Get Textfield Text Input Value On Button Onclick Using Flutter

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
        home: Scaffold(
          appBar: AppBar(
            backgroundColor: Color(0xFFFFC107),
            title: Text('Get Text Field Text Value'),
            centerTitle: true,
          ),
            body: GetTextFieldValue()
        )
    );
  }
}

class GetTextFieldValue extends StatefulWidget {
  _TextFieldValueState createState() => _TextFieldValueState();
}

class _TextFieldValueState extends State<GetTextFieldValue> {
  final textFieldValueHolder = TextEditingController();
  String result = '';
  getTextInputData(){
    setState(() {
      result = textFieldValueHolder.text;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              Container(
                  width: 280,
                  padding: EdgeInsets.all(10.0),
                  child: TextField(
                    controller: textFieldValueHolder,
                    autocorrect: true,
                    decoration: InputDecoration(hintText: 'Enter Some Text'),
                  )
              ),

              RaisedButton(
                onPressed: getTextInputData,
                color: Color(0xFFFFC107),
                textColor: Colors.white,
                padding: EdgeInsets.fromLTRB(10, 10, 10, 10),
                child: Text('Get Text Field Entered Data'),
              ),

              Padding(
                  padding: EdgeInsets.all(8.0),
                  child :
                  Text("Entered Text is = $result", style: TextStyle(fontSize: 20))
              )

            ],
          ),
        ));
  }
}