问题

I got a problem with my kv code here. I want to create a MDNavigationDrawer with a few NavigationDrawerIconButtons. The window shows up but when I click at the MDToolbar the program crashes and shows this Error Message.

 Traceback (most recent call last):
   File "C:/Users/path/to/my/file/main.py", line 189, in <module>
     KivyGUI().run()
   File "C:\Users\uname\Anaconda3\lib\site-packages\kivy\app.py", line 855, in run
     runTouchApp()
   File "C:\Users\uname\Anaconda3\lib\site-packages\kivy\base.py", line 504, in runTouchApp
     EventLoop.window.mainloop()
   File "C:\Users\uname\Anaconda3\lib\site-packages\kivy\core\window\window_sdl2.py", line 746, in mainloop
     self._mainloop()
   File "C:\Users\uname\Anaconda3\lib\site-packages\kivy\core\window\window_sdl2.py", line 478, in _mainloop
     EventLoop.idle()
   File "C:\Users\uname\Anaconda3\lib\site-packages\kivy\base.py", line 342, in idle
     self.dispatch_input()
   File "C:\Users\uname\Anaconda3\lib\site-packages\kivy\base.py", line 327, in dispatch_input
     post_dispatch_input(*pop(0))
   File "C:\Users\uname\Anaconda3\lib\site-packages\kivy\base.py", line 293, in post_dispatch_input
     wid.dispatch('on_touch_up', me)
   File "kivy\_event.pyx", line 707, in kivy._event.EventDispatcher.dispatch
   File "C:\Users\uname\Anaconda3\lib\site-packages\kivymd\ripplebehavior.py", line 84, in on_touch_up
     return super().on_touch_up(touch)
   File "C:\Users\uname\Anaconda3\lib\site-packages\kivymd\button.py", line 480, in on_touch_up
     return super().on_touch_up(touch)
   File "C:\Users\uname\Anaconda3\lib\site-packages\kivy\uix\behaviors\button.py", line 179, in on_touch_up
     self.dispatch('on_release')
   File "kivy\_event.pyx", line 703, in kivy._event.EventDispatcher.dispatch
   File "kivy\_event.pyx", line 1214, in kivy._event.EventObservers.dispatch
   File "kivy\_event.pyx", line 1138, in kivy._event.EventObservers._dispatch
   File "C:\Users\path\to\my\file\design.kv", line 59, in <lambda>
     left_action_items: [['dots-vertical', lambda x: root.toggle_nav_drawer()]]
   File "kivy\weakproxy.pyx", line 32, in kivy.weakproxy.WeakProxy.__getattr__
 AttributeError: 'LayoutPy' object has no attribute 'toggle_nav_drawer'

I import the kv code from a separate file.

#:kivy 1.11.0
#:import MDNavigationDrawer kivymd.navigationdrawer.MDNavigationDrawer
#:import NavigationLayout kivymd.navigationdrawer.NavigationLayout
#:import NavigationDrawerDivider kivymd.navigationdrawer.NavigationDrawerDivider
#:import NavigationDrawerToolbar kivymd.navigationdrawer.NavigationDrawerToolbar
#:import NavigationDrawerSubheader kivymd.navigationdrawer.NavigationDrawerSubheader
#:import MDToolbar kivymd.toolbar.MDToolbar

<ContentNavigationDrawer@MDNavigationDrawer>:
    drawer_logo: 'src/LinguIcon.png'

    NavigationDrawerSubheader:
        text: "Menu:"

<LayoutPy>:
    orientation: 'vertical'
    scr_mngr: scr_mngr

    NavigationLayout:
        id: nav_layout

        ContentNavigationDrawer:
            id: nav_drawer
            name: 'nav_drawer'

            NavigationDrawerToolbar:
                title: 'Options'

            NavigationDrawerIconButton:
                icon: 'settings'
                text: 'Select Language'
                on_release: root.open2ndScreen('screen_card')

            NavigationDrawerIconButton:
                icon: 'close'
                text: 'Exit'
                on_release: root.exit()

            NavigationDrawerIconButton:
                icon: 'face'
                text: 'Contact the developer'
                on_release: root.sendDevHint()

