import 'package:flutter/material.dart';
import 'package:qr_flutter/qr_flutter.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: Scaffold(
        appBar: AppBar(),
        body: Row(
          children: <Widget>[
            Expanded(child: QrImage(
              data: 'datadatadatadatadatadatadatadatadata',
              padding: EdgeInsets.zero,
            )),
            Expanded(child: QrImage(
              data: 'datadatadatadatadatadatadatadatadata',
              padding: EdgeInsets.all(5),
            )),
            Expanded(child: QrImage(
              data: 'datadatadatadatadatadatadatadatadata',
              padding: EdgeInsets.all(10),
            )),
            Expanded(child: QrImage(
              data: 'datadatadatadatadatadatadatadatadata',
              padding: EdgeInsets.all(15),
            )),
          ],
        ),
      ),
    );
  }
}

Container(
  width: 80,
  child: QrImage(
    data: 'datadatadatadatadatadatadatadatadata',
    padding: EdgeInsets.zero,
  ),
),