Flutter count App with Provider

count_provider.dart

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

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter State Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: Counter(),
    );
  }
}

class CounterModel with ChangeNotifier {
  int _count = 0;
  int get count => _count;

  void increment() {
    _count++;
    notifyListeners();
  }

  void decrement() {
    _count--;
    notifyListeners();
  }
}

class Counter extends StatelessWidget {
  Counter({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return ChangeNotifierProvider(
      builder: (context) => CounterModel(),
      child: CounterUI()
    );
  }
}

class CounterUI extends StatelessWidget {
  Widget _fab(Icon icon, Function action) {
    return FloatingActionButton(
      child: icon,
      onPressed: action,
    );
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Count Sample State Management'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'You have pushed the button this many times:',
            ),
            Consumer<CounterModel>(
              builder: (context, counter, child) => Text(
                '${counter.count}',
                style: Theme.of(context).textTheme.display1,
              ),
            ),
          ],
        ),
      ),
      floatingActionButton: Column(
        mainAxisAlignment: MainAxisAlignment.end,
        children: <Widget>[
          _fab(Icon(Icons.exposure_plus_1),
              Provider.of<CounterModel>(context).increment),
          _fab(Icon(Icons.exposure_neg_1),
              Provider.of<CounterModel>(context).decrement),
        ],
      ),
    );
  }
}