// 在使用该函数之前最好先判断数据库中movieList这个表是否为空
 public List<UriInstance> queryFromUserID(int userID) {
   DatabaseHelper dbHelper = new DatabaseHelper(context, "CAMO_db1");
   SQLiteDatabase db = dbHelper.getWritableDatabase();
   Cursor cursor =
       db.query(
           "playList",
           new String[] {"userID", "uri", "classType", "name", "mediaType"},
           "userID=?",
           new String[] {Integer.toString(userID)},
           null,
           null,
           null);
   // UriInstance item = new UriInstance();
   String uri = null;
   String classType = null;
   String name = null;
   String mediaType = null;
   List<UriInstance> list = new ArrayList<UriInstance>();
   while (cursor.moveToNext()) {
     uri = cursor.getString(cursor.getColumnIndex("uri"));
     classType = cursor.getString(cursor.getColumnIndex("classType"));
     name = cursor.getString(cursor.getColumnIndex("name"));
     mediaType = cursor.getString(cursor.getColumnIndex("mediaType"));
     RdfFactory factory = RdfFactory.getInstance();
     UriInstance item = factory.createInstance(uri, mediaType, classType, name);
     list.add(item);
   }
   dbHelper.close();
   return list;
 }
 public static List<UriInstance> viewFavoredArtist(User user, UriInstance mediaInst) {
   List<UriInstance> artists = new ArrayList<UriInstance>();
   Object[] paramValues = {user.getId(), mediaInst.getUri()};
   String naiveAritsts =
       WebService.getInstance()
           .runFunction(ServerParam.INTERESET_GP_URL, "getFavoredArtist", paramValues);
   if (naiveAritsts.equals(ServerParam.NETWORK_ERROR1)) return artists;
   if (naiveAritsts.length() == 0) return artists;
   List<String> naiveAritstList = SetSerialization.deserialize2(naiveAritsts);
   for (String naiveArtist : naiveAritstList) {
     List<String> naiveTermList = SetSerialization.deserialize1(naiveArtist);
     if (naiveTermList.size() == 3) {
       UriInstance inst =
           RdfFactory.getInstance()
               .createInstance(
                   naiveTermList.get(0),
                   mediaInst.getMediaType(),
                   naiveTermList.get(2),
                   SetSerialization.instNameNomalize(naiveTermList.get(1)));
       artists.add(inst);
     }
   }
   return artists;
 }