kivy.py

<MyScreenManager>:
    orientation: 'vertical'
    canvas.before:
        Color:
            rgba: 1,1,1,1
        Rectangle:
            pos: self.pos
            size: self.size
    MainMenuScreen:
    FilmMenuScreen:
    FilmDescriptionScreen:
    MapScreen:


<MainMenuScreen>:
    name: 'MainMenuScreen'
    BoxLayout:
        orientation: 'vertical'
        Label:
            size_hint_y: None
            height: root.height / 7
            text: 'Main Menu'
            font_size: self.height / 2
            color: [0.5, 0.3, 0.81, 0.9]            
        GridLayout:
            cols: 2
            rows: 2
            Button:
                #text: 'Films'
                background_normal: 'pictures/film1.jpg'
                background_down: 'pictures/film1.jpg'
                border: 30, 30, 30, 30
                font_size: self.height / 3
                on_release: app.root.current = 'FilmMenuScreen'
            Button:
                text: 'Credits'
                font_size: self.height / 3
            Button:
                text: 'Map'
                font_size: self.height / 3
                on_release: app.root.current = 'MapScreen'
            Button:
                text: 'Settings'
                font_size: self.height / 3

<FilmMenuScreen>
    name: 'FilmMenuScreen'
    ScrollView:
        size_hint_y: None
        height: root.height
        GridLayout:
            id: film_box
            cols:1
            size_hint_y: None
            height: self.minimum_height
            Label:
                size_hint_y: None
                height: root.height / 7            
                text: 'Film menu'
                font_size: self.height / 2
                color: [0.5, 0.3, 0.81, 0.9]# [0,0,1,1]
    BoxLayout:
        Button:
            size_hint_y: None
            height: root.height / 7
            text: 'Go back'
            font_size: self.height / 2
            on_release: app.root.current = 'MainMenuScreen'

<MapScreen>
    name: 'MapScreen'
    GridLayout:
        cols: 1
        rows: 2
        Image:
            source: 'pictures/map.png'
            allow_strech: True
            keep_ratio: False
        Button:
            size_hint_y: None
            height: root.height / 7
            text: 'Go back'
            font_size: self.height / 2
            on_release: app.root.current = 'MainMenuScreen'

<FilmDescriptionScreen>:
    name: 'FilmDescriptionScreen'
    

python.py

#!/usr/bin/env python

from kivy.app import App

from kivy.uix.button        import Button
from kivy.uix.textinput     import TextInput
from kivy.uix.boxlayout     import BoxLayout
from kivy.uix.label         import Label
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.uix.scrollview    import ScrollView
from kivy.clock             import Clock

from functools import partial
import json


class FFDMApp(App):

    def build(self):
        sm = MyScreenManager()
        return sm

class MyScreenManager(ScreenManager):
    pass

class MainMenuScreen(Screen):
    pass

class FilmMenuScreen(Screen):

    def __init__(self, **kvargs):
        super(FilmMenuScreen, self).__init__(**kvargs)
        Clock.schedule_once(self.add_films, 0.1)

    def add_films(self, *args):

        with open('films.json', 'r') as f:
            films_database = json.load(f)

        for film in films_database:
            button = Button(text        = film,
                            size_hint_y = None)
            button.font_size = button.height / 2
            button.bind(on_press = partial(self.show_description_screen, 25))
            self.ids.film_box.add_widget(button)

    def show_description_screen(self, *args):
        self.manager.current = 'FilmDescriptionScreen'
        

class FilmDescriptionScreen(Screen):
    pass

class MapScreen(Screen):
    pass

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