python - kivy 访问 child ID

Question

我想访问 child 的 id 来决定是否删除小部件。我有以下代码:

主要.py

#!/usr/bin/kivy
# -*- coding: utf-8 -*-

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


class Terminator(BoxLayout):
    def DelButton(self):
        print("Deleting...")

        for child in self.children:
            print(child)
            print(child.text)

            if not child.id == 'deleto':
                print(child.id)
                #self.remove_widget(child)
            else:
                print('No delete')


class TestApp(App):
    def build(self):
        pass


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

测试.kv

#:kivy 1.9.0

<Terminator>:
    id: masta
    orientation: 'vertical'

    Button:
        id: deleto
        text: "Delete"
        on_release: masta.DelButton()

    Button
    Button

Terminator

然而，当使用 print(child.id) 打印 id 时，它总是返回:None。即使 print(child.text) 正确返回 Delete 或 。

问题

• 为什么 child.id 不返回 deleto，而是返回 None？
• 如何检查我没有删除带有“删除”的按钮，而是删除所有其他按钮？

Answer 1

正如您在 documentation 中所读到的那样:

In a widget tree there is often a need to access/reference other widgets. The Kv Language provides a way to do this using id’s. Think of them as class level variables that can only be used in the Kv language.

描述了从 Python 代码访问 ID here .工作示例:

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.lang import Builder
from kivy.properties import ObjectProperty
from kivy.uix.button import Button

Builder.load_string("""
<Terminator>:
    id: masta
    orientation: 'vertical'

    MyButton:
        id: deleto

        button_id: deleto

        text: "Delete"
        on_release: masta.DelButton()

    MyButton
    MyButton
""")

class MyButton(Button):
    button_id = ObjectProperty(None)

class Terminator(BoxLayout):
    def DelButton(self):
        for child in self.children:
            print(child.button_id)       

class TestApp(App):
    def build(self):
        return Terminator()    

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

要跳过删除带有“删除”标签的按钮，您可以检查其 text 属性。但是从循环内部删除会导致错误，因为在您迭代的列表将被更改后，一些子项将被跳过:

class Terminator(BoxLayout):
    def DelButton(self):
        for child in self.children:            
            self.remove_widget(child) # this will leave one child

您必须创建一个要删除的子项列表:

class Terminator(BoxLayout):
    def DelButton(self):
        for child in [child for child in self.children]:            
            self.remove_widget(child) # this will delete all children

在你的情况下:

class Terminator(BoxLayout):
    def DelButton(self):
        for child in [child for child in self.children if child.text != "Delete"]:            
            self.remove_widget(child)