public boolean removeBookmark(long bookmarkId) {
   if (mDb == null) {
     open();
     if (mDb == null) {
       return false;
     }
   }
   clearBookmarkTags(bookmarkId);
   return mDb.delete(BookmarksTable.TABLE_NAME, BookmarksTable.ID + "=" + bookmarkId, null) == 1;
 }