Develop Reference

Return value from dropdown button in kivy

I currently have a code that runs a dropdown button in kivy. I would like to send the value 1,2,3,4 into the main class when the value is selected.
Specifying chain of events:
click dropdown button
four options are displayed
select one of the four options ==> this is when the value gets sent back to the main class
dropdown button text replaced with the selection
I have tried using get_screen(), which is equivalent to get_running_app when using windows, but this was delayed. I also tried creating an external variable but this was delayed too.
Below is my code. Thanks.
'''
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.app import App
from kivy.lang import Builder
from kivy.uix.dropdown import DropDown
class WindowManager(ScreenManager):
pass
class Drop_down(DropDown):
pass
class MenuWindow(Screen):
General_select_button_size = (100, 100)
General_select_button_pos = (400, 400)
class GeneralWindow(Screen):
drop_size = (100,100)
drop_pos = (400,400)
xax=''
def on_touch_up(self,touch):
app = self.manager.get_screen('General')
print('use get',app.ids['btn'].text)
print('use variable',self.xax)
KV = Builder.load_string("""
WindowManager:
MenuWindow:
GeneralWindow:
<MenuWIndow>:
name: 'Menu'
RelativeLayout:
Button:
allow_stretch: True
keep_ratio: True
size_hint: None,None
id: general_select_button
text: 'move to general mode'
size: root.General_select_button_size
pos: root.General_select_button_pos
on_release:
app.root.current = "General"
root.manager.transition.direction = "left"
<GeneralWindow>:
name: 'General'
RelativeLayout:
Button:
allow_stretch: True
keep_ratio: True
size_hint: None,None
id: btn
text: 'select number'
size: root.drop_size
pos: root.drop_pos
on_parent: drop_content.dismiss()
on_release:
drop_content.open(self)
root.xax=btn.text
DropDown:
id: drop_content
on_select: btn.text = '{}'.format(args[1])
Button:
id: btn1
text: '1'
size_hint_y: None
height: 30
on_release: drop_content.select('1')
Button:
id: btn2
text:'2'
size_hint_y: None
height: 30
on_release: drop_content.select('2')
Button:
id: btn3
text: '3'
size_hint_y: None
height: 30
on_release: drop_content.select('3')
Button:
id: btn4
text: '4'
size_hint_y: None
height: 30
on_release: drop_content.select('4')
""")
class ImageChangeApp(App):
def build(self):
return KV
if __name__ == '__main__':
ImageChangeApp().run()
'''

Add widget dynamically from outside class (error)

