如何在 Kivy 中为下一个窗口创建下拉列表

Question

单击第一个屏幕中的按钮后，如何在下一个窗口中创建下拉列表，我尝试启动 kv 文件中的按钮，只是为了在 ModelWindow 屏幕中拥有一个按钮，但下一个问题是 ModelWindow 类中的按钮变量消失了。 lista 方法需要按钮变量才能激活下拉列表

Python 文件

import kivy
from kivy.app import App 
from kivy.uix.label import Label 
from kivy.uix.button import Button 
from kivy.properties import ObjectProperty 
from kivy.lang import Builder
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.uix.dropdown import DropDown
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.label import Label


class ModelWindow(Screen):
    def window(self):
        box = BoxLayout(orientation='vertical')
        label = Label(text='LABEL')
        button = Button(text='Selecione', font_size=30, size_hint_y=0.15, on_release=self.lista)
        box.add_widget(label)
        box.add_widget(button)

        self.dropdown = DropDown()  # Create the dropdown once and keep a reference to it
        self.dropdown.bind(on_select=lambda instance, x: setattr(button, 'text', x))

        for index in range(10):  # create the buttons once
            btn = Button(text='Value %d' % index, size_hint_y=None, height=44,
                            on_release=lambda btn: print(btn.text))  # bind every btn to a print statement
            btn.text = 'Value %d' % index
            btn.bind(on_release=lambda btn: self.dropdown.select(btn.text))
            self.dropdown.add_widget(btn)
        return box

    def lista(self, button):
        # dropdown = DropDown()  <---- DON'T NEED THIS
        # button.bind(on_release=self.dropdown.open)  <---- DON'T NEED THIS
        self.dropdown.open(button)  # you need this to open the dropdown
        # print(button.text)
  

class MainWindow(Screen):
    pass

class SecondWindow(Screen):
    pass

class WindowManager(ScreenManager):
    pass


kv = Builder.load_file("proj.kv")

class MyMainApp(App):
    def build(self):
        return kv

    

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

Kv 文件

 WindowManager:
    MainWindow:
    SecondWindow:
    ModelWindow:

<ModelWindow>:
    name: "model"
 
<MainWindow>:
    name: "main"
    

    BoxLayout:
        orientation: "vertical"
        size: root.width, root.height

        Button:
            text: "Select Model"
            on_press:
                app.root.current = "model" 
                      
        Button:
            text: "Test Model"

        Button:
            text: "Create New Model"
            on_release: 
                app.root.current = "second" 
                root.manager.transition.direction = "left"


<SecondWindow>:
    name: "second"
    Button:
        text: "Go Back"
        on_release:
            app.root.current = "main"
            root.manager.transition.direction = "right"
          

我问是否有人知道如何在下一个窗口中制作下拉列表？我应该把它写在 kv 文件中还是 python 本身？谢谢你

Answer 1

如果我正确理解您的观点，您想要初始化 ModelWindow 类。为此，您可以简单地调用 __init__ 中的方法 window 并进行一些修改，或者直接在 __init__ 中将所有内容定义为，

    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        box = BoxLayout(orientation='vertical')
        label = Label(text='LABEL')
        ...
        # Same as in your method `window`.
            ...
            self.dropdown.add_widget(btn)
        self.add_widget(box)