Flutter count App with setState, StatefulWidget

count_base_sample.dart

import 'package:flutter/material.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 Counter extends StatefulWidget {
  Counter({Key key}) : super(key: key);

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

class _CounterState extends State<Counter> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  void _decrementCounter() {
    setState(() {
      _counter--;
    });
  }

  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:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.display1,
            ),
          ],
        ),
      ),
      floatingActionButton: Column(
        mainAxisAlignment: MainAxisAlignment.end,
        
        children: <Widget>[
          _fab(Icon(Icons.exposure_plus_1), _incrementCounter),
          _fab(Icon(Icons.exposure_neg_1), _decrementCounter),
        ],
      ),
    );
  }
}