1、增加一个类，这个类是继承Service的，如下。
package com.example.android.snake;

import android.app.Service;
import android.content.Intent;
import android.media.MediaPlayer;
import android.os.IBinder;

public class MusicServer extends Service {

private MediaPlayer mediaPlayer;

@Override
public IBinder onBind(Intent intent) {
// TODO Auto-generated method stub
return null;
}

@Override
public void onStart(Intent intent,int startId){
super.onStart(intent, startId);

if(mediaPlayer==null){

// R.raw.mmp是资源文件，MP3格式的
mediaPlayer = MediaPlayer.create(this, R.raw.mmp);
mediaPlayer.setLooping(true);
mediaPlayer.start();

}
}

@Override
public void onDestroy() {
// TODO Auto-generated method stub
super.onDestroy();
mediaPlayer.stop();
}
}

2、在AndroidManifest.xml中添加如下代码。

3、在Snake.java加入以下代码（红色为新加的)

package com.example.android.snake;

import android.app.Activity;
import android.os.Bundle;
import android.view.Window;
import android.widget.TextView;
import android.content.Intent;

public class Snake extends Activity {

private SnakeView mSnakeView;
private Intent intent = new Intent("com.angel.Android.MUSIC");

private static String ICICLE_KEY = "snake-view";

/**
* Called when Activity is first created. Turns off the title bar, sets up
* the content views, and fires up the SnakeView.
*
*/
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);

setContentView(R.layout.snake_layout);

//start background music
startService(intent);

mSnakeView = (SnakeView) findViewById(R.id.snake);
mSnakeView.setTextView((TextView) findViewById(R.id.text));

if (savedInstanceState == null) {
// We were just launched -- set up a new game
mSnakeView.setMode(SnakeView.READY);
} else {
// We are being restored
Bundle map = savedInstanceState.getBundle(ICICLE_KEY);
if (map != null) {
mSnakeView.restoreState(map);
} else {
mSnakeView.setMode(SnakeView.PAUSE);
}
}
}

@Override
protected void onPause() {
super.onPause();
// Pause the game along with the activity
mSnakeView.setMode(SnakeView.PAUSE);

stopService(intent);
}

@Override
public void onSaveInstanceState(Bundle outState) {
//Store the game state
outState.putBundle(ICICLE_KEY, mSnakeView.saveState());
}

}

这样运行游戏时候就能听到背景音乐了