This is a simple code snippet to use to explain how you can change text status as soon as a button is pressed in Flutter SDK and Dart. You can refer https://slcoderlk.blogspot.com/2018/03/how-to-change-text-status-as-soon-as.html to see whats happening in this code.

change_text.dart

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Converter App',
      theme: new ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: new Scaffold(
        appBar: new AppBar(
          title: new Text('Converter App'),
        ),
        body: new Center(
          child: new Converter(),
        ),
      )
    );
  }

}

class Converter extends StatefulWidget {
  @override
  _ConverterWidget createState() => new _ConverterWidget();
}

class _ConverterWidget extends State<Converter> {
  String value = "click Me";
  @override
  Widget build(BuildContext context) {
    return new Column(
      children: <Widget>[
        new Text(value),
        new RaisedButton(
          child: new Text('Click me'),
          onPressed: () {
            setState(() {
              value += ' Me';
            });
          },
        ),
      ],
    );
  }
}