CPF Gen Flutter

import 'package:flutter/material.dart';
import 'dart:math' show Random;

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

class CPFGen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        appBar: AppBar(
          title: Text(
            'Gerador de CPF',
          ),
        ),
        body: GeneratorScreen(),
      ),
    );
  }
}

class GeneratorScreen extends StatelessWidget {
  final TextEditingController _textEditingController = TextEditingController();
  @override
  Widget build(BuildContext context) {
    return Center(
      child: IntrinsicWidth(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          crossAxisAlignment: CrossAxisAlignment.stretch,
          children: <Widget>[
            TextField(
              enableInteractiveSelection: true,
              textAlign: TextAlign.center,
              showCursor: false,
              maxLines: 1,
              controller: _textEditingController,
              cursorColor: Theme.of(context).primaryColor,
              style: Theme.of(context).textTheme.subtitle1,
              decoration: InputDecoration(
                contentPadding: EdgeInsets.symmetric(horizontal: 10),
                filled: false,
                hintMaxLines: 1,
                hintText: 'Quantos CPFs?',
                hintStyle: Theme.of(context).textTheme.subtitle1,
                border: OutlineInputBorder(
                  borderRadius: BorderRadius.all(Radius.circular(5.0)),
                ),
              ),
              onChanged: (input) {
                print(_textEditingController.text);
              },
            ),
            RaisedButton(
              child: Text(
                'Gerar',
                style: TextStyle(fontSize: 14),
              ),
              onPressed: () {
                GeneratorAlgorithm generator = GeneratorAlgorithm();

                List<String> cpfs = List<String>.generate(
                    int.parse(_textEditingController.text), (_) {
                  return generator.generateCPF();
                });
                _textEditingController.clear();
                Navigator.push(
                  context,
                  MaterialPageRoute(
                    builder: (context) {
                      return Scaffold(
                        appBar: AppBar(title: Text('Resultados')),
                        body: ListView.builder(
                          itemCount: cpfs.length,
                          itemBuilder: (context, index) {
                            return ListTile(title: Text(cpfs[index]));
                          },
                        ),
                      );
                    },
                  ),
                );
              },
            ),
          ],
        ),
      ),
    );
  }
}

class GeneratorAlgorithm {
  String generateCPF() {
    final Random random = Random();
    List<int> buildCPF =
        List<int>.generate(9, (_) => random.nextInt(9), growable: true);

    for (int i = 0; i < 2; i++) {
      buildCPF.add(digit(buildCPF));
    }

    return buildString(buildCPF);
  }

  int digit(List<int> buildCPF) {
    int sum = 0;
    int index = buildCPF.length + 1;

    for (int i in buildCPF) {
      sum += i * index;
      index -= 1;
    }

    return verifySum(sum);
  }

  int verifySum(int sum) {
    return ((sum % 11) < 2) ? 0 : 11 - (sum % 11);
  }

  String buildString(List<int> buildCPF) {
    List<String> getNumbers = [];
    String formattedCPF = "";

    for (int i in buildCPF) {
      getNumbers.add(i.toString());
    }

    getNumbers.insert(3, ".");
    getNumbers.insert(7, ".");
    getNumbers.insert(11, "-");

    for (String i in getNumbers) {
      formattedCPF += i;
    }

    return formattedCPF;
  }
}