Python kivy 更新 label 不同屏幕中的文本

Question

I'm working on a kivy project. I have tested the kivymd navigation layout. I wonder how can I update the label in screen 1 and screen 2. eg, count from 1 to 100 when start button is pressed.

I have searched online about kivy update label like this: update label

but the in kv string the screen is in "< >", while mine is "Screen:", and I have tried to create a function called Screen() but it is not wokring.

Can anyone please explain to me what does "< >" mean and how can I dynamically update the label in the kivymd navigation layout? thank you very much

code is here:

from kivy.lang import Builder
from kivy.uix.boxlayout import BoxLayout
from kivy.properties import ObjectProperty

from kivymd.app import MDApp

KV = '''
<ContentNavigationDrawer>:
<ItemDrawer>:
    theme_text_color: "Custom"
    on_release: self.parent.set_color_item(self)

    IconLeftWidget:
        id: icon
        icon: root.icon
        theme_text_color: "Custom"
        text_color: root.text_color


<ContentNavigationDrawer>:
    orientation: "vertical"
    padding: "8dp"
    spacing: "8dp"

    AnchorLayout:
        anchor_x: "left"
        size_hint_y: None
        height: avatar.height

        Image:
            id: avatar
            size_hint: None, None
            size: "56dp", "56dp"
            source: "data/logo/kivy-icon-256.png"

    MDLabel:
        text: "KivyMD library"
        font_style: "Button"
        size_hint_y: None
        height: self.texture_size[1]

    MDLabel:
        text: "kivydevelopment@gmail.com"
        font_style: "Caption"
        size_hint_y: None
        height: self.texture_size[1]

    ScrollView:

        MDList:

            OneLineListItem:
                text: "Screen 1"
                on_press:
                    root.nav_drawer.set_state("close")
                    root.screen_manager.current = "scr 1"

            OneLineListItem:
                text: "Screen 2"
                on_press:
                    root.nav_drawer.set_state("close")
                    root.screen_manager.current = "scr 2"


Screen:

    MDToolbar:
        id: toolbar
        pos_hint: {"top": 1}
        elevation: 10
        title: "MDNavigationDrawer"
        left_action_items: [["menu", lambda x: nav_drawer.set_state("open")]]

    NavigationLayout:
        x: toolbar.height

        ScreenManager:
            id: screen_manager

            Screen:
                name: "scr 1"

                MDLabel:
                    text: "Screen 1"
                    halign: "center"

            Screen:
                name: "scr 2"

                MDLabel:
                    text: "Screen 2"
                    halign: "center"

        MDNavigationDrawer:
            id: nav_drawer

            ContentNavigationDrawer:
                screen_manager: screen_manager
                nav_drawer: nav_drawer
'''


class ContentNavigationDrawer(BoxLayout):
    screen_manager = ObjectProperty()
    nav_drawer = ObjectProperty()


class TestNavigationDrawer(MDApp):
    def build(self):
        return Builder.load_string(KV)


TestNavigationDrawer().run()

Answer 1

You can try with app.root.get_screen('scr1').funct() and make a function to change what you want