20 Flutter: IconButton

main.dart

import 'package:flutter/material.dart';

void main(){
  runApp(new MaterialApp(
    home: new MyApp(),
  ));
}

class MyApp extends StatefulWidget {
  @override
  _State createState() => new _State();
}

//State is information of the application that can change over time or when some actions are taken.
class _State extends State<MyApp>{

  int _value = 0;

  void _add() {
    setState(() {
      _value++;
    });
  }

  void _subtract() {
    setState(() {
      _value--;
    });
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text('Name here'),
      ),
      //hit Ctrl+space in intellij to know what are the options you can use in flutter widgets
      body: new Container(
        padding: new EdgeInsets.all(32.0),
        child: new Center(
          child: new Column(
            children: <Widget>[
              new Text('Value = ${_value}'),
              new IconButton(icon: new Icon(Icons.add), onPressed: _add),
              new IconButton(icon: new Icon(Icons.remove), onPressed: _subtract),
            ],
          ),
        ),
      ),
    );
  }
}