How To Set Button Opacity Using Flutter Android App

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(
              centerTitle: true,
                backgroundColor: Colors.indigo[300],
                title: Text('Set Button Opacity')
            ),
            body: Center(
                child: Opacity(
                  opacity: 0.7,
                  child: RaisedButton(
                    onPressed: () {print('Button Clicked');},
                    child: Text(' Button With Opacity '),
                    color: Colors.indigo[300],
                    textColor: Colors.white,
                    padding: EdgeInsets.fromLTRB(10, 10, 10, 10),
                  ),
                )
            )
        )
    );
  }
}