我想将 kivy list-item 与 on_press:root 绑定。manager.current = 'screen1'

Question

我是初学者（抱歉代码笨拙）。我想编写代码，以便每当我单击 header 中的菜单图标时，导航栏都会切换。项目列表出现在导航栏中。（这有效）当我单击导航栏中的项目时，它会将我带到另一个屏幕（这不起作用）。下面是代码。它显示 'NoneType' 没有 'current'

的属性

from kivy.lang import Builder
from kivy.uix.boxlayout import BoxLayout
from kivymd.theming import ThemableBehavior
from kivymd.uix.list import MDList
from kivy.uix.screenmanager import Screen, ScreenManager

navigation_helper = """
MDScreen:
    MDNavigationLayout:
        ScreenManager:
            MDScreen:
                MDBoxLayout:
                    orientation: 'vertical'
                    MDToolbar:
                        title: 'Title'
                        left_action_items: [["menu", lambda x: nav_drawer.set_state("open")]]
                        elevation:10
                    Widget:
            Screen1:

        MDNavigationDrawer:
            id: nav_drawer
            ContentNavigationDrawer:
                id: content_drawer
                orientation: 'vertical'
                padding: "8dp"
                spacing: "8dp"
                
                AnchorLayout:
                    anchor_x: "left"
                    size_hint_y: None
                    height: avatar.height
                    
                    Image:
                        id: avatar
                        size_hint: None, None
                        size: "180dp", "100dp"
                        source: "logo.png"

                ScrollView:
                    DrawerList:
                        id: md_list

                        MDList:
                            OneLineIconListItem:
                                text: "Screen 1"
                                on_press: root.manager.current = 'screen1'
                                IconLeftWidget:
                                    icon: "account-multiple"
                                    
<Screen1>:
    name: 'screen1'
    MDLabel:
        text: 'Profile'
        halign: 'center'
"""

class Screen1(Screen):
    pass


sm = ScreenManager()
sm.add_widget(Screen1(name='screen1'))


class ContentNavigationDrawer(BoxLayout):
    pass


class DrawerList(ThemableBehavior, MDList):
    pass


class NavBar(MDApp):
    def build(self):
        screen = Builder.load_string(navigation_helper)
        self.theme_cls.primary_palette = 'Indigo'
        return screen

    def on_start(self):
        pass


NavBar().run()

Answer 1

默认情况下 root 是 None，因此当您编写 on_press: root.manager.current = 'screen1' 时会引发预期的错误，AttributeError。

但还要注意，即使您删除了它，您也会收到另一个错误 NameError，因为您没有提供对 'manager'.

的任何引用

因此您需要进行更改，

    MDNavigationLayout:
        ScreenManager:
            id: manager # Use it as id keeping the name as it is.
            MDScreen:

还有，

                        MDList:
                            OneLineIconListItem:
                                text: "Screen 1"
                                on_press: manager.current = 'screen1'
                                IconLeftWidget:
                                    icon: "account-multiple"

我想将 kivy list-item 与 on_press:root 绑定。manager.current = 'screen1'

I want to bind kivy list-item with on_press:root.manager.current = 'screen1'

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