I´m learning kivy, and it has passed 3 weeks since i face this problem without encounter a solution, so i hope any of u guys could help me, i would appreciate it.
I have a main file:
from app import MyProgramApp
if __name__ == "__main__":
winapp = MyProgramApp()
winapp.run()
from where i start my app. Then i have a directory called "app", inside there is the following "init.py" file.
from kivy.app import App
from kivy.utils import QueryDict, rgba
from kivy.core.window import Window
from .view import MainWindow
Window.minimum_width = 500
Window.minimum_height = 650
Window.maximize()
class MyProgramApp(App):
colors = QueryDict()
colors.primary = rgba('#2D9CDB')
colors.secondary = rgba('#16213E')
colors.succes = rgba('#1FC98E')
colors.warning = rgba('#F2C94C')
colors.danger = rgba('#E85757')
colors.grey_dark = rgba('#C4C4C4')
colors.grey_light = rgba('#F5F5F5')
colors.black = rgba('#A1A1A1')
colors.white = rgba('#FFFFFF')
def build(self):
return MainWindow()
Same folder app, i have the following "view.py".
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.behaviors import ToggleButtonBehavior
from kivy.properties import StringProperty
from kivy.uix.screenmanager import ScreenManager
class MainWindow(BoxLayout):
username = StringProperty("Usuario")
def __init__(self, **kw):
super().__init__(**kw)
def on_press_home(self):
self.ids.scrn_mngr.current = "scrn_home"
class ViewManager(ScreenManager):
def __init__(self, **kw):
super().__init__(**kw)
class NavTab(ToggleButtonBehavior, BoxLayout):
text = StringProperty('')
icon = StringProperty('')
def __init__(self, **kw):
super().__init__(**kw)
and finally for that folder i have "myprogram.kv"
#:kivy 2.1.0
#:import Home views.home.Home
<MainWindow>:
spacing: dp(8)
canvas.before:
Color:
rgba: app.colors.white
Rectangle:
pos: self.pos
size: self.size
# NAVIGATION BAR
BoxLayout:
id: nav_menu
size_hint_x: .2
orientation: "vertical"
size_hint_min_x: dp(100)
# LOGO
BoxLayout:
id: logo_nbox
size_hint_y: .1
size_hint_min_y: dp(70)
padding: dp(16)
AnchorLayout:
anchor_x: "right"
size_hint_x: None
width: dp(52)
halign: "left"
Label:
text: "COMPANY"
halign: "center"
BoxLayout:
orientation: "vertical"
Label:
text: "COMPANY"
halign: "center"
Label:
text: "Phrase"
halign: "center"
# OPTIONS
GridLayout:
id: tabs_box
cols: 1
spacing: dp(4)
size_hint_y: .5
canvas.before:
Color:
rgba: app.colors.grey_dark
Rectangle:
pos: self.pos
size: [self.size[0], dp(1)]
NavTab:
text: "Home"
state: "down"
on_press: root.on_press_home()
# BODY
BoxLayout:
size_hint_x: .8
spacing: dp(8)
orientation: "vertical"
padding: [dp(16), dp(8), dp(12), dp(8)]
canvas.before:
Color:
rgba: app.colors.grey_light
Rectangle:
pos: self.pos
size: self.size
# SCREENS
BoxLayout:
ViewManager:
id: scrn_mngr
<ViewManager>:
Screen:
name: "scrn_home"
Home:
id: home
<NavTab>:
background_normal: ""
background_down: ""
background_color: [0,0,0,0]
group: "tabs"
size_hint_y: None
height: dp(45)
spacing: dp(4)
canvas.before:
Color:
rgba: [0,0,0,0] if self.state == "normal" else rgba("#E1F1FF")
Rectangle:
pos: self.pos
size: self.size
Color:
rgba: [0,0,0,0] if self.state == "normal" else app.colors.primary
Rectangle:
pos: [self.pos[0]+self.size[0]-dp(1), self.pos[1]]
size: [dp(8), self.size[1]]
Label:
halign: "left"
valign: "middle"
text: root.text
color: app.colors.grey_dark if root.state == "normal" else app.colors.primary
Then i got another folder called "views" inside i have another folder called "home", inside home we encounter 3 files "init.py", "home.kv", "home.py". the first one "init.py" is the following.
from .home import Home
then we got "home.kv".
#:kivy 2.1.0
<Home>:
orientation: "vertical"
Label:
size_hint_y: .1
text: "Other"
Button:
size_hint_y: .1
text: "popup"
on_press: root.open_popup()
BoxLayout:
size_hint_y: .8
id: home_box
<SomePopup>:
title: "SOME TITLE"
title_align: "center"
title_color: app.colors.primary
size_hint: .25, .8
size_hint_min_x: dp(200)
pos_hint: {"x": .1, "top": .9}
BoxLayout:
orientation: "vertical"
padding: [dp(0), dp(12), dp(0), dp(12)]
Label:
text: "Some text"
Button:
text: "create buttons on box"
on_press: root.modify_home_box()
and finally and the problem that i´m facing is whit the following file "home.py"
from kivy.lang import Builder
from kivy.uix.boxlayout import BoxLayout
from kivy.factory import Factory
from kivy.uix.popup import Popup
from kivy.uix.button import Button
from kivy.app import App
Builder.load_file('views/home/home.kv')
class Home(BoxLayout):
def __init__(self, **kwargs):
super().__init__(**kwargs)
def open_popup(self):
Factory.SomePopup().open()
class SomePopup(Popup):
def __init__(self, **kw):
super().__init__(**kw)
def modify_home_box(self):
my_app = App.get_running_app().root
my_box = my_app.ids.home.ids.home_box
custom_button = Button(
text = "something"
)
my_box.add_widget(custom_button)
That i´m trying to do is actually modify "home_box" with is store on ids Home dictionary, i also try with ObjectProperty (but that gives and Attribute Error, since i only could read propertys but doesnt modify it), instance of a new Home class doesnt work... searching for current app in App appear doesnt work since Home is store i think on screenManager...
I need add a button or some widget to "home_box" from outside class "SomePopup". I also drop here a repository on github with the whole code. github_repo
I don't know how to solve my issue, and i try with the resources available here on stack as well other net places... any help would be appreciate.

