main.dart

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

final score_state = StateProvider<int>((ref) => 0);

main() {
    runApp(
        ProviderScope(child: MaterialApp.router(
            debugShowCheckedModeBanner: false,
            theme: ThemeData.dark(),
            routerConfig: GoRouter(routes: [
                GoRoute(
                    path: '/',
                    builder: (context, state) => Foo(),
                ),
                GoRoute(
                    path: '/bar',
                    builder: (context, state) => Bar()
                )
            ])
        ))
    );
}

class Foo extends ConsumerWidget {
    @override Widget build(BuildContext context, WidgetRef ref) {

        // FETCH SCORE STATE
        final score = ref.watch(score_state);

        return Column(children: [
            Text('$score'),
            ElevatedButton(
                onPressed: () => context.go('/bar'), 
                child: Text('GOTO UPDATER')
            )
        ]);
    }
}

class Bar extends ConsumerWidget {

    void foo(WidgetRef ref) {
        ref.watch(score_state.notifier).update((state) => state + 1);
    }

    @override Widget build(BuildContext context, WidgetRef ref) {

        return Column(children: [
            ElevatedButton(
                onPressed: () => foo(ref),
                child: Text('UPDATE')
            ),
            ElevatedButton(
                onPressed: () => context.go('/'), 
                child: Text('GOTO SUBSCRIBER')
            )
        ]);
    }
}