main.dart

import 'package:flutter/material.dart';

void main() => runApp(new MyApp());
class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Flutter App',
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {

    return new MaterialApp(
      home: new Scaffold(
        appBar: new AppBar(title: const Text('Modal bottom sheet')),
        body: new Center(
          child: new RaisedButton(
            child: const Text('SHOW BOTTOM SHEET'),
            onPressed: () {
              showModalBottomSheet<void>(context: context, builder: (BuildContext context) {
                return new Container(
                  child: new Padding(
                    padding: const EdgeInsets.all(32.0),
                    child: new Text('This is the modal bottom sheet. Click anywhere to dismiss.',
                      textAlign: TextAlign.center,
                      style: new TextStyle(
                        color: Theme.of(context).accentColor,
                        fontSize: 24.0
                      )
                    )
                  )
                );
              });
            }
          )
        )
      )
    );
  }
}