import 'package:flutter/material.dart';

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

class MyButton extends StatefulWidget
{
  @override
  MyButtonState createState() => new MyButtonState();
}

class MyButtonState extends State<MyButton>
{
  String flutterText = "";
  List<String> collection = ['Flutter', 'is', 'great'];
  int index = 0;

  void changeText()
  {
    setState
    (
      () 
      {
        flutterText = collection[index];
        index++;
        index = index % 3;
      }
    );
  }

  @override
  Widget build(BuildContext context)
  {
    return new Scaffold
    (
      appBar: new AppBar
      (
        title: new Text("Stateful Widget"),
        backgroundColor: Colors.orangeAccent,
      ),
      body: Center
      (
        child: new Column
        (
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>
          [
            new Text
            (
              flutterText,
              style: new TextStyle(fontSize: 40.0)
            ),
            new Padding
            (
              padding: new EdgeInsets.all(10.0)
            ),
            new RaisedButton
            (
              child: new Text
              (
                "Update",
                style: new TextStyle(color: Colors.white)
              ),
              color: Colors.blueAccent,
              onPressed: changeText,
            )
          ],
        )
      )
    );
  }
}