Just a very complicated path to the widget of interest. In your modify_home_box() method, try replacing:
my_app = App.get_running_app().root
my_box = my_app.ids.home.ids.home_box
with:
my_app = App.get_running_app().root
my_box = my_app.ids.scrn_mngr.ids.home.ids.home_box

KivyMD MDRectangleFlatIconButton's text is in two lines when text is updated with a long text

I want to update MDRectangleFlatIconButton's text. It changes with a new text but when the new text is longer than previous text, then the text fits in two lines.
When i use a normal button, the new text fits in one line with proper adjustment.
but Since there is a Icon in MDRectangleFlatIconButton, when a new text is longer than previous text, the text fits in a two line.
To run the program,
Add a new app name which is longer than "Info" inside "Info" button's popup window, then click "Update Top Bar's name". Then, it updated title and the text of "Info" button at the front main App.
I have tried to change this by adding button's text_size: self.width, valign:"center", haling: "center", or manually adding text_size: cm(10), cm(10).
Also, i tried with on_release: "app.root.ids.bt_information.text_size = self.width, None
but nothing works so far.
I greatly appreciate your help.
Python code
'''
from kivy.uix.widget import Widget
'''Setting the size of first window for program'''
from kivy.config import Config #another way of setting size of window
Config.set('graphics', 'width', '600') # from kivy.core.window import Window
Config.set('graphics', 'height', '750') # Window.size = ("600", "750")
from kivymd.app import MDApp
from kivy.lang import Builder
from kivy.factory import Factory
from kivy.uix.popup import Popup
from kivy.properties import ObjectProperty
Builder.load_file('new_window_popup.kv')
class Dex(Popup):
pass
class Remi(Popup):
pass
class Info(Popup):
pass
class MyLayout(Widget):
pass
class AwesomeApp(MDApp):
def build(self):
self.title = "My house"
return MyLayout()
if __name__ == '__main__':
AwesomeApp().run()
'''
kivyfile: new_window_popup.kv
'''
#:import Factory kivy.factory.Factory
#:import MDRaisedButton kivymd.uix.button
<Dex>:
auto_dismiss: False
size_hint: 1, 1
title: "Weight-Based Dose Calculator "
canvas.before:
Color:
rgba: (0,1,0,1)
Rectangle:
pos:self.pos
size:self.size
BoxLayout:
orientation: "vertical"
size:root.width, root.height
Label:
text: "Dex 1"
Button:
text: "Close"
font_size: 24
on_release: root.dismiss()
<Remi>:
auto_dismiss: False
size_hint: 1, 1
title: "Weight-Based Dose Calculator "
canvas.before:
Color:
rgba: (0,1,0,1)
Rectangle:
pos:self.pos
size:self.size
BoxLayout:
orientation: "vertical"
size:root.width, root.height
Label:
text: "Remi"
Button:
text: "Close"
font_size: 24
on_release: root.dismiss()
<Info>:
appName:appName
auto_dismiss: False
size_hint: 1, 1
title: "Change Info"
canvas.before:
Color:
rgba: (0,1,0,1)
Rectangle:
pos:self.pos
size:self.size
BoxLayout:
orientation: "vertical"
size:root.width, root.height
Label:
text: "What is your App name?"
BoxLayout:
orientation: "horizontal"
MDTextField:
id: appName
hint_text: "App Name"
color_mode: 'primary'
current_hint_text_color: 1,1,1,1
hint_text_color_focus: 1,1,1,.9
line_color_focus: 1,1,1,1
font_size: '25sp'
text_color_normal: 1,1,1,.9
text_color_focus: 0,0,1,.9
focus: True
write_tab: False
Button:
text: "Update Top Bar\'s name"
font_size: 24
size_hint: .8, .2
# on_release: root.updateName()
on_release:
app.title = appName.text
app.root.ids.bt_information.text = appName.text
Button:
text: "Close"
font_size: 24
on_release: root.dismiss()
<MyLayout>
MDBoxLayout:
orientation:"vertical"
size: root.width, root.height
MDRaisedButton:
text: "Dex"
font_size: 32
text_color: 0,0,0,.9
size_hint: 1,.5
on_press: Factory.Dex().open()
MDRaisedButton:
text: "Remi"
font_size: 32
size_hint: 1,.5
on_press: Factory.Remi().open()
MDRectangleFlatIconButton:
id: bt_information
text: "Info"
icon: "youtube-studio"
font_size: 32
size_hint: 1,.2
text_size: self.width, None
md_bg_color: 0.95,0.61,0.73,1
on_press: Factory.Info().open()
'''