        BoxLayout:
            orientation: 'vertical'

            MDToolbar:
                id: toolbar
                title: 'Menu'
                md_bg_color: app.theme_cls.primary_color
                background_palette: 'Primary'
                background_hue: '500'
                left_action_items: [['dots-vertical', lambda x: root.toggle_nav_drawer()]]

            Widget:

    ScreenManager:
        id: scr_mngr
        screen_main: screen_main

        Screen:
            id: screen_main
            name: 'screen_main'
            input_words: input_words
            lbl: lbl
            btn: btn

            FloatLayout:

                ### A few widgets ### 

        Screen:
            id: screen_card
            name: 'screen_card'

            FloatLayout:

                ### A few widgets ###

The Python code:

import sys
import kivy
from kivy.app import App
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.boxlayout import BoxLayout
from kivy.core.window import Window
from kivymd.theming import ThemeManager
from kivymd.label import MDLabel
from kivymd.textfields import MDTextField, MDTextFieldClear, MDTextFieldRect, MDTextFieldRound
from kivy.lang import Builder
from kivymd.navigationdrawer import MDNavigationDrawer, NavigationDrawerIconButton, NavigationLayout
from kivy.properties import ObjectProperty
from kivymd.toast import toast

kivy.require('1.11.0')

class LayoutPy(FloatLayout):
    def __init__(self, **kwargs):
        super(LayoutPy, self).__init__(**kwargs)
        self.scr_mngr = ObjectProperty(None)
        self.build_nav_btns()

    def callback(self, instance, value):
        toast("Pressed item menu %d" % value)

    def exit(self):
        sys.exit(1)

    def build_nav_btns(self):
        btns = ["Select Language", "Contact the developer", "Exit"]
        for count, btn in enumerate(btns):
            if count == 1:
                self.ids.nav_drawer.add_widget(
                NavigationDrawerIconButton(
                    icon='settings', text=btn,
                    on_release=lambda x, btn: self.callback(x, btn)))
            elif count == 2:
                self.ids.nav_drawer.add_widget(
                NavigationDrawerIconButton(
                    icon='face', text=btn,
                    on_release=lambda x, btn: self.callback(x, btn)))
            elif count == 3:
                self.ids.nav_drawer.add_widget(
                NavigationDrawerIconButton(
                    icon='close', text=btn,
                    on_release=lambda x: self.exit()))

Builder.load_file("design.kv")

class KivyGUI(App):
    theme_cls = ThemeManager()
    theme_cls.primary_palette = ("Teal")
    title = ("App")

    def build(self):
        c = LayoutPy()
        return c


if __name__ == "__main__":
    KivyGUI().run()

I cut a lot of Python code so it is a bit more clear for you. I don't think that it is a problem with the module itself because the KivyMD example code works fine for me (Thats also what the solution should look like when I run it). I think the problem is that my LayoutPy class inherits from FloatLayout which has no toggle_nav_drawer object... but I have no idea now how I could implement a suitable solution into my existing code (I am trying for 2 days now). If you need the whole code (everything almost worked fine before adding the NavigationDrawer) you can take a look here.

Many thanks in advance!

回答1:

Error - AttributeError

     left_action_items: [['dots-vertical', lambda x: root.toggle_nav_drawer()]]
   File "kivy\weakproxy.pyx", line 32, in kivy.weakproxy.WeakProxy.__getattr__
 AttributeError: 'LayoutPy' object has no attribute 'toggle_nav_drawer'

Root Cause

The object, LayoutPy does not has an attribute toggle_nav_drawer because the toggle_nav_drawer is defined in the instantiated child, NavigationLayout: of LayoutPy.

Solution

Replace root.toggle_nav_drawer() with root.ids.nav_layout.toggle_nav_drawer()

Snippets - kv file

BoxLayout:
    orientation: 'vertical'

    MDToolbar:
        id: toolbar
        title: 'Menu'
        md_bg_color: app.theme_cls.primary_color
        background_palette: 'Primary'
        background_hue: '500'
        left_action_items: [['dots-vertical', lambda x: root.ids.nav_layout.toggle_nav_drawer()]]