Xml music player

1

I am trying to create a simple music player with three songs, with a play button, a stop button, next and previous song buttons. It runs great, except for one flaw: If I click the play button while a sound is already playing, it will play anyway, and overlap on top of the first sound (very unpleasant). Here’s the code I am using:


var my_songs:XMLList;
var my_total:Number;

var my_sound:Sound;
var my_channel:SoundChannel;

var current_song:Number = 0;

var song_position:Number;
var isPlaying:Boolean = false;

var myXMLLoader:URLLoader = new URLLoader();
myXMLLoader.load(new URLRequest("playlist.xml"));
myXMLLoader.addEventListener(Event.COMPLETE, processXML);

function processXML(e:Event):void
{
	var myXML:XML = new XML(e.target.data);

	my_songs = myXML.SONG;
	my_total = my_songs.length();
	playSong(0);

	myXMLLoader.removeEventListener(Event.COMPLETE, processXML);
	myXMLLoader = null;
}

function playSong(mySong:Number):void
{
	var myTitle = my_songs[mySong]. @ TITLE;
	var myURL = my_songs[mySong]. @ URL;

	title_txt.text = myTitle;
	
	if (my_channel)
	{
		my_channel.stop();
		my_channel.removeEventListener(Event.SOUND_COMPLETE, onNext);
	}

	my_sound = new Sound();
	my_sound.load(new URLRequest(myURL));
	my_channel = my_sound.play();
	my_channel.addEventListener(Event.SOUND_COMPLETE, onNext);
}

next_btn.addEventListener(MouseEvent.CLICK, onNext);
function onNext(e:Event):void
{
	current_song++;
	if (current_song >= my_total)
	{
		current_song = 0;
	}
	playSong(current_song);
}

prev_btn.addEventListener(MouseEvent.CLICK, onPrev);
function onPrev(e:MouseEvent):void
{
	current_song--;
	if (current_song < 0)
	{
		current_song = my_total - 1;
	}
	playSong(current_song);
}

stop_btn.addEventListener(MouseEvent.CLICK, stopMusic);
 
function stopMusic(e:Event):void
{
    if(my_channel != null)
    {
        my_channel.stop();
        isPlaying = false;
    }
}
 
play_btn.addEventListener(MouseEvent.CLICK, playMusic);
 
function playMusic(e:Event):void
{
    if (!isPlaying)
    {
        my_channel = my_sound.play();
        isPlaying = true;
    }
}

How can I fix this? Thanks.