Kivy FileChooser Overlapping

I am using the FileChooserListView from kivy and have run into a overlapping text on scroll with screens that another user came across as well. I looked through their post on GitHub and read that some people are using the plyer FileChooser. I also saw that someone mentioned that it has to do with the Building function of the .kv file. I created a new kivy app and the problem did not occur, but when I return to my older app (no changes of any kind) the problem still occurs.
Sorry for the long post, but I am unsure how these two kivy app codes are different. Am I calling something twice that is causing the FileChooser to "hold" it's position? I am not oppose to using plyer's FileChooser, but could someone give me an example on how to implement it?
testing_kivy.py
from kivy.app import App
from kivy.lang.builder import Builder
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.uix.popup import Popup
from kivy.properties import ObjectProperty
from kivy.uix.floatlayout import FloatLayout
import os
def train_load(path, filename):
download_path = os.path.join(path, filename[0])
print(download_path)
class LoadDialog(FloatLayout):
load = ObjectProperty(None)
cancel = ObjectProperty(None)
class TrainingWindow(Screen):
def show_load_list(self):
content = LoadDialog(load=train_load, cancel=self.dismiss_popup)
self._popup = Popup(title="Load a file list", content=content, size_hint=(1, 1))
self._popup.open()
def dismiss_popup(self):
self._popup.dismiss()
class WindowManager(ScreenManager):
pass
kv_training = Builder.load_file('testing_kivy.kv')
class MyApp(App):
def build(self):
return kv_training
if __name__ == '__main__':
MyApp().run()
testing_kivy.kv
WindowManager:
TrainingWindow:
<TrainingWindow>
name: "training"
BoxLayout:
orientation: "vertical"
Button:
text: "Select Training Images"
font_size: 32
on_release: root.show_load_list()
Button:
text: "Select Training Annots"
font_size: 32
on_release: root.show_load_list()
Button:
text: "Set Parameters"
font_size: 32
on_release:
app.root.current = "parameters_train"
root.manager.transition.direction = "up"
Button:
text: "Back"
font_size: 16
on_release:
app.root.current = "select"
root.manager.transition.direction = "right"
<LoadDialog>:
BoxLayout:
size: root.size
pos: root.pos
orientation: "vertical"
FileChooserListView:
id: filechooser
BoxLayout:
size_hint_y: None
height: 30
Button:
text: "Cancel"
on_release: root.cancel()
Button:
text: "Load"
on_release: root.load(filechooser.path, filechooser.selection)
Older_app.py
from kivy.app import App
from kivy.lang.builder import Builder
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.uix.popup import Popup
from kivy.uix.button import Button
from kivy.uix.boxlayout import BoxLayout
from kivy.properties import ObjectProperty
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.spinner import SpinnerOption
import os
import pandas as pd
def invalid_login():
app = App.get_running_app()
app.root.current = "main"
# Create a BoxLayout to add multiple lines or buttons to a PopUp
box = BoxLayout()
# Create PopUp
pop = Popup(
title="Invalid Password",
size_hint=(None, None), size=(200, 100),
content=box,
auto_dismiss=False
)
# Dismiss PopUp
box.add_widget(Button(text="Close", on_release=pop.dismiss))
pop.open()
def model_load(path, filename):
download_path = os.path.join(path, filename[0])
print(download_path)
def train_load(path, filename):
download_path = os.path.join(path, filename[0])
print(download_path)
def train_model_load(path, filename):
download_path = os.path.join(path, filename[0])
print(download_path)
class MainWindow(Screen):
def login(self):
if self.ids.password.text == "password":
self.ids.password.text = ""
app = App.get_running_app()
app.root.current = "select"
else:
self.ids.password.text = ""
invalid_login()
class SelectWindow(Screen):
pass
class LoadDialog(FloatLayout):
load = ObjectProperty(None)
cancel = ObjectProperty(None)
