如何在两个屏幕之间保持相同的 label 文本 kivy

Question

I'm new to kivy and python so my code isn't perfect. I'm trying to make a program with 2 screens, a first screen where there is a label with a text that is not defined and that can change and a second screen that keeps the same text as the first screen.

I've been searching for a week and I tried to make a global variable that I edit and that becomes the text of the second label but it doesn't work.

I also tried with String. property () or object. property () but I didn't get any more results and I didn't really understand how to use it.

Any help would be welcome <3

(sorry for my english)

Here is a part of my code that I have simplified as much as possible:

from kivy.app import App
from kivy.uix.button import Button
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.label import Label
from kivy.core.window import Window
from kivy.lang import Builder
from kivy.uix.screenmanager import ScreenManager, Screen


Builder.load_string("""

<MenuScreen>:
    label_wid : ratio
    FloatLayout:         
        Button:
            text: "options"
            pos: 270, 240
            size_hint: .30, .10
            background_color: 0,1,0,0.75
            on_press: root.manager.current = 'settings'
         Label:
            id:ratio
            text: ""
            pos: 0,90
            font_size:30
            color:1,0,0,1


<SettingsScreen>:
    label_wid2 : ratio
    FloatLayout:
        Label:
            id:ratio
            text: str(root.texte2())
            pos: 0,90
            font_size:30
            color:1,0,0,1

""")

u=""

class MenuScreen(Screen):

    def texte(self):
        global u
        u= self.label_wid.text = 'exemple' 
    pass

class SettingsScreen(Screen):

    def texte2(self):
        self.label_wid2.text=u


    pass


class Quizz(App):
    def build(self):
        self.title = 'Quizz'
        Window.clearcolor = (0, 1, 1, 0.25)
        return sm


sm = ScreenManager()
sm.add_widget(MenuScreen(name='menu'))
sm.add_widget(SettingsScreen(name='settings'))


if __name__ == '__main__':
    Quizz().run()
from kivy.app import App
from kivy.uix.button import Button
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.label import Label
from kivy.core.window import Window
from kivy.lang import Builder
from kivy.uix.screenmanager import ScreenManager, Screen


Builder.load_string("""

<MenuScreen>:
    label_wid : ratio
    FloatLayout:         
        Button:
            text: "options"
            pos: 270, 240
            size_hint: .30, .10
            background_color: 0,1,0,0.75
            on_press: root.manager.current = 'settings'
         Label:
            id:ratio
            text: ""
            pos: 0,90
            font_size:30
            color:1,0,0,1


<SettingsScreen>:
    label_wid : ratio
    FloatLayout:
        Label:
            id:ratio
            text: root.texte2()
            pos: 0,90
            font_size:30
            color:1,0,0,1

""")

u=""

class MenuScreen(Screen):

    def texte(self):
        global u
        u= self.label_wid.text = 'exemple' 
    pass

class SettingsScreen(Screen):

    def texte2(self, text):
        u


    pass


class Quizz(App):
    def build(self):
        self.title = 'Quizz'
        Window.clearcolor = (0, 1, 1, 0.25)
        return sm


sm = ScreenManager()
sm.add_widget(MenuScreen(name='menu'))
sm.add_widget(SettingsScreen(name='settings'))


if __name__ == '__main__':
    Quizz().run() ```

Answer 1

Using a StringProperty in the ScreenManager and another in SettingsScreen provide a source of text for both Labels in the different Screens . And changing the StringProperty can change both Labels :

from kivy.app import App
from kivy.clock import Clock
from kivy.properties import StringProperty
from kivy.core.window import Window
from kivy.lang import Builder
from kivy.uix.screenmanager import ScreenManager, Screen


class MenuScreen(Screen):
    pass


class SettingsScreen(Screen):
    # this is the text to be used when the first Label text is not '1'
    theOtherText = StringProperty('Not One')


class MyScreenManager(ScreenManager):
    # This is the text that both Labels may display
    theText = StringProperty('0')


kv = """
MyScreenManager:
    MenuScreen:
        name: 'menu'
    SettingsScreen:
        name: 'settings'

<MenuScreen>:
    label_wid : ratio
    FloatLayout:         
        Button:
            text: "options"
            pos: 270, 240
            size_hint: .30, .10
            background_color: 0,1,0,0.75
            on_press: root.manager.current = 'settings'
        Label:
            id:ratio
            # Use theText Property from MyScreenManager
            text: root.manager.theText
            pos: 0,90
            font_size:30
            color:1,0,0,1

<SettingsScreen>:
    label_wid : ratio
    FloatLayout:
        Label:
            id:ratio
            # Use theText Property from MyScreenManager
            text: '1' if root.manager.theText == '1' else root.theOtherText
            pos: 0,90
            font_size:30
            color:1,0,0,1

"""


class Quizz(App):
    def build(self):
        self.title = 'Quizz'
        Window.clearcolor = (0, 1, 1, 0.25)
        Clock.schedule_once(self.change_text, 4)
        return Builder.load_string(kv)

    def change_text(self, dt):
        print('changing text')
        self.root.theText = '1'


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

Building the MyScreenManager in the kv eliminates the need to check if the manager attribute of the Screens is set. That simplifies the logic in the kv . Then the line in kv :

text: '1' if root.manager.theText == '1' else root.theOtherText

sets the text of the second Label to 1 if the first Label text is 1 , otherwise it is set to the value of theOtherText in the SettingsScreen .

I have added a Clock.schedule_once() just for testing.