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
        useMaterial3: true,
      ),
      home:  MyHomePage(),
    );
  }
}

class MyHomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('PopScope Example')),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            TextButton(
              onPressed: () => Navigator.of(context).push(MaterialPageRoute(builder: (context) => CanPopTrue())),
              child: const Text('Page with canPop true'),
            ),
            TextButton(
              onPressed: () => Navigator.of(context).push(MaterialPageRoute(builder: (context) => CanPopFalse())),
              child: const Text('Page with canPop false'),
            ),
            TextButton(
              onPressed: () => Navigator.of(context).push(MaterialPageRoute(builder: (context) => CanPopFalseButAllowedNotCatchingSecondaryCall())),
              child: const Text('Page with canPop false but allowed'),
            ),
            TextButton(
              onPressed: () => Navigator.of(context).push(MaterialPageRoute(builder: (context) => CanPopFalseButAllowedCatchingSecondaryCall())),
              child: const Text('Page with canPop false but allowed'),
            ),
          ],
        ),
      ),
    );
  }
}

class CanPopTrue extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return PopScope(
      canPop: true,
      onPopInvoked: (didPop) {
        print('$runtimeType didPop: $didPop');
      },
      child: Scaffold(
        appBar: AppBar(title: const Text('Can Pop True')),
        body: const Center(child: Text('Can Pop True')),
      ),
    );
  }
}

class CanPopFalse extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return PopScope(
      canPop: false,
      onPopInvoked: (didPop) {
        print('$runtimeType didPop: $didPop');
      },
      child: Scaffold(
        appBar: AppBar(title: const Text('Can Pop False')),
        body: const Center(child: Text('Can Pop False (re-run to go back)')),
      ),
    );
  }
}

class CanPopFalseButAllowedNotCatchingSecondaryCall extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return PopScope(
      canPop: false,
      onPopInvoked: (didPop) {
        print('$runtimeType didPop: $didPop');
        
        Navigator.of(context).pop();
      },
      child: Scaffold(
        appBar: AppBar(title: const Text('Can Pop False But Allowed')),
        body: const Center(child: Text('Can Pop False But Allowed but not catching the secondary call to onPopInvoked (re-run to go back)')),
      ),
    );
  }
}


class CanPopFalseButAllowedCatchingSecondaryCall extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return PopScope(
      canPop: false,
      onPopInvoked: (didPop) {
        print('$runtimeType didPop: $didPop');
        
        /// Unlike CanPopFalseButAllowedNotCatchingSecondaryCall, the 
        /// second time this callback is invoked we check if the pop
        /// was allowed and then just don't run any Navigation related
        /// functions.
        ///
        /// On Web the error in CanPopFalseButAllowedNotCatchingSecondaryCall
        /// doesn't come through very well but on iOS/Android it provides a
        /// bit more detail.
        if (didPop) {
          return;
        }
        
        Navigator.of(context).pop();
      },
      child: Scaffold(
        appBar: AppBar(title: const Text('Can Pop False But Allowed')),
        body: const Center(child: Text('Can Pop False But Allowed catching the secondary call to onPopInvoked')),
      ),
    );
  }
}