class TrainingWindow(Screen):
def show_load_list(self):
content = LoadDialog(load=train_load, cancel=self.dismiss_popup)
self._popup = Popup(title="Load a file list", content=content, size_hint=(1, 1))
self._popup.open()
def dismiss_popup(self):
self._popup.dismiss()
class ModelWindow(Screen):
def show_load_list(self):
content = LoadDialog(load=model_load, cancel=self.dismiss_popup)
self._popup = Popup(title="Load a file list", content=content, size_hint=(1, 1))
self._popup.open()
def dismiss_popup(self):
self._popup.dismiss()
class TrainModelWindow(Screen):
def show_load_list(self):
content = LoadDialog(load=train_model_load, cancel=self.dismiss_popup)
self._popup = Popup(title="Load a file list", content=content, size_hint=(1, 1))
self._popup.open()
def dismiss_popup(self):
self._popup.dismiss()
class ParametersTrainModelWindow(Screen):
pass
class ParametersTrainWindow(Screen):
pass
class WindowManager(ScreenManager):
pass
class OverViewTrainWindow(Screen):
pass
class OverViewTrainModelWindow(Screen):
pass
class OverViewModelWindow(Screen):
pass
class MyOption(SpinnerOption):
pass
kv_main= Builder.load_file('main.kv')
class MyApp(App):
def build(self):
return kv_main
if __name__ == '__main__':
MyApp().run()
main.kv
#:import utils kivy.utils
#:include select.kv
#:include training.kv
#:include model.kv
#:include train_model.kv
#:include parameters_train.kv
#:include parameters_train_model.kv
#:include overview_train_model.kv
#:include overview_train.kv
#:include overview_model.kv
WindowManager:
MainWindow:
SelectWindow:
TrainingWindow:
ModelWindow:
TrainModelWindow:
ParametersTrainWindow:
ParametersTrainModelWindow
OverViewTrainWindow:
OverViewTrainModelWindow:
OverViewModelWindow:
<MainWindow>
name: "main"
GridLayout:
cols: 1
BoxLayout:
orientation: "vertical"
canvas.before:
Color:
rgba: 0,0,0,1
Rectangle:
pos: self.pos
size: self.size
Label:
size_hint: 1, 1
text: "SPECPHASE"
font_size: 50
color:
utils.get_color_from_hex('#FF0000')
Label:
size_hint: 1, 1
text: "Object Detection App"
font_size: 40
BoxLayout:
size_hint: 1, 0.005
canvas.before:
Color:
rgba: (1,1,1,1)
Rectangle:
size: self.size
pos: self.pos
BoxLayout:
orientation: "horizontal"
size_hint: (0.35, 0.35)
padding: (0,0,25,0)
Label:
font_size: 20
text: "Password"
size_hint: (0.5, 0.35)
pos_hint: {'x': 1, 'y': 0.4}
background_color: (0,0,0,1)
canvas.before:
Color:
rgba: self.background_color
Rectangle:
size: self.size
pos: self.pos
TextInput:
id: password
multiline: False
size_hint: (0.5, 0.35)
pos_hint: {'x': 1, 'y': 0.4}
focus: True
background_color:
utils.get_color_from_hex('#18B8D9')
cursor_color: (0,0,0,1)
password: True
Button:
text: "Submit"
on_release: root.login()
select.kv
<SelectWindow#Screen>:
name: "select"
GridLayout:
cols: 1
GridLayout:
cols: 2
Button:
text: "Train"
font_size: 32
on_release:
app.root.current = "training"
root.manager.transition.direction = "right"
Button:
text: "Model"
font_size: 32
on_release:
app.root.current = "model"
root.manager.transition.direction = "left"
Button:
text: "Train & Model"
font_size: 32
on_release:
app.root.current = "train_model"
root.manager.transition.direction = "up"
training.kv
<TrainingWindow#Screen>:
name: "training"
BoxLayout:
orientation: "vertical"
Button:
text: "Select Training Images"
font_size: 32
on_release: root.show_load_list()
Button:
text: "Select Training Annots"
font_size: 32
on_release: root.show_load_list()
Button:
text: "Set Parameters"
font_size: 32
on_release:
app.root.current = "parameters_train"
root.manager.transition.direction = "up"
Button:
text: "Back"
font_size: 16
on_release:
app.root.current = "select"
root.manager.transition.direction = "right"
<LoadDialog>:
BoxLayout:
size: root.size
pos: root.pos
orientation: "vertical"
FileChooserListView:
id: filechooser
BoxLayout:
size_hint_y: None
height: 30
Button:
text: "Cancel"
on_release: root.cancel()
Button:
text: "Load"
on_release: root.load(filechooser.path, filechooser.selection)

