我想让我的联系人和拨号器应用程序在flutter中成为默认设置

dependencies:
  contacts_service: ^0.6.2
  permission_handler: ^12.0.0
  url_launcher: ^6.0.0

import 'package:flutter/material.dart';
import 'package:contacts_service/contacts_service.dart';
import 'package:permission_handler/permission_handler.dart';
import 'package:url_launcher/url_launcher.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Contact Dialer',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  Iterable<Contact> _contacts;

  @override
  void initState() {
    super.initState();
    _getContacts();
  }

  Future<void> _getContacts() async {
    if (await Permission.contacts.request().isGranted) {
      var contacts = await ContactsService.getContacts();
      setState(() {
        _contacts = contacts;
      });
    }
  }

  void _launchDialer(String phoneNumber) async {
    var url = 'tel:$phoneNumber';
    if (await canLaunch(url)) {
      await launch(url);
    } else {
      throw 'Could not launch $url';
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Contact Dialer'),
      ),
      body: _contacts != null
          ? ListView.builder(
              itemCount: _contacts.length,
              itemBuilder: (context, index) {
                var contact = _contacts.elementAt(index);
                return ListTile(
                  title: Text(contact.displayName ?? ''),
                  subtitle: Text(contact.phones.isNotEmpty
                      ? contact.phones.first.value
                      : ''),
                  onTap: () {
                    _launchDialer(contact.phones.isNotEmpty
                        ? contact.phones.first.value
                        : '');
                  },
                );
              },
            )
          : Center(
              child: CircularProgressIndicator(),
            ),
    );
  }
}