单击按钮不会在kivymd中更改屏幕

Question

我是kivy的新手，却不明白为什么我在导航抽屉中的按钮没有更改为kivymd中的另一个类在类ContentNavigationDrawer上单击时有一个按钮，我希望它更改为另一个屏幕我不明白为什么它没有改变我已经阅读了有关ScreenManager的文档，但仍然无法理解

这是我的代码main.py

from kivy.clock import Clock
from kivy.properties import StringProperty
from kivy.uix.screenmanager import Screen, ScreenManager
from kivymd.app import MDApp
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.floatlayout import FloatLayout


class AboutUs(Screen):
    pass


class Share(FloatLayout):
    data = {
        "facebook": "Facebook",
        "whatsapp": "WhatsApp",
        "instagram": "Instagram",
    }

    def callback(self, instance):
        print('Hello')
        print(instance.icon)



class ContentNavigationDrawer(BoxLayout):
    def hllo(self):
        print('Hello though')


class MainScreen(FloatLayout):

    def quote(self, *args):
        self.quote_text = 'I often think that the night is more alive and more richly colored than  
                                    the day. -Vincent van Gogh '
    quote_text = StringProperty()


class TtApp(MDApp):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        self.title = "Story A Day"
        self.theme_cls.theme_style = "Light"

    def build(self):
        self.theme_cls.primary_palette = "Blue"  # "Purple", "Red"
        main = MainScreen()
        Clock.schedule_once(main.quote, 5)


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

和这是我的main.kv文件

Screen:
    AboutUs:

    MainScreen:

    NavigationLayout:

        ScreenManager:

            Screen:

                BoxLayout:
                    orientation: 'vertical'

                    MDToolbar:
                        title: "Quote"
                        anchor_title: 'left'
                        elevation: 10
                        left_action_items: [['menu', lambda x: nav_drawer.set_state()]]
                        mode: "free-center"

                    Widget:



        MDNavigationDrawer:
            title: 'Quote'
            id: nav_drawer
            swipe_distance: 10

            ContentNavigationDrawer:
                id: content_drawer


<ContentNavigationDrawer>
    name: 'main'
    background_color: 2, 3, 4, 5
    orientation: "vertical"
    padding: "8dp"
    spacing: "8dp"

    AnchorLayout:
        anchor_x: "right"
        size_hint_y: None
        height: avatar.height

        Image:
            id: avatar
            size_hint: None, None
            size: "56dp", "56dp"
            source: "data/logo/kivy-icon-256.png"

        MDLabel:
            anchor_y: 'left'
            text: "[b]Story A Day[/b]"
            theme_text_color: "Custom"
            text_color: 0, 0, 0, 1
            markup: True
            font_style: "H4"
            size_hint_y: None
            height: self.texture_size[1]

    MDRaisedButton:
        md_bg_color: 0, 0, 0, 1
        text: 'You Can'
        on_release: root.hllo()

    MDRaisedButton:
        text: 'Click Me'
        on_release: print('Hell')

    MDLabel:
        text: 'Story A Day' 
        font_style: "Button"
        size_hint_y: None
        height: self.texture_size[1]

    OneLineAvatarListItem:
        text: "About Us"

        IconLeftWidget:
            icon: "information"

    Button:
        text: 'hello'
        on_release: app.root.manager.current = 'Abt'


    ScrollView:


<MainScreen>:
    canvas:
        Color:
            rgba: 0, 0, 0, 1 
        Rectangle:
            pos: self.pos
            size: self.size

    Label:
        id: quote
        text: root.quote_text
        font_size: '20sp'
        size: self.texture_size
        pos_hint: {'x': -0.2, 'y': 0.27}


<AboutUs>:
    name: 'Abt'
    Label:
        text: 'Hellooo'

Answer 1

您必须将ScreenManger作为规则窗口小部件，并将MainScreen首先放置，最后将AboutUs类放置。