利用Android怎么编写一个本地音乐播放器

public class PlayMusicService extends Service {

 //绑定服务 调用服务的方法。
 @Override
 public IBinder onBind(Intent intent) {
  return null;
 }

}

public class MainActivity extends Activity {
 private EditText et_path;

 private MediaPlayer mediaPlayer;

 private Button bt_play,bt_pause,bt_stop,bt_replay;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);
 et_path = (EditText) findViewById(R.id.et_path);
 bt_play = (Button) findViewById(R.id.bt_play);
 bt_pause = (Button) findViewById(R.id.bt_pause);
 bt_stop = (Button) findViewById(R.id.bt_stop);
 bt_replay = (Button) findViewById(R.id.bt_replay);
 }
 /**
 * 播放
 * @param view
 */
 public void play(View view) {
 String filepath = et_path.getText().toString().trim();
 File file = new File(filepath);
 if(file.exists()){
  try {
  mediaPlayer = new MediaPlayer();
  mediaPlayer.setDataSource(filepath);//设置播放的数据源。
  mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
  mediaPlayer.prepare();//准备开始播放 播放的逻辑是c代码在新的线程里面执行。
  mediaPlayer.start();
  bt_play.setEnabled(false);
  mediaPlayer.setOnCompletionListener(new OnCompletionListener() {
   @Override
   public void onCompletion(MediaPlayer mp) {
   bt_play.setEnabled(true);
   }
  });
  } catch (Exception e) {
  e.printStackTrace();
  Toast.makeText(this, "播放失败", 0).show();
  }
 }else{
  Toast.makeText(this, "文件不存在，请检查文件的路径", 0).show();
 }
 }
 /**
 * 暂停
 * @param view
 */
 public void pause(View view) {
 if("继续".equals(bt_pause.getText().toString())){
  mediaPlayer.start();
  bt_pause.setText("暂停");
  return;
 }
 if(mediaPlayer!=null&&mediaPlayer.isPlaying()){
  mediaPlayer.pause();
  bt_pause.setText("继续");
 }
 }
 /**
 * 停止
 * @param view
 */
 public void stop(View view) {
 if(mediaPlayer!=null&&mediaPlayer.isPlaying()){
  mediaPlayer.stop();
  mediaPlayer.release();
  mediaPlayer = null;
 }
 bt_pause.setText("暂停");
 bt_play.setEnabled(true);
 }
 /**
 * 重播
 * @param view
 */
 public void replay(View view) {
 if(mediaPlayer!=null&&mediaPlayer.isPlaying()){
  mediaPlayer.seekTo(0);
 }else{
  play(view);
 }
 bt_pause.setText("暂停");
 }

}