在这个网站的某个人的帮助下，我用KivyMD制作了Python按钮。这对他来说是完美的，但对我来说有些不对劲。

Question

App是用Python 3.9.5、Kivy 2.0.0rc4和KivyMD 0.104.2制作的。我做了KivyMD按钮。有了它，你可以切换暗/光模式。但这是打印错误和懒惰的原因。我是说，这对另一个帮我做事的家伙很管用。但对我不起作用。我玩了一会儿，只在这个MainWidget类上尝试切换暗/光模式。我想切换整个应用程序。这是我的Kivy代码：

<MainWidget>:

    MDScreen:
        id: screenId
        md_bg_color: 0, 0, 0, 1

    MDIconButton:
        id: light_mode
        icon: "brightness-4"
        user_font_size: "64sp"
        theme_text_color: "Custom"
        text_color: 1, 1, 1, 1
        on_press: app.presser()

这是我的Python代码：

class MainWidget(MDFloatLayout):
    pass

class MyApp(MDApp):
    pressed = False

    def build(self):
        self.theme_cls.theme_style = "Dark"
        self.screen_manager = ScreenManager()

        self.mainwidget = MainWidget()
        screen = Screen(name='First')
        screen.add_widget(self.mainwidget)
        self.screen_manager.add_widget(screen)

    def presser(self):
        if self.pressed:
            self.root.ids.light_mode.text_color = 0, 0, 0, 1
            self.root.ids.screenId.md_bg_color = 1, 1, 1, 1
            self.pressed = not self.pressed
        else:
            self.root.ids.light_mode.text_color = 1, 1, 1, 1
            self.root.ids.screenId.md_bg_color = 0, 0, 0, 1
            self.pressed = not self.pressed

这是error

 During handling of the above exception, another exception occurred:
 
 Traceback (most recent call last):
   File "C:\Users\guram\Desktop\WordBondV.2\main.py", line 815, in <module>
     myapp.run()
   File "C:\Users\guram\Desktop\WordBondV.2\venv\lib\site-packages\kivy\app.py", line 950, in run
     runTouchApp()
   File "C:\Users\guram\Desktop\WordBondV.2\venv\lib\site-packages\kivy\base.py", line 582, in runTouchApp
     EventLoop.mainloop()
   File "C:\Users\guram\Desktop\WordBondV.2\venv\lib\site-packages\kivy\base.py", line 347, in mainloop
     self.idle()
   File "C:\Users\guram\Desktop\WordBondV.2\venv\lib\site-packages\kivy\base.py", line 391, in idle
     self.dispatch_input()
   File "C:\Users\guram\Desktop\WordBondV.2\venv\lib\site-packages\kivy\base.py", line 342, in dispatch_input
     post_dispatch_input(*pop(0))
   File "C:\Users\guram\Desktop\WordBondV.2\venv\lib\site-packages\kivy\base.py", line 248, in post_dispatch_input
     listener.dispatch('on_motion', etype, me)
   File "kivy\_event.pyx", line 709, in kivy._event.EventDispatcher.dispatch
   File "C:\Users\guram\Desktop\WordBondV.2\venv\lib\site-packages\kivy\core\window\__init__.py", line 1412, in on_motion
     self.dispatch('on_touch_down', me)
   File "kivy\_event.pyx", line 709, in kivy._event.EventDispatcher.dispatch
   File "C:\Users\guram\Desktop\WordBondV.2\venv\lib\site-packages\kivy\core\window\__init__.py", line 1428, in on_touch_down
     if w.dispatch('on_touch_down', touch):
   File "kivy\_event.pyx", line 709, in kivy._event.EventDispatcher.dispatch
   File "C:\Users\guram\Desktop\WordBondV.2\venv\lib\site-packages\kivy\uix\screenmanager.py", line 1198, in on_touch_down
     return super(ScreenManager, self).on_touch_down(touch)
   File "C:\Users\guram\Desktop\WordBondV.2\venv\lib\site-packages\kivy\uix\widget.py", line 545, in on_touch_down
     if child.dispatch('on_touch_down', touch):
   File "kivy\_event.pyx", line 709, in kivy._event.EventDispatcher.dispatch
   File "C:\Users\guram\Desktop\WordBondV.2\venv\lib\site-packages\kivy\uix\relativelayout.py", line 297, in on_touch_down
     ret = super(RelativeLayout, self).on_touch_down(touch)
   File "C:\Users\guram\Desktop\WordBondV.2\venv\lib\site-packages\kivy\uix\widget.py", line 545, in on_touch_down
     if child.dispatch('on_touch_down', touch):
   File "kivy\_event.pyx", line 709, in kivy._event.EventDispatcher.dispatch
   File "C:\Users\guram\Desktop\WordBondV.2\venv\lib\site-packages\kivy\uix\widget.py", line 545, in on_touch_down
     if child.dispatch('on_touch_down', touch):
   File "kivy\_event.pyx", line 709, in kivy._event.EventDispatcher.dispatch
   File "C:\Users\guram\Desktop\WordBondV.2\venv\lib\site-packages\kivymd\uix\behaviors\ripple_behavior.py", line 255, in on_touch_down
     super().on_touch_down(touch)
   File "C:\Users\guram\Desktop\WordBondV.2\venv\lib\site-packages\kivymd\uix\button.py", line 969, in on_touch_down
     return super().on_touch_down(touch)
   File "C:\Users\guram\Desktop\WordBondV.2\venv\lib\site-packages\kivy\uix\behaviors\button.py", line 151, in on_touch_down
     self.dispatch('on_press')
   File "kivy\_event.pyx", line 705, in kivy._event.EventDispatcher.dispatch
   File "kivy\_event.pyx", line 1248, in kivy._event.EventObservers.dispatch
   File "kivy\_event.pyx", line 1132, in kivy._event.EventObservers._dispatch
   File "C:\Users\guram\Desktop\WordBondV.2\venv\lib\site-packages\kivy\lang\builder.py", line 57, in custom_callback
     exec(__kvlang__.co_value, idmap)
   File "C:\Users\guram\Desktop\WordBondV.2\my.kv", line 32, in <module>
     on_press: app.presser()
   File "C:\Users\guram\Desktop\WordBondV.2\main.py", line 810, in presser
     self.root.ids.light_mode.text_color = 1, 1, 1, 1
   File "kivy\properties.pyx", line 864, in kivy.properties.ObservableDict.__getattr__
 AttributeError: 'super' object has no attribute '__getattr__'

