@Override
 public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
   chatUserDB = ChatDao.getInstance(getContext());
   int upadte = chatUserDB.updateUserStatus(values, selection, selectionArgs);
   context.getContentResolver().notifyChange(USER_URI, null);
   return upadte;
 }
 @Override
 public int delete(Uri uri, String selection, String[] selectionArgs) {
   int result = matcher.match(uri);
   int count = 0;
   if (result == DELETE) {
     count = chatUserDB.deleteChatUser(selection, selectionArgs);
     context.getContentResolver().notifyChange(USER_URI, null);
   }
   return count;
 }
 @Override
 public boolean onCreate() {
   chatUserDB = ChatDao.getInstance(getContext());
   return true;
 }