Kivy can't change image position with click

Question

I have a big problem about my code. I want to change screen background image's x position when I click button. Actually I think I am changing position correctly. Because im checking image's current position with other button. But there is a nothing on screen. Image is not moving anywhere. What is my fault or shouldn't I use widget to show image on screen ? Is there any way to do this little game.

My .py file:

from kivy.app import App
from kivy.uix.screenmanager import ScreenManager, Screen, NoTransition , FadeTransition
from kivy.properties import ObjectProperty, NumericProperty
from kivy.lang import Builder
from kivy.uix.gridlayout import GridLayout
from kivy.uix.layout import Layout
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.button import Button
from kivy.uix.label import Label
from kivy.uix.image import Image
from kivy.core.window import Window

Builder.load_file('jumpergame.kv')



class MainMenu(Screen):
    pass

class Dark(Screen):
    pass


class SettingsMenu(Screen):
    pass

class Game(Screen):

    first_image_py = ObjectProperty(None)

    def test(self):
        print(self.first_image_py.pos)

    def swipe(self):
        print(self.first_image_py.pos[0])
        self.first_image_py.pos[0] -= 100
        print(self.first_image_py.pos[0])


    def show_bg_first_pos(self):
        print('*******************')
        print('First Background [X] Position ==>',self.first_image_py.pos[0])
        print('First Background [Y] Position ==>',self.first_image_py.pos[1])
        return self.bg_first_pos_x,self.bg_first_pos_y

    def show_screen_size(self):
        print('*******************')
        print('Screen [X] Size ==>',self.width)
        print('Screen [Y] Size ==>',self.height)


    def show_bg_second_pos(self):
        print('*******************')


sm = ScreenManager()
sm.add_widget(MainMenu(name='mainmenu'))
sm.add_widget(SettingsMenu(name='settings'))
sm.add_widget(Game(name='game'))
sm.add_widget(Dark(name='dark'))

class JumperGame(App):
    def build(self):
        return sm

if __name__ == "__main__":
    JumperGame().run()

My .kv file :

<MainMenu>:

    BoxLayout:
        orientation : 'vertical'

        Label:
            text: 'JumperGame v1.00 \n          by 320V'
        Button:
            text: 'Start'
            on_press: root.manager.current = 'game'
        Button:
            text: 'Settings'
            on_press: root.manager.current = 'settings'

<SettingsMenu>:
    Button:
        text: 'BACK to MENU'
        on_press: root.manager.current = 'mainmenu'

<Game>:
    first_image_py : first_image_kv

    Widget:
        id: first_image_kv
        pos: 0,0

        canvas.before:
            Color:
                rgb: (1,1,1)
            Rectangle:

                source: 'bg.png'
                size: self.width  , self.height



    AnchorLayout:
        anchor_x : 'right'
        anchor_y : 'top'

        Button:
            text: 'Check image 1 pos'
            size_hint: .25,.1
            on_press: root.show_bg_first_pos()

    AnchorLayout:
        anchor_x : 'left'
        anchor_y : 'top'

        Button:
            text: 'Check Image 2 Pos'
            size_hint:.25,.1
            on_press: root.show_bg_second_pos()


    AnchorLayout:
        anchor_x : 'center'
        anchor_y : 'bottom'

        Button:
            text: 'Check Window Size'
            size_hint: .25 , .1
            on_press: root.show_screen_size()

    FloatLayout:
        canvas:
            Color:
                rgb: (1,1,1)
            Rectangle:
                id: bg_Image_Second
                source: 'bg.png'
                size: self.width  , self.height
                pos: root.width,root.height
        Button:
            text: 'Swipe Images'
            size_hint: .1,.1
            on_press: root.swipe()

        Button:
            text: 'TEST'
            size_hint: .1 , .1
            on_press: root.test()
            pos: 50,0

Answer 1

Your swipe method is changing the position of your widget, but your image is in the Rectangle canvas instruction. Since you haven't bound the position of that Rectangle to the position of the Widget, the image never moves. You only need to add that binding by adding pos: self.pos in the kv file as:

<Game>:
    first_image_py : first_image_kv

    Widget:
        id: first_image_kv
        pos: 0,0

        canvas.before:
            Color:
                rgb: (1,1,1)
            Rectangle:
                source: 'bg.png'
                size: self.width  , self.height
                pos: self.pos