关于 kivy.uix.widget.WidgetException 的问题

Question

我是 python 和 kivymd 的新手，我正在尝试开发一个数据输入程序。但是，当我为 selection 创建下拉菜单时，发生了错误，我无法在 select 一个项目后更新文本字段的值。这是 python 代码：

from kivymd.app import MDApp
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.properties import ObjectProperty
from kivy.lang import Builder
from kivy.clock import Clock
from kivy.properties import ObjectProperty
from kivymd.uix.menu import MDDropdownMenu
class AMRMenu(Screen):
    def GIbutton(self):
        sm.current = 'GI'
class GIWindow(Screen):
    weather = ObjectProperty(None)
    menu_weather_items = [{"text":"Sunny"},{"text":"Cloudy"},{"text":"Raining"}]
    menu_FeedResponse_items=[{"text":"High"},{"text":"Medium"},{"text":"Low"}]
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        self.menu = MDDropdownMenu(
                    items=self.menu_weather_items, 
                    width_mult=4,
                    caller = self.weather,
                    callback=self.set_item)
    def set_item(self, instance):
        def set_item(interval):
            self.weather.text = instance.text
            self.menu.dismiss()
        Clock.schedule_once(set_item, 0.5) 
class WindowManager(ScreenManager):
    pass
sm = WindowManager()    

class MainApp(MDApp):   
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        kv = Builder.load_file("FR.kv")
    def build(self):        
        screens = [AMRMenu(name = "menu"), GIWindow(name = "GI")]
        for screen in screens:
            sm.add_widget(screen)
        sm.current = "menu"
        return sm
if __name__ == "__main__":
    MainApp().run()

这是kv。文件：

<AMRMenu>:
    name:"menu"
    BoxLayout:
        orientation: "vertical"
        MDToolbar:
            title: "Main Menu"
        MDList:
            OneLineListItem:
                text: "General Information"
                on_press: root.GIbutton()
            OneLineListItem:
                text: "Water Temperature"
            OneLineListItem
                text: "Feeding Amount"
            OneLineListItem: 
                text: "Residue and Feeding response"
            OneLineListItem: 
                text: "Dead fish"
            OneLineListItem:
                text: "Sell/Use"

<GIWindow>
    name: "GI"

    weather: weather
    ScrollView:
        id: screen
        MDBoxLayout:
            orientation: 'vertical'
            adaptive_height: True

            MDTextField:
                id: weather
                pos_hint: {'center_x': .5, 'center_y': .5}
                hint_text: "Weather"
                icon_right: "arrow-down-drop-circle-outline"
                input_filter: lambda text, from_undo: text[:5 - len(self.text)]
                on_focus: root.menu.open()

错误信息如下：

File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/kivy/core/window/__init__.py", line 1297, in add_widget
 (widget, widget.parent)
 kivy.uix.widget.WidgetException: Cannot add <kivymd.uix.menu.MDDropdownMenu object at 0x7fd2fa31a6e0> to window, it already has a parent <kivy.core.window.window_sdl2.WindowSDL object at 0x7fd2f65826e0>

我不知道我为什么会这样。如果有人弄明白了，它会很有帮助。感谢您阅读此问题

Answer 1

问题是您的 kv 行：

on_focus: root.menu.open()

每次 focus 更改时，

都会打开菜单。因此，即使 focus 变为假，它也会尝试打开菜单。一个简单的解决方法是在 focus is True`:

时打开菜单

on_focus: if self.focus: root.menu.open()

关于 kivy.uix.widget.WidgetException 的问题

Problem about kivy.uix.widget.WidgetException

python

kivy

kivymd