Kivy如何访问由.kv文件创建的类的实例？

Question

我的类OrderManagementScreen首先由Builder.load_文件实例化，然后由sm.add_小部件（OrderManagementScreen（name='order_management'））实例化

我希望能够访问Builder.load_文件创建的实例-我如何才能做到这一点

This post是我能找到的最接近的，但是当我执行MDApp.get_running_app（）.root时，它返回None

app.py:（在我的更新数据库功能中混合尝试）

import atexit
from kivymd.app import MDApp
from kivy.lang import Builder
from kivy.uix.screenmanager import Screen, ScreenManager
from order_management.constants import HELP_TEXT
from order_management.presentation.order_management.order_management_view import OrderManagementScreen
from order_management.presentation.components.dialog import Dialog
from order_management.data.query import Query


class App(MDApp):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        self.screen = Builder.load_file(
            "order_management/presentation/main.kv")
        self._query = Query()
        something = MDApp.get_running_app()
        self._dialog = Dialog()

    def build(self):
        self.theme_cls.primary_palette = "Green"
        sm = ScreenManager()
        # Instantiates OrderManagementScreen.py
        sm.add_widget(OrderManagementScreen(name='order_management'))
        return self.screen

    def handle_menu_click(self):
        self._dialog.render_dialog("Usage Guide:", HELP_TEXT, None, None)

    def update_database(self):
        # order_management_screen = MDApp.get_running_app().screen.children[0].manager.get_screen('order_management')
        # order_management_screen = self.screen.get_screen('order_management')
        self.order_management_screen.update_database()


if __name__ == "__main__":
    App().run()
    main_app = App()
    atexit.register(main_app.update_database)  # Calls update_database on exit.

main.kv:

#:kivy 1.11.0
#:include order_management/presentation/order_management/order_management_ui.kv
# Having to use v1.11.0 because of bug relating to MDDataTable

<Toolbar@AnchorLayout>:
    AnchorLayout:
        anchor_x: 'center'
        anchor_y: 'top'
        MDToolbar:
            title: 'Order Management App'
            specific_text_color: app.theme_cls.accent_color
            right_action_items: [['help-circle', lambda x: app.handle_menu_click()]]
            elevation: 9

ScreenManager:
    OrderManagementScreen:
        Toolbar:
 

订单管理\u ui.kv:

#:kivy 1.11.0
# Having to use v1.11.0 because of bug relating to MDDataTable

<OrderManagementScreen>:
    name: 'order_management'
    id: order_management

    GridLayout:
        cols: 1
        pos_hint: {'top': 0.85}

        ScrollView:
            id: table_container

Answer 1

我想这说明了有时候你只需要离开电脑，带着新鲜的眼睛回来

我的解决方案是在运行时简单地存储app的实例，这样当我调用update_时，数据库函数正在查看正确的实例，因此可以访问kivy创建的screen类的实例：

self.root.children[0].manager.get_screen('order_management')

我在这里使用children[0]，因为这是我添加到ScreenManager的第一个屏幕，“order_management”显然是该屏幕的名称

我希望这个偶然的机会确实能帮助其他人

新应用程序。py:

import atexit
from kivymd.app import MDApp
from kivy.lang import Builder
from kivy.uix.screenmanager import Screen, ScreenManager
from order_management.constants import HELP_TEXT
from order_management.presentation.order_management.order_management_view import OrderManagementScreen
from order_management.presentation.components.dialog import Dialog
from order_management.data.query import Query


class App(MDApp):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        self.screen = Builder.load_file(
            "order_management/presentation/main.kv")
        self._query = Query()
        self._dialog = Dialog()

    def build(self):
        self.theme_cls.primary_palette = "Green"
        sm = ScreenManager()
        sm.add_widget(OrderManagementScreen(name='order_management'))
        return self.screen

    def handle_menu_click(self):
        self._dialog.render_dialog("Usage Guide:", HELP_TEXT, None, None)

    def update_database(self):
        order_management_screen = self.root.children[0].manager.get_screen('order_management')
        order_management_screen.update_database()


if __name__ == "__main__":
    app = App()
    app.run()
    atexit.register(app.update_database)  # Calls update_database on exit.