How To Set Onclick Onpress Event On Raised Button Using Flutter

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  sampleFunction(){
    print('Function On Click Event Called.');
  }
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
        home: Scaffold(
          appBar: AppBar(
            backgroundColor: Color(0xFF4A148C),
            title: Text('Onclick Onpress Event'),
            centerTitle: true,
          ),
            body: Center(
                child: Column(
                  mainAxisAlignment: MainAxisAlignment.center,
                  children:[
                    RaisedButton(
                      child: Text(" Button With OnPress "),
                      onPressed: sampleFunction,
                      color: Color(0xFF4A148C),
                      textColor: Colors.white,
                      splashColor: Colors.grey,
                      padding: EdgeInsets.fromLTRB(10, 10, 10, 10),
                    )

                  ],
                )
            )
        )
    );
  }
}