我在利用Kivy和Kivymd。 在类admin和类editarticle之间传递变量时遇到问题。 我需要将my_string从Admin传递到editarticle。 我正在尝试这样做，但得到一个空字符串。 因此，在类admin中，我有my_string。 然后，在class admin的方法edit_article中，我正在为my_string设置值'some text'。 然后我尝试在类EditArticle的方法edit中获取它。 但它一直都是空的。 我真的想不通。

1. 如果运行我的代码，您将单击顶部菜单admin。
2. 然后单击任何mdchip。
3. 然后单击对话框窗口中的“etit”按钮。
4. 然后单击按钮获取My_String（但它始终为空）。

这是我的app.py

from kivy.clock import Clock
from kivymd.app import MDApp
from kivy.properties import StringProperty, NumericProperty
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.uix.boxlayout import BoxLayout
from kivymd.uix.card import MDCard
from kivymd.uix.chip import MDChip
from kivy.core.window import Window
Window.size = (600, 853)
from kivymd.uix.menu import MDDropdownMenu
from kivymd.theming import ThemableBehavior
from kivymd.uix.behaviors import RectangularElevationBehavior
from kivymd.uix.boxlayout import MDBoxLayout
from kivymd.uix.button import MDFlatButton
from kivymd.uix.dialog import MDDialog

class WindowManager(ScreenManager):
    pass

class AdminFooter(ThemableBehavior, RectangularElevationBehavior, MDBoxLayout):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        self.md_bg_color = self.theme_cls.primary_color

class ToolbarBack(ThemableBehavior, RectangularElevationBehavior, MDBoxLayout):
    pass

class CustomToolbar(ThemableBehavior, RectangularElevationBehavior, MDBoxLayout):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        self.md_bg_color = self.theme_cls.primary_color

        Clock.schedule_once(self.create_menu, 1)

    def create_menu(self, i):
        self.items = ['admin', 'settings']
        menu_items = [{"text":  f"{i}"} for i in self.items]
        self.menu = MDDropdownMenu(
            caller=self.ids.button_2, items=menu_items, width_mult=4, callback=self.get_item
        )

    def get_item(self, instance):
        self.menu.dismiss()
        App.get_running_app().window_manager.current = instance.text

class Content(BoxLayout):
    pass

class Admin(Screen):

    dialog_get_article = None

    my_string = StringProperty() # My string

    def __init__(self, **kwargs):
        super().__init__(**kwargs)

    def get_article(self, instance, 
        self.dialog_get_article = MDDialog(
            title="Click the EDIT",
            buttons=[
                MDFlatButton(
                    text="EDIT",
                    on_release = self.edit_article
                ),
            ],
        )
        self.dialog_get_article.open()

    def edit_article(self, instance):
        self.my_string = 'some text' # set value
        App.get_running_app().window_manager.current = 'edit-article'
        self.dialog_get_article.dismiss()

    def on_enter(self, *args):
        data = [
            {'id': 1, 'title': 'Arcicle 1', 'body': 'body of Article 1'},
            {'id': 2, 'title': 'Arcicle 2', 'body': 'body of Article 2'},
            {'id': 3, 'title': 'Arcicle 3', 'body': 'body of Article 3'}
        ]
        for x in data:
            chip = BlogChip(id=x.get('id'), title=x.get('title'), body=x.get('body'))
            self.ids.box.add_widget(chip)

class EditArticle(Screen):

    var = StringProperty()

    def edit(self, instance):
        print(self.var, ' << it is goingt to be <my_string> from Admin')

class UserSettings(Screen):
    pass

class BlogChip(MDChip):

    get_admin = Admin()

    id = NumericProperty()
    title = StringProperty()
    body = StringProperty()

class BlogCard(MDCard):
    pass

class Detail(Screen):
    pass

class ResultSearch(Screen):
    pass

class Container(Screen):

    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        Clock.schedule_once(self.create_cards)

    def create_cards(self, i):
        pass

class App(MDApp):

    def callback(self):
        self.window_manager.current = 'container'

    def build(self):
        self.theme_cls.primary_palette = 'Indigo'
        self.window_manager = WindowManager()
        return self.window_manager

App().run()

我的应用程序kV

 <WindowManager>
    Container:
        id: scr_1
        name: 'container'
    Detail:
        id: scr_2
        name: 'detail'

    Admin:
        id: scr_3
        name: 'admin'
    EditArticle:
        id: scr_4
        name: 'edit-article'
        var: scr_3.my_string # <---------

    ResultSearch:
        id: scr_5
        name: 'result-search'
    UserSettings:
        id: scr_6
        name: 'settings'

<Admin>:
    BoxLayout:
        id: boxlayout_1
        orientation: 'vertical'

        MDToolbar:
            pos_hint: {'top': 1}
            title: 'Admin Blog'
            left_action_items: [["arrow-left", lambda x: app.callback()]]

        ScrollView:
            MDStackLayout:
                adaptive_height: True
                padding: 10
                spacing: dp(5)
                id: box

<EditArticle>
    MDToolbar:
        title: 'Admin Blog'
    MDLabel:
        text: str(root.var)
    MDRaisedButton:
        text: 'click me to see a variable in console'
        pos_hint: {'center_x': .5, 'center_y': .5}
        on_release: root.edit(root)

<MyToolbar@CustomToolbar>:
    size_hint_y: None
    height: self.theme_cls.standard_increment
    padding: "25dp"
    spacing: "12dp"

    MDLabel:
        id: label
        text: 'Blog'
        font_style: 'H6'
        theme_text_color: "Custom"
        text_color: 1,1,1,1

    Widget:

    MDIconButton:
        id: button_2
        icon: "dots-vertical"
        pos_hint: {"center_y": .5}
        theme_text_color: "Custom"
        text_color: 1,1,1,1
        on_release: root.menu.open()

<Container>
    BoxLayout:
        orientation: 'vertical'
        MyToolbar:
        MDLabel:
            text: 'Go To menu (dot-vertical/admin'
            halign: 'center'

<BlogCard>

<Detail>:

<BlogChip>
    label: root.title
    icon: ''
    callback: root.get_admin.get_article