textbox in kivy

def on_text(instance, value):
    print('The widget', instance, 'have:', value)

textinput = TextInput()
textinput.bind(text=on_text)

from kivy.base import runTouchApp
from kivy.lang import Builder

KV = ''' 
BoxLayout:
    CheckBox:
        id: cb
    TextInput:
        password: True
        multiline: cb.active
'''

runTouchApp(Builder.load_string(KV))