利用Android怎么編寫一個本地音樂播放器

public class PlayMusicService extends Service {

 //綁定服務 調用服務的方法。
 @Override
 public IBinder onBind(Intent intent) {
  return null;
 }

}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:tools="http://schemas.android.com/tools"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:orientation="vertical"
 tools:context=".MainActivity" >

 <EditText
  android:id="@+id/et_path"
  android:layout_width="fill_parent"
  android:layout_height="wrap_content"
  android:hint="請輸入要播放文件的路徑" />

 <LinearLayout
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:orientation="horizontal" >

  <Button
   android:id="@+id/bt_play"
   android:onClick="play"
   android:layout_width="0dip"
   android:layout_height="wrap_content"
   android:layout_weight="1"
   android:text="播放" />
  <Button
    android:id="@+id/bt_pause"
   android:onClick="pause"
   android:layout_width="0dip"
   android:layout_height="wrap_content"
   android:layout_weight="1"
   android:text="暫停" />
  <Button
    android:id="@+id/bt_stop"
   android:onClick="stop"
   android:layout_width="0dip"
   android:layout_height="wrap_content"
   android:layout_weight="1"
   android:text="停止" />
  <Button
    android:id="@+id/bt_replay"
   android:onClick="replay"
   android:layout_width="0dip"
   android:layout_height="wrap_content"
   android:layout_weight="1"
   android:text="重播" />
 </LinearLayout>

</LinearLayout>

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);//設置播放的數據源。
  mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
  mediaPlayer.prepare();//準備開始播放 播放的邏輯是c代碼在新的線程里面執行。
  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, "播放失敗", 0).show();
  }
 }else{
  Toast.makeText(this, "文件不存在，請檢查文件的路徑", 0).show();
 }
 }
 /**
 * 暫停
 * @param view
 */
 public void pause(View view) {
 if("繼續".equals(bt_pause.getText().toString())){
  mediaPlayer.start();
  bt_pause.setText("暫停");
  return;
 }
 if(mediaPlayer!=null&&mediaPlayer.isPlaying()){
  mediaPlayer.pause();
  bt_pause.setText("繼續");
 }
 }
 /**
 * 停止
 * @param view
 */
 public void stop(View view) {
 if(mediaPlayer!=null&&mediaPlayer.isPlaying()){
  mediaPlayer.stop();
  mediaPlayer.release();
  mediaPlayer = null;
 }
 bt_pause.setText("暫停");
 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("暫停");
 }

}