详解Android应用开发--MP3音乐播放器代码实现（一）

需求1：将内存卡中的MP3音乐读取出来并显示到列表当中

1.从数据库中查询所有音乐数据，保存到List集合当中，List当中存放的是Mp3Info对象

2.迭代List集合，把每一个Mp3Info对象的所有属性，保存到Map对象当中

3.定义一个List集合，把Map对象添加到List集合当中

4.通过定义一个SimpleAdpter,调用setAdpter方法，将数据显示到列表当中

/**
* 用于从数据库中查询歌曲的信息，保存在List当中
*
* @return
*/
public List<Mp3Info> getMp3Infos() {
  Cursor cursor = getContentResolver().query(
    MediaStore.Audio.Media.EXTERNAL_CONTENT_URI, null, null, null,
    MediaStore.Audio.Media.DEFAULT_SORT_ORDER);
  List<Mp3Info> mp3Infos = new ArrayList<Mp3Info>();
  for (int i = 0; i < cursor.getCount(); i++) {
    Mp3Info mp3Info = new Mp3Info();
    cursor.moveToNext();
    long id = cursor.getLong(cursor
      .getColumnIndex(MediaStore.Audio.Media._ID));  //音乐id
    String title = cursor.getString((cursor
      .getColumnIndex(MediaStore.Audio.Media.TITLE)));//音乐标题
    String artist = cursor.getString(cursor
      .getColumnIndex(MediaStore.Audio.Media.ARTIST));//艺术家
    long duration = cursor.getLong(cursor
      .getColumnIndex(MediaStore.Audio.Media.DURATION));//时长
    long size = cursor.getLong(cursor
      .getColumnIndex(MediaStore.Audio.Media.SIZE)); //文件大小
    String url = cursor.getString(cursor
      .getColumnIndex(MediaStore.Audio.Media.DATA));       //文件路径
  int isMusic = cursor.getInt(cursor
    .getColumnIndex(MediaStore.Audio.Media.IS_MUSIC));//是否为音乐
  if (isMusic != 0) {   //只把音乐添加到集合当中
    mp3Info.setId(id);
    mp3Info.setTitle(title);
    mp3Info.setArtist(artist);
    mp3Info.setDuration(duration);
    mp3Info.setSize(size);
    mp3Info.setUrl(url);
    mp3Infos.add(mp3Info);
    }
  }
return mp3Infos;
}

/**
   * 填充列表
   * @param mp3Infos
   */
  public void setListAdpter(List<Mp3Info> mp3Infos) {
    List<HashMap<String, String>> mp3list = new ArrayList<HashMap<String, String>>();
    for (Iterator iterator = mp3Infos.iterator(); iterator.hasNext();) {
      Mp3Info mp3Info = (Mp3Info) iterator.next();
      HashMap<String, String> map = new HashMap<String, String>();
      map.put("title", mp3Info.getTitle());
      map.put("Artist", mp3Info.getArtist());
      map.put("duration", String.valueOf(mp3Info.getDuration()));
      map.put("size", String.valueOf(mp3Info.getSize()));
      map.put("url", mp3Info.getUrl());
      mp3list.add(map);
    }
    mAdapter = new SimpleAdapter(this, mp3list,
        R.layout.music_list_item_layout, new String[] { "title", "Artist", "duration" },
        new int[] { R.id.music_title, R.id.music_Artist, R.id.music_duration });
    mMusiclist.setAdapter(mAdapter);
  }

实现效果如图：

需求2：点击列表的每一项，启动一个服务来播放音乐

1.   注册条目点击监听器OnItemClickListener

2.   定义一个实现OnItemClickListener接口的内部类

3.   定义一个继承Service的服务类PlayerServie

1.   注册条目点击监听器OnItemClickListener

mMusiclist = (ListView) findViewById(R.id.music_list);
    mMusiclist.setOnItemClickListener(new MusicListItemClickListener());
    mp3Infos = getMp3Infos();
    setListAdpter(getMp3Infos());

2.   定义一个实现OnItemClickListener接口的内部类

private class MusicListItemClickListener implements OnItemClickListener {
  @Override
  public void onItemClick(AdapterView<?> parent, View view, int position,
      long id) {
    if(mp3Infos != null) {
      Mp3Info mp3Info = mp3Infos.get(position);
      Log.d("mp3Info-->", mp3Info.toString());
      Intent intent = new Intent();
      intent.putExtra("url", mp3Info.getUrl());
      intent.putExtra("MSG", AppConstant.PlayerMsg.PLAY_MSG);
      intent.setClass(MainActivity.this, PlayerService.class);
      startService(intent);    //启动服务
    }
  }
}

3.   定义一个继承Service的服务类PlayerServie（未完善的Service类）

package com.wwj.sb.service; 

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

import com.wwj.sb.domain.AppConstant; 

@SuppressLint("NewApi")
public class PlayerService extends Service {
  private MediaPlayer mediaPlayer = new MediaPlayer();    //媒体播放器对象
  private String path;            //音乐文件路径
  private boolean isPause;          //暂停状态 

  @Override
  public IBinder onBind(Intent arg0) {
    return null;
  } 

  @Override
  public int onStartCommand(Intent intent, int flags, int startId) {
    if(mediaPlayer.isPlaying()) {
      stop();
    }
    path = intent.getStringExtra("url");
    int msg = intent.getIntExtra("MSG", 0);
    if(msg == AppConstant.PlayerMsg.PLAY_MSG) {
      play(0);
    } else if(msg == AppConstant.PlayerMsg.PAUSE_MSG) {
      pause();
    } else if(msg == AppConstant.PlayerMsg.STOP_MSG) {
      stop();
    }
    return super.onStartCommand(intent, flags, startId);
  } 

  /**
   * 播放音乐
   * @param position
   */
  private void play(int position) {
    try {
      mediaPlayer.reset();//把各项参数恢复到初始状态
      mediaPlayer.setDataSource(path);
      mediaPlayer.prepare(); //进行缓冲
      mediaPlayer.setOnPreparedListener(new PreparedListener(position));//注册一个监听器
    }
    catch (Exception e) {
      e.printStackTrace();
    }
  } 

  /**
   * 暂停音乐
   */
  private void pause() {
    if (mediaPlayer != null && mediaPlayer.isPlaying()) {
      mediaPlayer.pause();
      isPause = true;
    }
  } 

  /**
   * 停止音乐
   */
  private void stop(){
    if(mediaPlayer != null) {
      mediaPlayer.stop();
      try {
        mediaPlayer.prepare(); // 在调用stop后如果需要再次通过start进行播放,需要之前调用prepare函数
      } catch (Exception e) {
        e.printStackTrace();
      }
    }
  } 

  @Override
  public void onDestroy() {
    if(mediaPlayer != null){
      mediaPlayer.stop();
      mediaPlayer.release();
    }
  }
  /**
   *
   * 实现一个OnPrepareLister接口,当音乐准备好的时候开始播放
   *
   */
  private final class PreparedListener implements OnPreparedListener {
    private int positon; 

    public PreparedListener(int positon) {
      this.positon = positon;
    } 

    @Override
    public void onPrepared(MediaPlayer mp) {
      mediaPlayer.start();  //开始播放
      if(positon > 0) {  //如果音乐不是从头播放
        mediaPlayer.seekTo(positon);
      }
    }
  } 

}

以上代码实现了两个需求，显示音乐列表和实现列表点击事件启动Servic。下次会实现控制音乐播放的需求。希望对大家的学习有所帮助，也希望大家多多支持我们。