Kivy：弹出窗口只能有一个小部件作为内容

我在 .kv 文件中使用弹出窗口时遇到问题。我知道弹出窗口只能有一个小部件作为其内容，但是如果我只将 GridLayout 作为包含标签和按钮的子项传递，这不应该起作用吗？

这是我的Python代码：

import kivy, LabelB
from kivy.app import App
from kivy.graphics import Color, Rectangle
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.gridlayout import GridLayout
from kivy.uix.tabbedpanel import TabbedPanel
from kivy.properties import ObjectProperty, StringProperty
from kivy.lang import Builder
from kivy.uix.popup import Popup
from kivy.uix.screenmanager import ScreenManager, Screen, FadeTransition

Builder.load_file('main.kv')

class CustomPopup(Popup):
    pass

class MenuScreen(Screen):

    def open_popup(self):
        the_popup = CustomPopup()
        the_popup.open()

class SurveyScreen(Screen):
    pass

sm = ScreenManager(transition=FadeTransition())
sm.add_widget(MenuScreen(name='menu'))
sm.add_widget(SurveyScreen(name='survey'))

class MainApp(App):

    def build(self):
        return sm

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

这是我的 .kv 文件：

<CustomPopup>:
    title: 'Terms of Service'
    size_hint: .5, .5
    auto_dismiss: False
    GridLayout:
        cols: 1
        Label:
            size_hint: .9, .9
            halign: 'center'
            valign: 'middle'
            text: 'Insert terms of service text here'
            text_size: self.width, None
        Button:
            text: 'Close'
            on_release: root.dismiss()

<MenuScreen>:

    FloatLayout:

        canvas.before:
            Rectangle:
                source: 'menu.png'
                size: self.size
                pos: self.pos

        Label:
            pos_hint: {'x': .7, 'y': .85}
            text_size: self.size
            font_name: 'Arial'
            font_size: 26
            text: 'Sample'
            bold: True

        Button:
            text: 'Take Survey'
            size_hint: .2, .1
            pos_hint: {'x': .15, 'y': .1}
            on_release:
                root.manager.transition.duration = 0.5
                root.manager.current = 'survey'

        Button:
            text: 'Terms of Service'
            size_hint: .2, .1
            pos_hint: {'x': .6-self.size_hint_x, 'y': .1}
            on_release: root.open_popup()

        Button:
            text: 'Quit'
            size_hint: .2, .1
            pos_hint: {'x': .85-self.size_hint_x, 'y': .1}
            on_release: app.stop()

<SurveyScreen>:

    GridLayout:
        cols: 1
        padding: 20
        spacing: 10

        Label:
            text: 'WELCOME!'
            font_size: 20

        Label:
            text: 'Some boring text'

错误如下：“弹出窗口只能有一个小部件作为内容”

我在这里遗漏了一些明显的东西吗？提前致谢。

是的，它应该像你说的那样工作，你的代码是正确的。

问题是 .kv 文件的加载是重复的。身为你的App子类被称为MainApp, main.kv如果位于同一目录中，则会自动加载（文档：如何加载kv https://kivy.org/docs/guide/lang.html#how-to-load-kv）。另一方面，您使用显式上传文件Builder.load_file ('main.kv').

您必须删除对Builder或重命名MainApp/main.kv.

如果您删除对Builder.load_file你必须创建ScreenManager加载 .kv 后的实例。你可以这样做：

class MainApp (App):

     def build (self):
         sm = ScreenManager (transition = FadeTransition ())
         sm.add_widget (MenuScreen (name = 'menu'))
         sm.add_widget (SurveyScreen (name = 'survey'))
         return sm