how to show button in flutter

button.dart

import 'package:flutter/material.dart';

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

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        home: Scaffold(
            body: ListView(
      children: <Widget>[
        Container(
          margin: EdgeInsets.symmetric(horizontal: 100),
          child: new ConstrainedBox(
            constraints: const BoxConstraints(minWidth: double.infinity),
            child: new RaisedButton(
                color: Colors.blue,
                textColor: Colors.white,
                disabledColor: Colors.grey,
                disabledTextColor: Colors.black,
                splashColor: Colors.blueAccent,
                onPressed: () {},
                child: Text(
                  "Apply this buttom",
                  style: TextStyle(fontSize: 15),
                )
              ),
            ),
          )
        ],
      )
    ));
  }
}