Singletone services and provider

home.dart

import 'service.dart';

class HomeScreen extends StatelessWidget {
  @override
  build(BuildContext context) {
    // When service will notify its listeners, we'll be automatically
    // rebuilt
    List<Model> items = Provider.of<Service>(context).items;

    return Scaffold(
      body: Column(
        children: <Widget>[
          ...items.map((Model item) => Text(item.name)),
          Button(
            onPressed: () {
              // Dispatch action to service, no need to
              // use provider for this 
              Service.instance.fetchItems();
            } 
          )
        ]
      )
    );
  }
}

main.dart

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

class RootWidget extends StatefulWidget {
  @override
  _RootWidgetState createState() => _RootWidgetState();
}

class _RootWidgetState extends State<RootWidget> {
  Service service;

  Future init() async {
    service = Service.instance;
    
    return Future.wait(<Future>[
      service.init(),
    ]);
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Example app',
      routes: {
        '/': _buildRoot,
      },
    );
  }

  Widget _buildRoot(context) {
    return FutureBuilder(
      future: init(),
      builder: (BuildContext context, AsyncSnapshot snapshot) {
        if (snapshot.hasData) {
          return HomeScreen();
        } else if (snapshot.hasError) {
          return ErrorScreen();
        }

        return SplashScreen();
      },
    );
  }
}

model.dart

class Model {
  String name;
  Model({ this.name });
}

service.dart

class Service with ChangeNotifier {
  static final Service _instance = Service();
  static Service get instance => _instance;

  // Needs to be 
  // rendered in list
  List<Model> items = [];

  Future init() async {
    // Do something asynchronous, for example read SharedPreferences
    // or query sqflite db.
    return Future.delayed(const Duration(milliseconds: 1000));
  }

  Future fetchItems() async {
    List<Model> response = await api.get('/items');

    items.addAll(response);
    notifyListeners();
  }
}