如何使用kivy screenmanager引用其他屏幕中的对象

Question

I am trying to update a field that exists in another screen but am not succeeding. I would be very very pleased when someone could tell me what I am doing wrong here.

myscreenskv.py:

style = r'''
# File: myscreenskv.py
#: import myscreens myscreens

<ScreenManagement>:
    MainScreen:
    Screen1:
    Screen2:

<MainScreen>:
    name: 'main'
    mainlog:mainlog
    id: scrmain
    BoxLayout:
        orientation: "vertical"
        Label:
            text: "Main"
        Label:
            id: mainlog
        Button:
            text: "go to screen 1"
            on_press:
                app.root.current = "screen1"
                root.action1()
        Button:
            text: "go to screen 2"
            on_press:
                app.root.current = "screen2"
                root.action2()

<Screen1>:
    name: 'screen1'
    sc1log:sc1log
    id: scr1
    BoxLayout:
        orientation: "vertical"
        Label:
            text: "Screen1"
        Label:
            id: sc1log
        Button:
            text: "go to main screen"
            on_press: app.root.current = "main"
        Button:
            text: "go to screen 2"
            on_press: app.root.current = "screen2"

<Screen2>:
    name: 'screen2'
    id: scr2
    sc2log:sc2log
    BoxLayout:
        orientation: "vertical"
        Label:
            text: "Screen2"
        Label:
            id: sc2log
        Button:
            text: "go to main screen"
            on_press: app.root.current = "main"
        Button:
            text: "go to screen 1"
            on_press: app.root.current = "screen1"

'''

.py:

from kivy.app import App
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.lang import Builder
from myscreenskv import style

class MainScreen(Screen):
    def __init__(self, **kwargs):
        super(MainScreen, self).__init__(**kwargs)

    def action1(self):
        self.ids.scr1.sc1log.text = 'Coming from main'

    def action2(self):
        self.ids.scr2.sc2log.text = 'Coming from main'

class Screen1(Screen):
    def __init__(self, **kwargs):
        super(Screen1, self).__init__(**kwargs)

    def action1(self):
        self.ids.main.mainlog.text = 'Coming from screen1'

    def action2(self):
        self.ids.scr2.sc2log.text = 'Coming from screen1'


class Screen2(Screen):
    def __init__(self, **kwargs):
        super(Screen2, self).__init__(**kwargs)

    def action1(self):
        self.ids.main.mainlog.text = 'Coming from screen2'

    def action2(self):
        self.ids.scr1.sc1log.text = 'Coming from screen2'

class MyscreensApp(App):
    def build(self):
        Builder.load_string(style)
        sm = ScreenManager()
        sm.add_widget(MainScreen())
        sm.add_widget(Screen1())
        sm.add_widget(Screen2())
        sm.current = 'main'
        return sm


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

Answer 1

You are trying to access ids dictionary, that's nice, yet in a completely different instance, that's why this error:

AttributeError: 'super' object has no attribute '__getattr__'

You need to access the right instance, to be able to access its properties, which in your case you need to access the ScreenManager , to access its screens property (a list of instances), from which you can do the desired edits of for example text:

MainScreen.action1():

self.manager.screens[1].sc1log.text = 'Coming from main'
# no ids, because you put it into a variable before

To understand why it works let's look at the widget tree:

<MainScreen>:
    id: scrmain
    BoxLayout:
        Label:
        Label:
            id: mainlog
        Button:
        Button:

here the ids are a dictionary in MainScreen accessible from MainScreen().ids (an instance) and this is the output:

{'mainlog': <WeakProxy to <kivy.uix.label.Label object at 0x12345678>>}

which means you can't really assign the root widget to its own dictionary - at least not this way + makes no sense anyway, because you can just call root , which gives you the instance of the root widget.