Answer 1

我建议将根小部件保留在kv代码中，这样您就可以在ids dict中遍历可用的id。在您的代码中，它无法找到那些id。

下面是代码的工作版本：

我已经将kivy和python代码合并到一个文件中，但是您可以使用obv。分离它们，然后使用Builder.load_file(kivy_file_name)加载您的kivy文件。

from kivymd.app import MDApp
from kivymd.uix.floatlayout import MDFloatLayout
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.lang import Builder

kv="""

ScreenManager:
    Screen:
        name: 'First'
        MainWidget:
            id: my_widget
    
<MainWidget>:

    MDScreen:
        id: screenId
        md_bg_color: 0, 0, 0, 1

    MDIconButton:
        id: light_mode
        icon: "brightness-4"
        user_font_size: "64sp"
        theme_text_color: "Custom"
        text_color: 1, 1, 1, 1
        on_press: app.presser()
"""


class MainWidget(MDFloatLayout):
    pass

class MyApp(MDApp):
    pressed = False

    def build(self):
        self.theme_cls.theme_style = "Dark"
        self.screen_manager = Builder.load_string(kv) # ScreenManager()

        #self.mainwidget = MainWidget()
        #screen = Screen(name='First')
        #screen.add_widget(self.mainwidget)
        #self.screen_manager.add_widget(screen)
        
        return self.screen_manager

    def presser(self):
        if self.pressed:
            self.root.ids.my_widget.ids.light_mode.text_color = 0, 0, 0, 1
            self.root.ids.my_widget.ids.screenId.md_bg_color = 1, 1, 1, 1
            self.pressed = not self.pressed
        else:
            self.root.ids.my_widget.ids.light_mode.text_color = 1, 1, 1, 1
            self.root.ids.my_widget.ids.screenId.md_bg_color = 0, 0, 0, 1
            self.pressed = not self.pressed


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

Answer 2

您的代码中有太多错误

别担心，我帮你解决了;)

这里是更正的代码:)

from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.properties import ObjectProperty
from kivy.lang import Builder
from kivymd.app import MDApp


kv = """
<MainWidget>:
    screenId: screenId
    light_mode: light_mode
    MDFloatLayout:        
        MDScreen:
            id: screenId
            md_bg_color: 0, 0, 0, 1

        MDIconButton:
            id: light_mode
            icon: "brightness-4"
            user_font_size: "64sp"
            theme_text_color: "Custom"
            text_color: 1, 1, 1, 1
            on_press: root.presser()
"""
Builder.load_string(kv)

sm = ScreenManager()


class MainWidget(Screen):
    pressed = False
    screenId = ObjectProperty(None)
    light_mode = ObjectProperty(None)

    def presser(self):
        if self.pressed:
            self.light_mode.text_color = 0, 0, 0, 1
            self.screenId.md_bg_color = 1, 1, 1, 1
            self.pressed = not self.pressed
        else:
            self.light_mode.text_color = 1, 1, 1, 1
            self.screenId.md_bg_color = 0, 0, 0, 1
            self.pressed = not self.pressed


class MyApp(MDApp):
    def build(self):
        self.theme_cls.theme_style = "Dark"

        sm.add_widget(MainWidget(name="First"))

        return sm


MyApp().run()

您不需要总是使用root.ids.widgetid！

您可以在您的kivy文件中将小部件定义为全局小部件，以便可以使用ObjectProperty在python文件中访问它。

此外，最佳实践是定义根类本身中属于特定类的所有方法:)