ActionScript 3.0 Design Patterns

Example: Music Playlists | 221

The filename of the song clip is passed to the parameterized constructor and set to the

sNameproperty. Theplay( )method loads the songs from a subfolder calledmedia. The

event handler calledsongLoadedis registered to listen to theEvent.COMPLETEevent (line

25). When the song is loaded, thesongLoaded( )method pushes the song into the

aSongQueueplay queue (line 32). It then calls theplayIfIdle( )method that determines

if a song is playing and if not, gets the song fromaSongQueueusing the Shift function

(line 51), starts to play the song, and assigns it to thesoundChannelsound channel (line

56). TheaSongQueuearray functions as a song queue (first-in first-out). The event han-

dler calledplayDone is registered to listen to theEvent.SOUND_COMPLETE event (line 57).

When the sound stops playing, theEvent.SOUND_COMPLETE event will trigger the

playDone( ) method that calls theplayIfIdle( ) method again.

We can now create some playlists and listen to some music.

Building Composite Playlists

Let’s develop two playlists and embed them into a larger playlist. The following code

should be executed from the document class of a Flash document.

// create playlist

var drumlicks:Playlist = new Playlist("drum licks");

drumlicks.add(new Song("bongo.mp3"));

drumlicks.add(new Song("tabla.mp3"));

drumlicks.add(new Song("djembe.mp3"));

// create another playlist

var guitariffs:Playlist = new Playlist("guitar riffs");

guitariffs.add(new Song("acousticguitar.mp3"));

guitariffs.add(new Song("electricguitar.mp3"));

// create composite playlist

var eclectic:Playlist = new Playlist("eclectic");

eclectic.add(drumlicks);

eclectic.add(new Song("balladpiano.mp3"));

eclectic.add(guitariffs);

eclectic.play( );

The example application will first build the playlist named “drum licks.” It will then

build another playlist called “guitar riffs.” Finally, it will build and play a new

58 soundChannel.addEventListener

(Event.SOUND_COMPLETE, this.playDone);

59 }

60 }

61 }

62 }

63 }

Example 6-10. Song.as