textinput_testapp.py

from kivy.uix.floatlayout import FloatLayout
from kivy.app import runTouchApp
from kivy.lang import Builder
from kivy.clock import Clock
from kivy.logger import Logger
from time import time

class RootWidget(FloatLayout):
    scheduled_testing = False

    def __init__(self, **kwargs):
        super(RootWidget, self).__init__(**kwargs)

    def schedule_testing(self,):
        if not self.scheduled_testing:
            Clock.schedule_interval(self.do_test, 0)

    def do_test(self, *args):
        next_widget = None
        for i, x in enumerate(self.inp_widgets):
            if x.is_focusable:
                next_widget = i + 1
                if next_widget == 4:
                    next_widget = 0
                x.is_focusable = False
                self.inp_widgets[next_widget].is_focusable = True
                self.inp_widgets[next_widget].focus = True
                break
        print('NEW FOCUS', next_widget)

runTouchApp(Builder.load_string('''
<TestInput@TextInput>:
    size_hint: 0.5, 0.5
    # foreground_color:
    background_active: ''
    background_normal: ''
    background_disabled_normal: ''
    background_color: (0.5, 0.5, 0.5, 1) if not self.focus else (0.9, 0.9, 0.9, 1)
    multiline: False
    text: 'focus and focusable' if self.focus and self.is_focusable else 'focusable' if self.is_focusable else ''
    canvas.after:
        Color:
            rgba: (1, 0, 0, 1) if self.is_focusable else (1, 0, 0, 0)
        Rectangle:
            pos: self.pos
            size: int(self.width), int(self.height * 0.2)

RootWidget:
    inp_widgets: [inp1, inp2, inp3, inp4]
    Button:
        size_hint: 0.5, 0.1
        pos_hint: {'center_x': 0.5, 'center_y': 0.6}
        text: 'Do test'
        on_press: root.schedule_testing()

    GridLayout:
        cols: 2
        rows: 2
        size_hint: 0.7, 0.5
        pos_hint: {'center_x': 0.5, 'center_y': 0.3}
        TestInput:
            id: inp1
            focus: True
        TestInput:
            id: inp2
        TestInput:
            id: inp3
        TestInput:
            id: inp4
'''))