Kivy Popup报错‘仅能包含一个内容控件’，代码修复求助

遇到Kivy报错 Popup can have only one widget as content，误以为是重复加载弹窗导致，但无法定位问题。当前代码中ImageWidget仅加载一次，MyPopup仅在button1点击时触发加载。

原代码 #

test.py #

from kivy.app import App
from kivy.uix.widget import Widget
from kivy.properties import StringProperty
from kivy.core.text import LabelBase, DEFAULT_FONT
from kivy.resources import resource_add_path
from random import randint
from kivy.lang import Builder

resource_add_path("./image")

Builder.load_file('cat.kv')


class ImageWidget(Widget):
    source = StringProperty("./image/0.jpg")
    
    def buttonStared(self):
        self.source="./image/0.jpg"

    def buttonRandom(self):
        self.source = f"{randint(0,2)}.jpg"

class MyTestApp(App):
    def build(self):
        return ImageWidget()

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

cat.kv #

#:import Factory kivy.factory.Factory

<MyPopup@Popup>:
    auto_dismiss:False
    orientation: "vertical"
    size_hint: 0.5, 0.5
    title:"Popup "
    Label:
        text: "reset OK？"
        center: root.center
    BoxLayout:
        Button:
            text: "OK"
        Button:
            text: "NO"

<ImageWidget>:
    canvas.before:
        Rectangle:
            pos: self.pos
            size: self.size
    BoxLayout:
        orientation: "vertical"
        size: root.size
        Image:
            source: root.source
        BoxLayout:
            Button:
                id: button1
                text : "Go back to first cat Image"
                on_press: Factory.MyPopup().open()

            Button:
                id: button2
                text: "Rondom Image"
                on_press : root.buttonRandom()

报错的根本原因不是重复加载弹窗，而是Popup组件只能有一个直接子控件作为content。你在<MyPopup@Popup>中直接添加了Label和BoxLayout两个同级控件，违反了这个规则。

修改cat.kv中的MyPopup定义，将所有子控件放入一个容器（比如垂直布局）中，确保Popup只有一个直接子控件：

#:import Factory kivy.factory.Factory

<MyPopup@Popup>:
    auto_dismiss:False
    size_hint: 0.5, 0.5
    title:"Popup "
    # 用垂直布局包裹所有内容，作为Popup的唯一content
    BoxLayout:
        orientation: "vertical"
        padding: 20
        spacing: 20
        Label:
            text: "reset OK？"
            size_hint_y: None
            height: self.texture_size[1]
            center_x: root.center_x
        BoxLayout:
            size_hint_y: None
            height: 40
            Button:
                text: "OK"
                on_press: root.dismiss()  # 添加关闭弹窗逻辑
            Button:
                text: "NO"
                on_press: root.dismiss()  # 添加关闭弹窗逻辑

<ImageWidget>:
    canvas.before:
        Rectangle:
            pos: self.pos
            size: self.size
    BoxLayout:
        orientation: "vertical"
        size: root.size
        Image:
            source: root.source
        BoxLayout:
            Button:
                id: button1
                text : "Go back to first cat Image"
                on_press: Factory.MyPopup().open()

            Button:
                id: button2
                text: "Rondom Image"
                on_press : root.buttonRandom()

额外补充两个实用细节：

• 给OK/NO按钮添加root.dismiss()，点击后可关闭弹窗，避免弹窗无法关闭的问题
• 调整布局的padding、spacing和size_hint，让弹窗内容排版更美观合理

内容的提问来源于stack exchange，提问作者orilyn