Usig Kivy how can I generate scaled buttons in a scrollview

Question

I'm pretty new to kivy and I'm having some trouble with sizing and positioning the widgets, I'm trying to generate buttons that will be in a gridlayout inside a scrollview. When I press the button in the lower right corner I want to generate some buttons scaled to the width of that button.

But this is how the buttons turn out

class RootWidget(BoxLayout):
    pass

class CustomLayout(FloatLayout):

    def __init__(self, **kwargs):
        # make sure we aren't overriding any important functionality
        super(CustomLayout, self).__init__(**kwargs)

        with self.canvas.before:
            Color(0, 1, 0, 1)  # green; colors range from 0-1 instead of 0-255
            self.rect = Rectangle(size=self.size, pos=self.pos)

        self.bind(size=self._update_rect, pos=self._update_rect)

    def _update_rect(self, instance, value):
        self.rect.pos = instance.pos
        self.rect.size = instance.size

class MainApp(App):

    def build(self):
        root = RootWidget()
        c = CustomLayout()
        root.add_widget(c)

        def on_enter(self):
            func = Function()
            buttons = func.buttons()
            root.add_widget(buttons)

        get_buttons = Button(
            text='Get links',
            size_hint=(.5, .10),
            pos=(20, 20))
        root.add_widget(get_buttons)

        get_buttons.bind(on_press=on_enter)
        return root

class Function:
    def buttons(self):
        layout = GridLayout(cols=1, padding=1, spacing=10,
                size_hint=(None, None), width=20)

        layout.bind(minimum_height=layout.setter('height'))
        for buttn in range(20):
            btn = Button(text='test', size=(20, 50),
                         size_hint=(None, None))
            layout.add_widget(btn)
        # create a scroll view, with a size < size of the grid
        root = ScrollView(size_hint=(None, None), size=(20, 500),
                pos_hint={'center_x': .5, 'center_y': .5}, do_scroll_x=False)

        root.add_widget(layout)
    return root

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

Answer 1

I strongly recommend you using kv file to describe GUI, because it's much easier to read, and therefore maintain. Look at this example:

test.kv:

#:kivy 1.9.0
GridLayout:
    rows: 1

    LeftArea:
    RightArea:


<LeftArea@FloatLayout>:

    canvas:
        Color:
            rgb: 0, 1, 0
        Rectangle:
            size: self.size
            pos: self.pos


<RightArea@GridLayout>:
    cols: 1
    size_hint_x: 0.3
    spacing: '10dp'

    ScrollView:
        LinksGrid:
            id: links_grid

    GetLinksButton:
        links_grid: links_grid


<LinksGrid@GridLayout>:
    cols: 1
    spacing: '5dp'
    size_hint_y: None
    height: self.minimum_height


<GetLinksButton>:
    size_hint_y: 0.2
    text: 'get links'
    on_press: self.get_links()


<LinkButton>:
    size_hint_y: None
    height: '80dp'

main.py:

#!/usr/bin/env python
# -*- coding: utf-8 -*-
from kivy.app import App
from kivy.uix.button import Button


class GetLinksButton(Button):

    link_number = 1

    def get_links(self):
        for i in xrange(3):
            link_button = LinkButton(
                text='link number ' + str(self.link_number)
            )
            self.link_number += 1
            self.links_grid.add_widget(link_button)


class LinkButton(Button):
    pass


class Test(App):
    pass


Test().run()

Result: