Qpython Kivy TextInput focus is not working

Question

Focusing on the TextInput ends this simple Python script using Qpython on an Android phone

from kivy.lang import Builder
from kivy.base import runTouchApp
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.textinput  import TextInput
from kivy.uix.label        import Label

Builder.load_string("""
#:import kivy kivy
#:import sys sys

<Home>:
    orientation: "vertical"

    Label:
        text: "testing textinput problem"
    TextInput:
        text: "123"

    Label:
        text: "kivy version %s"  %   kivy.__version__ 

 """)

 class Home (BoxLayout):
    pass

 runTouchApp (Home() )  

There is no error message in the Runtime Log.

The error does not occur when the script is run on the PC.

The error occurs after Qpython switched to Kivy 1.8