main.dart

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: 'Flutter Demo',
      theme: ThemeData.dark(),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key}) : super(key: key);


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

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Demo"),
      ),
      body:  Container(
        child: Padding(
          padding: const EdgeInsets.all(20.0),
          child: CardWidget(),
        ),
      )
    );
  }
}

class CardWidget extends StatelessWidget {
  const CardWidget({
    Key key,
  }) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return DecoratedBox(
      decoration: BoxDecoration(borderRadius: BorderRadius.circular(10),color: Colors.grey[800]),
      child: Padding(
        padding: const EdgeInsets.all(10.0),
        child: Column(
          mainAxisSize: MainAxisSize.min,
          crossAxisAlignment: CrossAxisAlignment.stretch,
          children: <Widget>[
            Text("Lorem ipsum dolor sit amet", style: TextStyle(fontSize: 50),),
            Text("Lorem ipsum dolor sit amet", style: TextStyle(fontSize: 50),),
            Text("Lorem ipsum dolor sit amet", style: TextStyle(fontSize: 50),),
          ],
        ),
      ),
    );
  }
}