flutter_riverpod: ^1.0.2

flutter_riverpod_example.dart

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

void main() => runApp(ProviderScope(child: Sys()));

class Sys extends StatelessWidget {
  const Sys({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) => MaterialApp(home: Main());
}

class Main extends StatelessWidget {
  const Main({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return HomeView();
  }
}

class HomeView extends StatelessWidget {
  const HomeView({Key? key,}) : super(key: key);

  @override
  Widget build(BuildContext context) => MainPage();
}

class Logic extends StateNotifier<List<String>>{

  Logic([List<String>? datas]) : super( datas ?? []);

  void add(String data) => state = [...state, data];
}
StateNotifierProvider<Logic, List<String>> provider = StateNotifierProvider<Logic, List<String>>((ref) => Logic());

class MainPage extends ConsumerWidget{
  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final List<String> _datas = ref.watch(provider);
    final Logic _logic = ref.read<Logic>(provider.notifier);
    return Scaffold(
      appBar: AppBar(
        actions: [
          IconButton(
            icon: Icon(Icons.watch),
            onPressed: () => Navigator.of(context).push(
              MaterialPageRoute(builder: (_) => Sub())
            ),
          )
        ],
      ),
      body: ListView.builder(
        itemCount: _datas.length,
        itemBuilder: (BuildContext context, int index) => ListTile(
          title: Text(_datas[index].toString()) // watch
        ),
      ),
      floatingActionButton: FloatingActionButton(
        child: Icon(Icons.add),
        onPressed: () => _logic.add('value'), // read
      ),
    );
  }
}

class Sub extends StatelessWidget {
  const Sub({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return SubPage();
  }
}


class SubPage extends ConsumerWidget{
  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final List<String> _datas = ref.watch<List<String>>(provider);
    final Logic _logic = ref.read<Logic>(provider.notifier);
    return Scaffold(
    appBar: AppBar(),
    body: Center(child: Text("watch : $_datas \n/ read : ${_logic.state}"),),
    floatingActionButton: FloatingActionButton(
      child: Icon(Icons.add_link),
      onPressed: () async{
        await showDialog(
          context: context,
          builder: (context) => AlertDialog(
            title: Text("read ref .addDATA"),
          )
        );
        _logic.add("data");
      },
    ),
  );
  }

}