def insertDomain(self, domain, indegree=0, outdegree=0):
		'''增加一个域名'''
		cur = self.conn.cursor()
		cur.execute("INSERT INTO Domains VALUES (NULL,?,?,?)", (domain, indegree, outdegree))
		# 写入到文件中
		self.conn.commit()
def remove_item(self, item):
    item_position = self._get_item_position(item)
    if item_position < len(self._items) - 1:
      next_item_position = item_position + 1
      self._items[next_item_position].item_widget.grab_focus()