在 Kivy 中制作（继续）选项屏幕

Question

我正在努力获得一个在所有屏幕上都相同的选项菜单。选项菜单是一个带有几个选项的弹出窗口。调用弹出窗口时，它不会保存输入。当 Switch 按钮更改为非活动状态时，在用户关闭并重新打开弹出窗口后，它默认恢复为活动状态。

如何保存用户的输入？

from kivy.app import App
from kivy.core.window import Window
from kivy.lang import Builder
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.popup import Popup
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.uix.switch import Switch

Builder.load_string('''

<OptionMenu@Button>:
    text: "Option Menu"
    size_hint_y: .3
    on_press:
        app.option_menu_function()

<BoxLayout@BoxLayout>:
    orientation: "vertical"

<HomeScreen>:
    BoxLayout:
        OptionMenu:
        Label:
            text: "Home Screen"
        Button:
            text: "Next Screen >"
            on_release:
                app.root.current = "screen1"
<Screen1>:
    BoxLayout:
        OptionMenu:
        Label:
            text: "Screen 2"
        Button:
            text: "Next Screen >"
            on_release:
                app.root.current = "homescreen"
<SM>:
    name: "sm"
    id: sm
    HomeScreen:
        name: "homescreen"
        id: hs
    Screen1:
        name: "screen1"
        id: s1
''')

class HomeScreen(Screen):
    pass
class Screen1(Screen):
    pass
class SM(ScreenManager):
    pass

class MyApp(App):

    def build(self):
        global sm
        sm = SM()
        return sm

    def option_menu_function(self):
        box = BoxLayout(orientation = "horizontal")
        switch = Switch(active = True)
        popup = Popup(content = box, auto_dismiss = True, size_hint = (None, None), size = (Window.width/1.5, Window.width/1.5))
        box.add_widget(switch)
        popup.open()

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

Answer 1

之所以不保存widget的状态，是因为你每时每刻都在创建一个新的widget，所以解决办法是重复使用。另一方面，避免使用全局变量，因为它们可能会导致问题，在必须使用它们的情况下。综合以上情况，解决方案如下：

class MyApp(App):
    def build(self):
        box = BoxLayout(orientation = "horizontal")
        box.add_widget(Switch(active = True))
        # a single popup is created
        self.popup = Popup(content = box, auto_dismiss = True, size_hint = (None, None), size = (Window.width/1.5, Window.width/1.5))

        self.root = SM()
        return self.root

    def option_menu_function(self):
        self.popup.open()