InkWell is the material widget in flutter. It responds to the touch action as performed by the user. Inkwell will respond when the user clicks the button.

                      import 'package:flutter/material.dart';

void main() {
runApp(MyApp());
}

class MyApp extends StatelessWidget {
	
// This widget is the root of your application.
@override
Widget build(BuildContext context) {
	return MaterialApp(
	title: 'InkWell',
	theme: ThemeData(
		primarySwatch: Colors.blue,
	),
	home: MyHomePage(),
	debugShowCheckedModeBanner: false,
	);
}
}

class MyHomePage extends StatefulWidget {
@override
_MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {

String inkwell='';

@override
Widget build(BuildContext context) {
	return Scaffold(
	appBar: AppBar(
		title: Text('InkWell Widget'),
		backgroundColor: Colors.green,
		actions: <Widget>[
		Text(
			'GFG',
			textScaleFactor: 3,
		)
		],
	),
	backgroundColor: Colors.lightBlue[50],
	body: Center(
		child: Column(
		mainAxisAlignment: MainAxisAlignment.center,
		children: <Widget>[
			InkWell(
			onTap: () {
				setState(() {
				inkwell='Inkwell Tapped';
				});
			},
			onLongPress: () {
				setState(() {
				inkwell='InkWell Long Pressed';
				});
			},
			child: Container(
				color: Colors.green,
				width: 120,
				height: 70,
				child: Center(
					child: Text(
						'Inkwell',
						textScaleFactor: 2,
						style: TextStyle(fontWeight: FontWeight.bold),
					))),
			),

			Padding(
			padding: const EdgeInsets.all(8.0),
			child: Text(inkwell,textScaleFactor: 2,),
			)
		],
		),
	),
	);
}
}