KivyMD：如何自动显示在 python 文件中生成的 MDList

Question

我是 Kivy/KivyMD/programming 的新手，我只是没有掌握 python 代码和 kv 代码之间的一些基本知识。我正在构建一个简单的应用程序，它使用 ScreenManager 在两个屏幕之间切换。在每个屏幕上，我计划有一个动态生成的列表，其中包含来自数据库的数据。我可以通过将它们放入 kv 文件来添加静态列表和其他小部件。但我似乎无法理解如何在 python 文件的类中创建/更新数据并将其链接到 kv 文件 ID。在下面的代码中，程序运行正常，我在其中放置了一个成功生成列表的按钮，但目标是没有按钮并在应用程序启动时自动生成列表。我已经对我尝试过的事情添加了一些评论。我是在使用错误的变量名还是在做一些根本错误的事情？[main.py python 文件]from kivymd.app import MDAppfrom kivy.lang import Builderfrom kivy.uix.screenmanager import ScreenManager, Screenfrom kivymd.uix.list import OneLineListItemclass FirstWindow(Screen):    print('This prints automatically when App launches')    # But adding widgets doesn't happen automatically    # I tried variations but the variable is always not defined    #self.ids.list_one.add_widget(OneLineListItem(text='List Item 1'))    #root.ids.list_one.add_widget(OneLineListItem(text='List Item 1'))    #ids.list_one.add_widget(OneLineListItem(text='List Item 1'))    # This function works when called from a button    def button_push(self):        for i in range (20):            self.ids.list_one.add_widget(OneLineListItem(text=f'List Item {i}'))class SecondWindow(Screen):    passclass WindowManager(ScreenManager):    passclass MultiscreenApp(MDApp):    def build(self):        return Builder.load_file('Multiscreen.kv')if __name__ == '__main__':    MultiscreenApp().run()[多屏.kv 文件]WindowManager:    FirstWindow:        name: 'firstwindow'    SecondWindow:        name: 'secondwindow'<FirstWindow>:    BoxLayout:        orientation: 'vertical'        MDToolbar:            title: 'SCREEN 1'        Button:            text: 'List maker button'            on_release: root.button_push()        ScrollView:            MDList:                id: list_one        MDFloatingActionButton:            elevation: 8            icon: 'plus'            pos_hint: {'center_x': .5}            on_press:                app.root.current = 'secondwindow'                root.manager.transition.direction = 'left'

Answer 1

您可以添加__init___方法来Clock.schedule_once触发列表创建。修改后的代码如下。我没有更改其余代码，只是添加了两个函数来显示自动列表创建。

from kivymd.app import MDApp

from kivy.lang import Builder

from kivy.uix.screenmanager import ScreenManager, Screen

from kivymd.uix.list import OneLineListItem

from kivy.clock import Clock

class FirstWindow(Screen):

    print('This prints automatically when App launches')

    def __init__(self, **kwargs):

        super().__init__(**kwargs)

        Clock.schedule_once(self.create_list)

        

    def create_list(self, *args):

        for i in range (20):

            self.ids.list_one.add_widget(OneLineListItem(text=f'List Item {i}'))

    # But adding widgets doesn't happen automatically

    # I tried variations but the variable is always not defined

    #self.ids.list_one.add_widget(OneLineListItem(text='List Item 1'))

    #root.ids.list_one.add_widget(OneLineListItem(text='List Item 1'))

    #ids.list_one.add_widget(OneLineListItem(text='List Item 1'))

    # This function works when called from a button

    def button_push(self):

        for i in range (20):

            self.ids.list_one.add_widget(OneLineListItem(text=f'List Item {i}'))

class SecondWindow(Screen):

    pass

class WindowManager(ScreenManager):

    pass

class MultiscreenApp(MDApp):

    def build(self):

        return Builder.load_file('Multiscreen.kv')

if __name__ == '__main__':

    MultiscreenApp().run()

Answer 2

class FirstWindow(Screen):

    def on_enter(self, *args):

        """Event fired when the screen is displayed: the entering animation is

        complete."""

        def on_enter(interval):

            for i in range (20):

                self.ids.list_one.add_widget(OneLineListItem(text=f'List Item {i}'))

        Clock.schedule_once(on_enter)