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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 getMp3Infos() { Cursor cursor = getContentResolver().query( MediaStore.Audio.Media.EXTERNAL_CONTENT_URI, null, null, null, MediaStore.Audio.Media.DEFAULT_SORT_ORDER); List mp3Infos = new ArrayList(); 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 mp3Infos) { List mp3list = new ArrayList(); for (Iterator iterator = mp3Infos.iterator(); iterator.hasNext();) { Mp3Info mp3Info = (Mp3Info) iterator.next(); HashMap map = new HashMap(); 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。
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