使用DropDown open（）方法打开自定义DropDown不起作用

Question

我在kv文件中定义了一个基本的自定义DropDown。应用程序GUI非常简单，按钮栏位于顶部，TextInput消耗屏幕的其余部分。这是代码：

dropdowntrialgui.py

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.dropdown import DropDown

class CustomDropDown(DropDown):
    pass

class DropDownTrialGUI(BoxLayout):
    dropD = CustomDropDown()

    def openMenu(self, widget):
        self.dropD.open(widget)


class DropDownTrialGUIApp(App):
    def build(self):
        return DropDownTrialGUI()


if __name__== '__main__':
    dbApp = DropDownTrialGUIApp()

    dbApp.run()

和kv文件：

dropdowntrialgui.kv

DropDownTrialGUI:

    <CustomDropDown>
        Button:
            text: 'My first Item'
            size_hint_y: None
            height: '28dp'
            on_release: root.select('item1')
        Button:
            text: 'My second Item'
            size_hint_y: None
            height: '28dp'
            on_release: root.select('item2')

    <DropDownTrialGUI>:
        orientation: "vertical"
        padding: 10
        spacing: 10

        BoxLayout:
            size_hint_y: None
            height: "28dp"
            Button:
                id: toggleHistoryBtn
                text: "History"
                size_hint_x: 15
            Button:
                id: deleteBtn
                text: "Delete"
                size_hint_x: 15
            Button:
                id: replaceBtn
                text: "Replace"
                size_hint_x: 15
            Button:
                id: replayAllBtn
                text: "Replay All"
                size_hint_x: 15
            Button:
                id: menuBtn
                text: "..."
                size_hint_x: 15
                on_press: root.openMenu(self)

        TextInput:
            id: readOnlyLog
            size_hint_y: 1
            readonly: True

按menuBtn无效。我该如何解决这个问题？

Answer 1

您没有正确初始化类，作为一般规则，您不应将任何内容定义为类属性（kivy属性除外），而是通过在窗口中实例化它们来将窗口小部件定义为实例属性。 __init__方法：

class DropDownTrialGUI(BoxLayout):
    def __init__(self, **kwargs):
        super(DropDownTrialGUI, self).__init__(**kwargs)
        self.dropD = CustomDropDown()

    def openMenu(self, widget):
        self.dropD.open(widget)