After taking a break from this for while and restarting my brain, I was able to find the problem.
Not included in my question, I have a couple more .kv files that have a similar layout to the training.kv. They are used to access other screens. I found that I was calling FileChooserListView in each screen and I belive that is why I was seeing the stacking problem. I ended up removing all of them except for the one in my training.kv file and all is working.

Kivy: changing image source on screen

After much headbanging, I've created an app that opens the FileChooser and picks an image. A function will then transform the image and change it on the screen.
< FirstScreen > is just something to start with, relatively unimportant.
< SecondScreen > is the file chooser. The path may need editing. < ThirdScreen > shoudl show the image along with buttons that will eventually lead elsewhere.
I suspect the problem is that the line
sm.current = "_third_screen_"
is creating a new instance separate to everything else I've passed items too. How do I show the image I selected?
from kivy.lang import Builder
from kivy.app import App
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.properties import ObjectProperty, StringProperty
Builder.load_string("""
<MyScreenManager>:
FirstScreen:
SecondScreen:
ThirdScreen:
<FirstScreen>:
name: '_first_screen_'
BoxLayout:
orientation: "horizontal"
Label:
id: first_screen_label
text: "Hi, I'm the home page"
BoxLayout:
orientation: "vertical"
Button:
text: "Okay!"
on_press: root.manager.current = '_second_screen_'
Button:
text: "Cancel!"
on_press: app.stop()
<SecondScreen>:
name: '_second_screen_'
id: file_chooser
BoxLayout:
id: file_chooser_box_layout
orientation: "horizontal"
Button
text: "Open"
on_press:
root.callback_image_and_other_stuff(file_chooser_list_view.selection)
FileChooserListView:
id: file_chooser_list_view
<ThirdScreen>:
name: '_third_screen_'
BoxLayout:
orientation: "vertical"
id: third_screen
Label:
id: main_title
text: "Upload"
size_hint: (1, 0.1)
Image:
id: main_image
source: root.img
size_hint: (1, 0.75)
BoxLayout:
orientation: "horizontal"
padding: 10
size_hint: (1, 0.15)
Button:
text: "Okay"
size_hint: (0.5, 1)
on_press: image_viewer.image_accepted_by_user(filechooser.selection)
Button:
text: "Cancel"
size_hint: (0.5, 1)
on_press: root.manager.current = '_first_screen_'
""")
class FirstScreen(Screen):
pass
class SecondScreen(Screen):
def callback_image_and_other_stuff(self, new_image_address):
# do other stuff here also, then pass new_image_address along
new_image_address = new_image_address[0].replace("\\", "/")
third_screen = ThirdScreen()
third_screen.callback_image(new_image_address)
class ThirdScreen(Screen):
img = ObjectProperty(None)
def __init__(self, **kwargs):
super(Screen, self).__init__(**kwargs)
def callback_image(self, new_image_address):
sm.current = "_third_screen_"
self.img = new_image_address
self.ids.main_image.source = self.img
print(self.img)
# Create the screen manager
sm = ScreenManager() # Problem?
sm.add_widget(FirstScreen(name='_first_screen_'))
sm.add_widget(SecondScreen(name='_second_screen_'))
sm.add_widget(ThirdScreen(name='_third_screen_'))
class MyApp(App):
def build(self):
return sm
if __name__ == '__main__':
MyApp().run()

