code: def _watchdog_queue(self):
          
          while not self.quit:
              k = self.queue.get()
              if k == self.keys['QUIT']:  # 退出
                  self.quit = True
                  self.switch_queue.put('main')
              elif k == self.keys['BYE']:
                  self.data.bye()
                  self.player.start_queue(self)
              elif k == self.keys['LOOP']:  # 单曲循环
                  self.set_loop()
              elif k == self.keys['RATE']:  # 加心/去心
                  self.set_rate()
              elif k == self.keys['OPENURL']:  # 打开当前歌曲豆瓣专辑
                  self.set_url()
              elif k == self.keys['HIGH']:  # 高品质音乐
                  self.set_high()
              elif k == self.keys['PAUSE']:  # 暂停
                  self.set_pause()
              elif k == self.keys['NEXT']:  # 下一首
                  self.player.next()
              elif k == '-' or k == '_':  # 减小音量
                  self.set_volume(-1)
              elif k == '+' or k == '=':  # 增大音量
                  self.set_volume(1)
              elif k == self.keys['MUTE']:  # 静音
                  self.set_mute()
              elif k in ['1', '2', '3', '4']:  # 主题选取
                  self.set_theme(k)
              elif k == self.keys['UP'] or k == 'B':  # 向下
                  self.up()
              elif k == self.keys['DOWN'] or k == 'A':  # 向上
                  self.down()
docs: 从queue里取出字符执行命令