How to Add Audio File in Flutter Application?

dependencies:
     flutter:
       sdk: flutter
     audioplayers: ^6.4.0

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

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(debugShowCheckedModeBanner: false, home: audio());
  }
}

class audio extends StatefulWidget {
  @override
  _audioState createState() => _audioState();
}

class _audioState extends State<audio> {
  // Audio player for background music
  final AudioPlayer audioPlayer = AudioPlayer();

  // Play audio
  void _playAudio() {
    // Play background music
    audioPlayer.play(AssetSource("ringtone.mp3"));
  }

  // Stop audio
  void _stopAudio() {
    // Pause background music
    audioPlayer.pause();
  }

  @override
  void dispose() {
    // Dispose audio player
    audioPlayer.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        centerTitle: true,
        title: const Text(
          'Audio player Application',
          style: TextStyle(fontSize: 25),
        ),
        backgroundColor: Colors.green[700],
        foregroundColor: Colors.white,
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            ElevatedButton(
              onPressed: _playAudio,
              child: const Text(
                'Play',
                style: TextStyle(
                  fontSize: 16,
                  fontWeight: FontWeight.bold,
                  color: Colors.white,
                ),
                textAlign: TextAlign.center,
              ),
              style: ElevatedButton.styleFrom(
                backgroundColor: Colors.green[700],
                shape: RoundedRectangleBorder(
                  borderRadius: BorderRadius.circular(10),
                ),
                padding: EdgeInsets.all(8),
              ),
            ),
            SizedBox(height: 20),
            ElevatedButton(
              onPressed: _stopAudio,

              child: const Text(
                'Stop',
                style: TextStyle(
                  fontSize: 16,
                  fontWeight: FontWeight.bold,
                  color: Colors.white,
                ),
                textAlign: TextAlign.center,
              ),
              style: ElevatedButton.styleFrom(
                backgroundColor: Colors.green[700],
                shape: RoundedRectangleBorder(
                  borderRadius: BorderRadius.circular(10),
                ),
                padding: EdgeInsets.all(8),
              ),
            ),
          ],
        ),
      ),
    );
  }
}