CountryCodePicker/example/lib/main.dart

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

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

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

class _MyAppState extends State<MyApp> {
  @override
  void initState() {
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
        home: new Scaffold(
            appBar: new AppBar(
              title: const Text('CountryPicker Example'),
            ),
            body: new Center(
              child: new CountryCodePicker(
                  onChanged: print,
                  // Initial selection and favorite can be one of code ('IT') OR dial_code('+39')
                  initialSelection: 'IT',
                  // showCountryOnly: true,
                  favorite: ['+39', 'FR']),
            )));
  }
}