CODEWITHSUNDEEP
pythonkivy
Eka
Eka

Reputation: 15000

Changing variables from one screen to other using python in kivy

I have a two screen kivy app and I want to pass a variable from one screen to a second screen using python.

python file

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.properties import StringProperty,ObjectProperty
from kivy.uix.label import Label

class MenuScreen(Screen):
    label1=StringProperty()
    label2=StringProperty()
    def __init__(self,**kwargs):
        super(MenuScreen, self).__init__(**kwargs)  
        self.label1="hello"
        self.label2="world" 
    def change_text(self):          
        lbl1=self.label1+ " and "
        lbl2= "A beautiful "+self.label2
        chg=SettingsScreen()
        chg.UpdateSettings(lbl1,lbl2)

        # HERE: something like



class SettingsScreen(Screen):
    label3=StringProperty()
    label4=StringProperty()
    def __init__(self,**kwargs):
        super(SettingsScreen, self).__init__(**kwargs)  
        #some default texts
        self.label3="Nothing"
        self.label4="Nothing"
    def UpdateSettings(self,lbl1,lbl2):
        print(lbl1,lbl2)
        self.label3=lbl1
        self.label4=lbl2

class TestScreenManager(ScreenManager):
    menu_screen=ObjectProperty(None)
    settings_screen=ObjectProperty(None)

class TestApp(App):
    def build(self):            
        return  TestScreenManager()

TestApp().run()

kvfile

#: import ScreenManager kivy.uix.screenmanager.ScreenManager
#: import Screen kivy.uix.screenmanager.ScreenManager
#: import SettingsScreen screen


<TestScreenManager>:
    id: screen_manager
    menu_screen: menu_screen
    settings_screen: settings_screen

    MenuScreen:
        id: menu_screen
        name: 'menu'
        manager: screen_manager
    SettingsScreen:
        id: settings_screen
        name: 'settings_screen'
        manager: screen_manager


<MenuScreen>:
    name: 'MenuScreen'
    BoxLayout:
        Label:
            text:root.label1
        Label:
            text:root.label2
        Button:
            text: 'Goto nn'
            size_hint_y:0.2
            on_press: 
                root.manager.current = 'settings_screen'
                root.change_text()


<SettingsScreen>:
    #name: 'SettingsScreen'
    label_id: label_field
    BoxLayout:
        Label:
            text:root.label3
        Label:
            text:root.label4
        Label:
            id: label_field
            text: "some text"

It runs without an error but it is not changing the variables of the second screen. For debugging I added print(lbl1,lbl2) inside UpdateSetting functions and it prints out passing lbl1 and lbl2 variables but its not updating the labels.

Upvotes: 2

Views: 639

Answers (1)

FJSevilla
FJSevilla

Reputation: 4513

When you do chg=SettingsScreen(), you are creating a new instance of the SettingsScreen class and you modify the labels of that instance. You need to access the object used by your ScreenManager, not create a new one.

You can use the manager property of your current Screen to get the instance reference of the other screen:

def change_text(self):          
    lbl1=self.label1 + " and "
    lbl2= "A beautiful "+ self.label2
    chg = self.manager.settings_screen   #<<<<<<<<<<<<<<
    chg.UpdateSettings(lbl1,lbl2)

Upvotes: 2

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