¿Cómo puedo configurar la posición (coordenadas X, Y) de un diseño de cuadrícula en Kivy?

Question

Me he dado cuenta de que cuando realiza botones usando el diseño de la cuadrícula en Kivy, se crean en (0,0) y se mueven sobre una cantidad de espacios dependiendo de la longitud y el ancho de los botones anteriores. Sin embargo, me gustaría tener una cuadrícula de 3x4 en el medio de la parte inferior de la pantalla.

Lo tengo hasta ahora:

import kivy
from kivy.uix.gridlayout import GridLayout
from kivy.app import App
from kivy.uix.button import Button

class CalcApp(App):
    def build(self):
        layout = GridLayout(cols=3, row_force_default=True, row_default_height=50)
        layout.add_widget(Button(text='1', size_hint_x=None, width=100))
        layout.add_widget(Button(text='2', size_hint_x=None, width=100))
        layout.add_widget(Button(text='3', size_hint_x=None, width=100))
        layout.add_widget(Button(text='4', size_hint_x=None, width=100))
        layout.add_widget(Button(text='5', size_hint_x=None, width=100))
        layout.add_widget(Button(text='2', size_hint_x=None, width=100))
        layout.add_widget(Button(text='6', size_hint_x=None, width=100))
        layout.add_widget(Button(text='7', size_hint_x=None, width=100))
        layout.add_widget(Button(text='8', size_hint_x=None, width=100))
        layout.add_widget(Button(text='9', size_hint_x=None, width=100))
        layout.add_widget(Button(text='0', size_hint_x=None, width=100))
        layout.add_widget(Button(text='Enter', size_hint_x=None, width=100))
        return layout

CalcApp().run()

Entonces, ¿cómo cambio la posición?

Answer 1

import kivy
from kivy.uix.gridlayout import GridLayout
from kivy.app import App
from kivy.uix.button import Button

class CalcApp(App):
    def build(self):
        layout = GridLayout(cols=3, row_force_default=True, row_default_height=50,
            pos_hint={'center_x':.5} , size_hint=(None, None))
            # ^ position grid in mid horizontally, ^ make grid use custom
            # size.
        # Bind the size of the gridlayout of to it's minimum_size(calculated
        # by children size)
        layout.bind(minimum_size = layout.setter('size'))
        # bind the top of the grid to it's height'
        layout.bind(height = layout.setter('top'))
        for x in (1, 2, 3, 4, 5, 2, 6, 7, 8, 9, 0):
            layout.add_widget(Button(text=str(x), size_hint_x=None, width=100))
        layout.add_widget(Button(text='Enter', size_hint_x=None, width=100))
        return layout

CalcApp().run()

El mismo código usando KV LANG ::

import kivy

from kivy.uix.gridlayout import GridLayout
from kivy.app import App
from kivy.lang import Builder

Builder.load_string('''
# a template Butt of type Button
[Butt@Button]
    # ctx.'attribute_name' is used to access the 
    # attributes defined in the instance of Butt.
    text: ctx.text
    # below vars are constant for every instance of Butt
    size_hint_x: None
    width: 100

<CalcApp>:
    cols: 3
    row_force_default: True
    row_default_height: 50
    pos_hint: {'center_x':.5}
    size_hint: (None, None)
    # size is updated whenever minimum_size is.
    size: self.minimum_size
    # top is updated whenever height is.
    top: self.height
    Butt:
        text: '1'
    Butt:
        text: '2'
    Butt:
        text: '3'
    Butt:
        text: '4'
    Butt:
        text: '5'
    Butt:
        text: '2'
    Butt:
        text: '6'
    Butt:
        text: '7'
    Butt:
        text: '8'
    Butt:
        text: '9'
    Butt:
        text: '0'
    Butt:
        text: 'Enter'
''')

class CalcApp(App, GridLayout):

    def build(self):
        return self

CalcApp().run()