《Beginning Android Games》付出基本框架的实现(4)

最后的部分是剩下的关于音乐实现的部分，与最先给出的抽象接口/类对应，于音乐有关的三个类分别对应Audio，Music，Sound的具体实现，Audio是两者的统一管理，程序通过Audio来取得Music或Sound，下面是3者的具体实现

public class AndroidAudio implements Audio {	AssetManager assets;	SoundPool soundPool;		public AndroidAudio(Activity activity){		activity.setVolumeControlStream(AudioManager.STREAM_MUSIC);		this.assets=activity.getAssets();		this.soundPool=new SoundPool(20,AudioManager.STREAM_MUSIC,0);	}		@Override	public Music newMusic(String filename) {		try {			AssetFileDescriptor assetDescriptor=assets.openFd(filename);			return new AndroidMusic(assetDescriptor);		} catch (IOException e) {			throw new RuntimeException("Couldn't load music '"+filename+"'");		}	}	@Override	public Sound newSound(String filename) {		try{			AssetFileDescriptor assetDescriptor=assets.openFd(filename);			int soundId=soundPool.load(assetDescriptor, 0);			return new AndroidSound(soundPool,soundId);		} catch (IOException e) {			throw new RuntimeException("Couldn't load sound '"+filename+"'");		}	}}

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public class AndroidSound implements Sound {	int soundId;	SoundPool soundPool;		public AndroidSound(SoundPool soundPool, int soundId){		this.soundId=soundId;		this.soundPool=soundPool;	}		@Override	public void dispose() {		soundPool.unload(soundId);	}	@Override	public void play(float volume) {		soundPool.play(soundId, volume, volume, 0, 0, 1);	}}

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public class AndroidMusic implements Music, OnCompletionListener {	MediaPlayer mediaPlayer;	boolean isPrepared =false;		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");		}	}		@Override	public void dispose() {		if(mediaPlayer.isPlaying()){			mediaPlayer.stop();		}		mediaPlayer.release();	}	@Override	public boolean isLooping() {		return mediaPlayer.isLooping();	}	@Override	public boolean isPlaying() {		return mediaPlayer.isPlaying();	}	@Override	public boolean isStopped() {		return !isPrepared;	}	@Override	public void pause() {	}	@Override	public void play() {		if(mediaPlayer.isPlaying()){			return;		}		try{			synchronized (this) {				if(!isPrepared){					mediaPlayer.prepare();				}				mediaPlayer.start();			}		} catch (IllegalStateException e){			e.printStackTrace();		} catch (IOException e){			e.printStackTrace();		}	}	@Override	public void setLooping(boolean looping) {		mediaPlayer.setLooping(looping);	}	@Override	public void setVolume(float volume) {		mediaPlayer.setVolume(volume, volume);	}	@Override	public void stop() {		mediaPlayer.stop();		synchronized (this) {			isPrepared=false;		}	}	@Override	public void onCompletion(MediaPlayer arg0) {		synchronized (this) {			isPrepared=false;		}	}}