Every time you use some_obj = SomClass() you are creating a new object, in your case that is what you are doing, you are creating a new ThirdScreen different from the one shown by that you do not observe the image, the solution is that you have to access to the initial object using the ScreenManager and name screen.
from kivy.lang import Builder
from kivy.app import App
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.properties import ObjectProperty, StringProperty
Builder.load_string("""
<FirstScreen>:
BoxLayout:
orientation: "horizontal"
Label:
id: first_screen_label
text: "Hi, I'm the home page"
BoxLayout:
orientation: "vertical"
Button:
text: "Okay!"
on_press: root.manager.current = '_second_screen_'
Button:
text: "Cancel!"
on_press: app.stop()
<SecondScreen>:
id: file_chooser
BoxLayout:
id: file_chooser_box_layout
orientation: "horizontal"
Button
text: "Open"
on_press:
root.callback_image_and_other_stuff(file_chooser_list_view.selection)
FileChooserListView:
id: file_chooser_list_view
<ThirdScreen>:
BoxLayout:
orientation: "vertical"
id: third_screen
Label:
id: main_title
text: "Upload"
size_hint: (1, 0.1)
Image:
id: main_image
source: root.img
size_hint: (1, 0.75)
BoxLayout:
orientation: "horizontal"
padding: 10
size_hint: (1, 0.15)
Button:
text: "Okay"
size_hint: (0.5, 1)
on_press: image_viewer.image_accepted_by_user(filechooser.selection)
Button:
text: "Cancel"
size_hint: (0.5, 1)
on_press: root.manager.current = '_first_screen_'
""")
class FirstScreen(Screen):
pass
class SecondScreen(Screen):
def callback_image_and_other_stuff(self, new_image_address):
if new_image_address:
third_screen = self.manager.get_screen("_third_screen_")
# do other stuff here also, then pass new_image_address along
new_image_address = new_image_address[0].replace("\\", "/")
third_screen.callback_image(new_image_address)
class ThirdScreen(Screen):
img = ObjectProperty(None)
def __init__(self, **kwargs):
super(Screen, self).__init__(**kwargs)
def callback_image(self, new_image_address):
sm.current = "_third_screen_"
self.img = new_image_address
self.ids.main_image.source = self.img
print(self.img)
# Create the screen manager
sm = ScreenManager() # Problem?
sm.add_widget(FirstScreen(name='_first_screen_'))
sm.add_widget(SecondScreen(name='_second_screen_'))
sm.add_widget(ThirdScreen(name='_third_screen_'))
class MyApp(App):
def build(self):
return sm
if __name__ == '__main__':
MyApp().run()