使用.kv文件从kivy BoxLayout到ScreenManager

Question

I have an application with 1 screen in BoxLayout (filename qmscreens.py).

from kivy.app import App
from kivy.core.window import Window

class qmHome(BoxLayout):
    pass  

class qmscreensApp(App):
    def build(self):
        Window.clearcolor = (1,1,1,1)
        Window.size = (500, 500)
        homeWin = qmHome()
        return homeWin

qmscreensApp().run()

The examples below have the changes implemented as suggested.

from kivy.app import App
from kivy.core.window import Window
from kivy.uix.screenmanager import ScreenManager, Screen

class EditImage(Screen):
    pass

class QmHome(Screen):
    pass

class QManager(ScreenManager):
    elogging = BooleanProperty()

    elogging = True
    # and a lot of other python code here below


class qmscreensApp(App):
    def build(self):
        Window.clearcolor = (1,1,1,1)
        Window.size = (500, 500)
        homeWin = QManager()
        return homeWin

qmscreensApp().run()

and the following qmscreens.kv file:

QManager:
    QmHome:
    EditImage:

<QmHome>:
    name: 'home'
    Button:
        on_press: app.root.current = 'edit'
        text: 'to edit screen'
        font_size: 50

<EditImage>:
    name: 'edit'
    Button:
        on_release: app.root.current = 'home'
        text: 'back to the home screen'
        font_size: 50

    CheckBox:
        id: _evlogg_cb
        active: root.elogging

The example above gives the error message:

AttributeError: 'QmHome' object has no attribute 'elogging'

I guess the code line elogging = BooleanProperty() should be changed from the QManager to the QmHome class. But then I get other errors. So I am completely lost. Your help and directions are highly appreciated. Thanks in advance.

Answer 1

Few fixes. QManager should be the root widget and you missed a <> in the kv file

def build(self):
    Window.clearcolor = (1,1,1,1)
    Window.size = (500, 500)
    #homeWin = qmHome()
    return QManager() # <---- :)

in the kv file:

<QManager>:
    qmHome:
    EditImage:

Answer 2

Rename all occurrences of the class qmHome to QmHome . By convention across many different languages, beginning of a class should always start with a capital letter.

Kivy not recognizing the screen named with lowercase seems like a bug.