main2.dart

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


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

class MeineApp extends StatefulWidget {
  @override
  _MeineAppState createState() => _MeineAppState();
}

class _MeineAppState extends State<MeineApp> {
  double aA=0;
  double bB=0;
  dynamic mneueBox=boxDeco(0.0, 0.0);
  void neueBox(){
    setState(() {
     aA=aA + 1.0;
     bB=bB + 1.0;
     mneueBox=boxDeco(aA, bB); 
    });
  }
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: "StateDemo",
      home: new Scaffold(
        body: new Row(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
           new Center(
             child: new Container(
               width: 50.0,
               height: 50.0,
               child: Center(child: new Text("Hallo"),),
               decoration: mneueBox,
             ),
           ),
           new IconButton(
             color: Colors.deepOrange,
             icon:Icon(Icons.star) ,
             onPressed:neueBox,
           )
          ],
        ),
      ),
      
    );
  }
}