how to change the ui on urwid

Question

I am creating a small urwid app for my use, the structure is a Filler which has a Pile composed of several Text filed, followed by a Divider, an Edit, another Divier and finally a Text:

Text1
Text2
Text3
Divide
>> Edit
Divide
Textout

Now, I want to replace Text1 .. Text3 with other Text field, the exact number of those varies. I figure I should redraw the entire UI, but I got no response on draw_screen()

My class:

class main_ui(urwid.Filler):
  def __init__(self):
      self.body = welcom()
      self.options = self.body.options
      self.replay = self.body.replay
      self.ask = self.body.ask
      super(main_ui,self).__init__(self.body.pile,valign='top')
  def paint(self):
      super(main_ii,self).__init__(urwid.pile[urwid.Text('test')])

The welcom() function generates the above fields, and options is dict that holds information I need

I run the loop like this

def refresh(_loop,_data):
    m.new_point()
    _loop.draw_screen()
    _loop.set_alarm_in(2,refresh)


m = main_ui()
loop = urwid.MainLoop(m)
loop.set_alarm_in(2,refresh)
loop.run()

How can I update my ui?