buttonfocus.kv

ButtonFocusRoot:

<ButtonFocusRoot>:
    ButtonFocusForm

<ButtonFocusForm>:
    orientation: "vertical"
    BoxLayout:
        height: "40dp"
        size_hint_y: None
        padding: [2, 2]
        spacing: 2

        TextInput:
            id: position_box
            size_hint_x: 25
            multiline: False
            input_filter: 'int'
            text: '<position>'
        Button:
            text: "Set Position"
            size_hint_x: 25
            on_press: root.set_position(position=position_box.text)

buttonfocus.kv (version 2)

ButtonFocusRoot:

<MyTextInput@TextInput>:

<ButtonFocusRoot>:
    ButtonFocusForm

<ButtonFocusForm>:
    orientation: "vertical"
    BoxLayout:
        height: "40dp"
        size_hint_y: None
        padding: [2, 2]
        spacing: 2

        MyTextInput:
            id: position_box
            size_hint_x: 25
            multiline: False
            input_filter: 'int'
            text: '<position>'
        Button:
            text: "Set Position"
            size_hint_x: 25
            on_press: root.set_position(position=position_box.text)

main.py

#!/usr/bin/env python
# -*- coding: UTF-8 -*-

import kivy
kivy.require('1.9.1')
from kivy.config import Config

# Adjust for RasPi touch screen size and no keyboard
Config.set('graphics', 'width', '800')
Config.set('graphics', 'height', '480')
# Config.set('kivy', 'keyboard_mode', 'systemanddock')

from kivy.app import App
from kivy.parser import parse_color as h2c
from kivy.uix.boxlayout import BoxLayout
from kivy.properties import NumericProperty
from kivy.logger import Logger
from kivy.clock import Clock, mainthread


class ButtonFocusForm(BoxLayout):

    def _refocus_position_box(self, arg1):
        self.ids['position_box'].text = '0'
        self.ids['position_box'].select_all()
        self.ids['position_box'].focus = True

    def set_position(self, position):
        if not position.isdigit():
            Logger.warning('ButtonFocusForm: set_position: Invalid position given!')
            # return
        else:
            Logger.info('ButtonFocusForm: set_position: You entered a number!')
        Clock.schedule_once(self._refocus_position_box, 0)


class ButtonFocusRoot(BoxLayout):
    # used for interacting with the system configuration
    use_kivy_settings = False  # disable the Kivy configuration settings panel
    position = NumericProperty()


class ButtonFocusApp(App):
    pass

if __name__ == '__main__':
    ButtonFocusApp().run()

main.py (version 2)

#!/usr/bin/env python
# -*- coding: UTF-8 -*-

import kivy
kivy.require('1.9.1')
from kivy.config import Config

# Adjust for RasPi touch screen size and no keyboard
Config.set('graphics', 'width', '800')
Config.set('graphics', 'height', '480')
# Config.set('kivy', 'keyboard_mode', 'systemanddock')

from kivy.app import App
from kivy.parser import parse_color as h2c
from kivy.uix.boxlayout import BoxLayout
from kivy.properties import NumericProperty
from kivy.logger import Logger
from kivy.clock import Clock, mainthread
from kivy.uix.textinput import TextInput


class MyTextInput(TextInput):

    def on_parent(self, widget, parent):
        self.focus = True


class ButtonFocusForm(BoxLayout):

    def _refocus_position_box(self, arg1):
        self.ids['position_box'].text = '0'
        self.ids['position_box'].select_all()
        self.ids['position_box'].focus = True

    def set_position(self, position):
        if not position.isdigit():
            Logger.warning('ButtonFocusForm: set_position: Invalid position given!')
            # return
        else:
            Logger.info('ButtonFocusForm: set_position: You entered a number!')
        Clock.schedule_once(self._refocus_position_box, 0)


class ButtonFocusRoot(BoxLayout):
    # used for interacting with the system configuration
    use_kivy_settings = False  # disable the Kivy configuration settings panel
    position = NumericProperty()


class ButtonFocusApp(App):
    pass

if __name__ == '__main__':
    ButtonFocusApp().run()