获取外存卡上的音乐文件信息

android软件开发中，不可避免的需要涉及到音乐之类的开发知识。

在android系统中，我们不必自己开发程序去遍历外存卡的每一个文件夹或者逐个比较文件的后缀加到数组中慢慢弄。

android自己提供了一个类来帮助我们提取出内存卡中的音乐数据。如album,artist,id,the size of music 或者音乐文件的数量。

这个类便是ContentResolver.

使用这个类很简单，只是用context下的getContentResolver()方法，然后像操作数据库一样调用查询方法

query(Uri uri, String[] projection, String selection,String[] selectionArgs, String sortOrder)

获取到数据集cursor，有数据集就简单好办多了。

一个循环语句，加上判断，一个Stringbuffer类，足以把所有文件的信息调取出来。

StringBuffer sb = new StringBuffer();
for(cursor.moveToFirst();!cursor.isAfterLast();cursor.moveToNext())
{
id=cursor.getInt(cursor.getColumnIndexOrThrow(MediaStore.Audio.Media._ID));
title = cursor.getString(cursor.getColumnIndexOrThrow(MediaStore.Audio.Media.TITLE)); 
artist = cursor.getString(cursor.getColumnIndexOrThrow(MediaStore.Audio.Media.ARTIST));  
url = cursor.getString(cursor.getColumnIndexOrThrow(MediaStore.Audio.Media.DATA));  
duration = cursor.getInt(cursor.getColumnIndexOrThrow(MediaStore.Audio.Media.DURATION));
sb.append("id为"+number+"\n");
sb.append("title为"+title+"\n");
sb.append("artist为"+artist+"\n");
sb.append("url为"+url+"\n");
sb.append("duration为"+duration+"\n");
sb.append("\n");
number++;
}
text.setText(sb);
示例代码：
public class MainActivity extends Activity {
    TextView text;
    Cursor cursor;
    ContentResolver cp;
    int count=0;
    int id;
long size;
    String title,album,artist,url;
int duration;
int number=1;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
text=(TextView) findViewById(R.id.text);
cp=this.getContentResolver();
cursor=cp.query(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI, null, null,
null, MediaStore.Audio.Media.DEFAULT_SORT_ORDER);
count=cursor.getCount();
StringBuffer sb = new StringBuffer();
for(cursor.moveToFirst();!cursor.isAfterLast();cursor.moveToNext())
{
id=cursor.getInt(cursor.getColumnIndexOrThrow(MediaStore.Audio.Media._ID));
title = cursor.getString(cursor.getColumnIndexOrThrow(MediaStore.Audio.Media.TITLE)); 
artist = cursor.getString(cursor.getColumnIndexOrThrow(MediaStore.Audio.Media.ARTIST));  
url = cursor.getString(cursor.getColumnIndexOrThrow(MediaStore.Audio.Media.DATA));  
duration = cursor.getInt(cursor.getColumnIndexOrThrow(MediaStore.Audio.Media.DURATION));
sb.append("id为"+number+"\n");
sb.append("title为"+title+"\n");
sb.append("artist为"+artist+"\n");
sb.append("url为"+url+"\n");
sb.append("duration为"+duration+"\n");
sb.append("\n");
number++;
}
text.setText(sb);
}


@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}

}