ScopedModel counter app

main.dart

import 'dart:async';

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

void main() {
  // The app state.
  final myModel = CounterModel(42);

  // A timer, to simulate updates coming from outside the app.
  Timer.periodic(const Duration(seconds: 2), (_) => myModel.increment());

  // Provide the model to the top-most widget.
  runApp(MyApp(myModel));
}

class CounterModel extends Model {
  // The state variable.
  int counter;

  // The constructor, which takes the initial state.
  CounterModel(this.counter);

  // The method to mutate the state.
  void increment() {
    counter += 1;
    notifyListeners();
  }
}

class MyApp extends StatelessWidget {
  final CounterModel counterModel;

  MyApp(this.counterModel, {Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return ScopedModel(
      model: counterModel,
      child: MaterialApp(
        title: 'Flutter Demo',
        theme: ThemeData(
          primarySwatch: Colors.blue,
        ),
        home: MyHomePage(title: 'Flutter Demo Home Page'),
      ),
    );
  }
}

class MyHomePage extends StatefulWidget {
  final String title;

  MyHomePage({Key key, this.title}) : super(key: key);

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    final model = ScopedModel.of<CounterModel>(context, rebuildOnChange: true);

    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '${model.counter}',
              style: Theme.of(context).textTheme.display1,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () => model.increment(),
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }
}