An Android Game Development Framework - Beginning Android Games - page 195

Listing 5-4. AndroidMusic.java; Implementing the Music Interface
package com.badlogic.androidgames.framework.impl;
import java.io.IOException;
import android.content.res.AssetFileDescriptor;
import android.media.MediaPlayer;
import android.media.MediaPlayer.OnCompletionListener;
import com.badlogic.androidgames.framework.Music;
public class AndroidMusic implements Music, OnCompletionListener {
MediaPlayer mediaPlayer;
boolean isPrepared= false ;
The AndroidMusic class stores a MediaPlayer instance along with a Boolean called isPrepared .
Remember, we can only call MediaPlayer.start() / stop() / pause() when the MediaPlayer is
prepared. This member helps us keep track of the MediaPlayer 's state.
The AndroidMusic class implements the Music interface as well as the OnCompletionListener
interface. In Chapter 4, we briefly defined this interface as a means of informing ourselves about
when a MediaPlayer has stopped playing back a music file. If this happens, the MediaPlayer
needs to be prepared again before we can invoke any of the other methods. The method
OnCompletionListener.onCompletion() might be called in a separate thread, and since we set
the isPrepared member in this method, we have to make sure that it is safe from concurrent
modifications.
public AndroidMusic(AssetFileDescriptor assetDescriptor) {
mediaPlayer= new MediaPlayer();
try {
mediaPlayer.setDataSource(assetDescriptor.getFileDescriptor(),
assetDescriptor.getStartOffset(),
assetDescriptor.getLength());
mediaPlayer.prepare();
isPrepared= true ;
mediaPlayer.setOnCompletionListener( this );
} catch (Exception e) {
throw new RuntimeException("Couldn't load music");
}
}
In the constructor, we create and prepare the MediaPlayer from the AssetFileDescriptor that is
passed in, and we set the isPrepared flag, as well as register the AndroidMusic instance as an
OnCompletionListener with the MediaPlayer . If anything goes wrong, we throw an unchecked
RuntimeException once again.
public void dispose() {
if (mediaPlayer.isPlaying())
mediaPlayer.stop();
mediaPlayer.release();
}