python - 如何使用python类在kivy中使用下拉小部件

Question

所以，我认为至少应该有两种方法可以让我在这个页面上有一个下拉菜单，但我都无法使用。我是 kivy 和一般编程的新手，但我已经阅读了文档，但似乎我根本不明白。

我创建了以下示例:

import kivy
kivy.require('1.7.2') # replace with your current kivy version !

from kivy.app import App
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.properties import ObjectProperty
from kivy.uix.button import Button
from kivy.uix.dropdown import DropDown

class CustomDropDown(DropDown):
    pass

class HomeScreen(Screen):
    translateInput = ObjectProperty(None)
    translateButton = ObjectProperty(None)
    translateLabel = ObjectProperty(None)
    top_layout = ObjectProperty(None)
    dd_btn = ObjectProperty(None)
    drop_down = CustomDropDown()
    #notes_dropdown = ObjectProperty(None)


    dropdown = DropDown()
    notes = ['Features', 'Suggestions', 'Abreviations', 'Miscellaneous']
    for note in notes:
        # when adding widgets, we need to specify the height manually (disabling
        # the size_hint_y) so the dropdown can calculate the area it needs.
        btn = Button(text='%r' % note, size_hint_y=None, height=30)

        # for each button, attach a callback that will call the select() method
        # on the dropdown. We'll pass the text of the button as the data of the
        # selection.
        btn.bind(on_release=lambda btn: dropdown.select(btn.text))

        # then add the button inside the dropdown
        dropdown.add_widget(btn)

    # create a big main button
    mainbutton = Button(text='Usage Notes 2', size_hint=(1, 1))

    # show the dropdown menu when the main button is released
    # note: all the bind() calls pass the instance of the caller (here, the
    # mainbutton instance) as the first argument of the callback (here,
    # dropdown.open.).
    mainbutton.bind(on_release=dropdown.open)
    #dd_btn.bind(on_release=dropdown.open)

    # one last thing, listen for the selection in the dropdown list and
    # assign the data to the button text.
    dropdown.bind(on_select=lambda instance, x: setattr(mainbutton, 'text', x))
    #dropdown.bind(on_select=lambda instance, x: setattr(dd_btn, 'text', x))

    #top_layout.add_widget(mainbutton)


class dropdApp(App):

    def build(self):

        return HomeScreen()



if __name__ == '__main__':
    dropdApp().run()

这是对应的 .kv 文件:

#:kivy 1.7.2

<CustomDropDown>:
    Button:
        text: 'My first Item'
        size_hint_y: None
        height: 44
        on_release: root.select('item1')
    Label:
        text: 'Unselectable item'
        size_hint_y: None
        height: 44
    Button:
        text: 'My second Item'
        size_hint_y: None
        height: 44
        on_release: root.select('item2')

<HomeScreen>:
    id: home_screen
    translateInput: translateInputID
    translateButton: translateButtonID
    translateLabel: labelID
    top_layout: topLayoutID
    #notes_dropdown: notesDropDownID
    dd_btn: btn_ddID

    orientation: 'vertical'
    FloatLayout:
        size_hint: 1, .95
        TextInput:
            id: translateInputID
            text: 'cove'
            #text: 'ﻰﺸَﻣ'
            font_name: "data/fonts/DejaVuSans.ttf"
            background_color: 1, 1, 1, 1
            size_hint: .75, .1
            multiline: False
            pos_hint: {'x': .125, 'y': .45}
            text_size: self.size
            valign: 'middle'
            halign: 'center'
            padding: 5

        Button:
            id: translateButtonID
            text: 'Translate'
            pos_hint: {'x': .35, 'y': .35}
            size_hint: .3, .08
            valign: 'middle'
            halign: 'center'
            text_size: self.size
            on_release: root.translateButtonPressed()
            #on_press: root.manager.current = 'resultsscreen'

        Label:
            id: labelID
            text: 'Translator'
            text_size: self.size
            valign: 'middle'
            halign: 'center'
            pos_hint: {'x': .3, 'y': .75}
            size_hint: .4, .2
            #font_name: "simpo.ttf"
            #font_name: "5thgradecursive.ttf"
            #font_name: "AGA-Rasheeq-Regular.ttf"
            font_name: "data/fonts/DejaVuSans.ttf"
            font_size: 50

    BoxLayout:
        id: topLayoutID
        #cols: 2
        size_hint: 1, .05
        pos_hint: {'x': 0, 'y': .95}
        Button:
            #id: notesDropDownID 
            id: btn_ddID
            text: 'Usage Notes'
            on_release: root.drop_down.open
        Button:
            text: 'About'

1. 第一个下拉菜单应附加到 kv 文件底部已创建的按钮“使用说明”。它附加到 python 中的类“CustomDropDown”，以及 kv 文件中的相应类。你可能会注意到这个例子直接来自 kivy 文档。我想通过创建这条线:

   drop_down = CustomDropDown()
   

   它为我提供了 python 和 kivy 方面的句柄来操作它，但正如您可能注意到的那样，当您运行它并单击“使用说明”时，没有任何反应。

2. 第二个下拉菜单也是按照 kivy 文档用 python 创建的。我认为它会在应用程序顶部创建第三个按钮，标题为“使用说明 2”。我只是在尝试添加它时遇到错误。现在该行(在我的文件中为 53):

   top_layout.add_widget(mainbutton)
   

   被注释掉或应用程序甚至无法运行，引发错误:

   AttributeError: 'kivy.properties.ObjectProperty' object has no attribute 'add_widget'
   

   我意识到我确实设置了

   top_layout = ObjectProperty(None)
   

   但这就是 kivy 建议对许多小部件执行的操作，我已经对许多其他小部件执行了操作而没有出现此错误。

我确信其中一个或两个问题对外面的人来说很简单。我错过了什么？

Answer 1

我在这里发布这个，希望它能帮助其他只想要一个可以放在 .kv 文件中的下拉按钮的 kivy 初学者。

class DropBut(Button):
    def __init__(self, **kwargs):
        super(DropBut, self).__init__(**kwargs)
        self.drop_list = None
        self.drop_list = DropDown()

        types = ['Item1', 'Item2', 'Item3', 'Item4', 'Item5', 'Item6']

        for i in types:
            btn = Button(text=i, size_hint_y=None, height=50)
            btn.bind(on_release=lambda btn: self.drop_list.select(btn.text))
           
            self.drop_list.add_widget(btn)

        self.bind(on_release=self.drop_list.open)
        self.drop_list.bind(on_select=lambda instance, x: setattr(self, 'text', x))