import 'package:flutter/material.dart';

const Color darkBlue = Color.fromARGB(255, 18, 32, 47);

enum _Page {
  home,
  two,
  three,
}

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

class _MyApp extends StatefulWidget {
  const _MyApp();
  
  @override
  State<_MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<_MyApp> {
  final List<_Page> _pages = <_Page>[_Page.home];

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Navigator(
        onPopPage: (Route<void> route, void result) {
          if (!route.didPop(null)) {
            return false;
          }
          setState(() {
            _pages.removeLast();
          });
          return true;
        },
        pages: _pages.map((_Page page) {
          switch (page) {
            case _Page.home:
              return MaterialPage(
                child: Scaffold(
                  backgroundColor: darkBlue,
                  body: Center(
                    child: Column(
                      mainAxisAlignment: MainAxisAlignment.center,
                      children: <Widget>[
                        const Text('Home'),
                        TextButton(
                          onPressed: () {
                            setState(() {
                              _pages.add(_Page.two);
                            });
                          },
                          child: const Text('Go to PopScope page'),
                        ),
                        TextButton(
                          onPressed: () {
                            setState(() {
                              _pages.add(_Page.three);
                            });
                          },
                          child: const Text('Go to WillPopScope page'),
                        ),
                      ],
                    ),
                  ),
                ),
              );
            case _Page.two:
              return MaterialPage(
                child: _MyPopScopePage(),
              );
            case _Page.three:
              return MaterialPage(
                child: _MyWillPopScopePage(),
              );
          }
        }).toList(),
      ),
    );
  }
}

class _MyPopScopePage extends StatefulWidget {
  @override
  State<_MyPopScopePage> createState() => _MyPopScopePageState();
}

class _MyPopScopePageState extends State<_MyPopScopePage> {
  var canPop = true;

  @override
  Widget build(BuildContext context) => PopScope(
    canPop: canPop,
    onPopInvoked: (didPop) {
      print('PopScope onPopInvoked called. didPop=$didPop');
    },
    child: Scaffold(
      body: Column(
        children: [
          const ListTile(title: Text('You Are Next')),
          ListTile(
            onTap: () => Navigator.maybePop(context),
            title: const Text('Go Back'),
          ),
          CheckboxListTile(
            value: canPop,
            onChanged: (value) => setState(() {
              canPop = value!;
            }),
            title: const Text('Toggle canPop'),
          ),
        ],
      ),
    ),
  );
}


class _MyWillPopScopePage extends StatefulWidget {
  @override
  State<_MyWillPopScopePage> createState() => _MyWillPopScopePageState();
}

class _MyWillPopScopePageState extends State<_MyWillPopScopePage> {
  var canPop = true;

  @override
  Widget build(BuildContext context) => WillPopScope(
    onWillPop: () async {
      print('WillPopScope onWillPop called.');
      return canPop;
    },
    child: Scaffold(
      body: Column(
        children: [
          const ListTile(title: Text('You Are Next - WillPopScope page')),
          ListTile(
            onTap: () => Navigator.maybePop(context),
            title: const Text('Go Back'),
          ),
          CheckboxListTile(
            value: canPop,
            onChanged: (value) => setState(() {
              canPop = value!;
            }),
            title: const Text('Toggle canPop'),
          ),
        ],
      ),
    ),
  );
}