안녕하세요 안드로이드스튜디오로 프로그램짜는데 좀도와주세요 음악파일추가

Question

package com.android.ch12_service;

      import android.app.Service;
      import android.content.Intent;
      import android.media.MediaPlayer;
      import android.os.IBinder;
      import android.util.Log;
      import android.widget.Toast;

public class MusicService extends Service {
      private static final String TAG = "MusicService";
      MediaPlayer player;

      @Override
      public IBinder onBind(Intent intent) {
         return null;
      }

      @Override
      public void onCreate() {
         Log.d(TAG, "onCreate()");

         player = MediaPlayer.create(this, R.raw.old_pop);
         player = MediaPlayer.create(this, R.raw.old_pop2);
         player = MediaPlayer.create(this, R.raw.old_pop3);
         player.setLooping(false); // Set looping
      }

버튼1,2,3에 올드팝1,2,3이 나오게끔 어떻게만드나요