Question

感谢您的关注。我是Kivy / KivyMD /编程的新手，在python代码和kv代码之间我根本不了解某些基本知识。

我正在构建一个使用ScreenManager在两个屏幕之间切换的简单应用程序。我计划在每个屏幕上创建一个动态生成的列表，其中包含来自数据库的数据。

我可以通过将静态列表和其他小部件放在kv文件中来添加它们。但是我似乎无法理解如何在python文件中的类中创建/更新数据并将其链接到kv文件ID。

在以下代码中，该程序正常运行，我在其中抛出了一个按钮，该按钮成功生成了一个列表，但目标是没有按钮，并在应用启动时自动生成列表。

我在尝试中添加了一些评论。我是使用错误的变量名还是做一些根本上错误的事情？

[main.py python文件]

paginate

[Multiscreen.kv文件]

from kivymd.app import MDApp
from kivy.lang import Builder
from kivy.uix.screenmanager import ScreenManager, Screen
from kivymd.uix.list import OneLineListItem


class 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):
    pass

class WindowManager(ScreenManager):
    pass

class MultiscreenApp(MDApp):
    def build(self):
        return Builder.load_file('Multiscreen.kv')

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

Answer 1

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)

Answer 2

您可以在__init___中添加Clock.schedule_once方法来触发列表的创建。修改后的代码如下。我没有更改其余代码，只是添加了两个功能来显示自动创建列表。

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()

KivyMD：如何自动显示在python文件中生成的MDList

2 个答案: