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。