Question

我有一个按钮（button_child_A），用on_press调用def。在这个def中，我想更改3个标签的文本：

- `label_child_A` is in the same class as the `button_child_A`
- `label_parent`  is in the parent class of `button_child_A`
- `label_child_B` is in the sister class of `button_child_A` (same parent class)

我可以通过简单地调用label_child_A来修改label_parent和ids，但我无法通过调用label_child_B修改id，我得到错误："object has no attribute"。（参见下面def change_label中的.py）

我知道我必须创建ObjectProperty，但为什么？当我从同一个类或父类更改窗口小部件时，为什么我不需要ObjectProperty但是当我从“姐妹类”（同一个父级）更改窗口小部件时我需要它？

.py：

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


class Class_Parent(BoxLayout):
    pass

class Class_Child_A(BoxLayout):
    def change_labels(self):
        self.ids.label_child_A.text = "changed"
        self.parent.ids.label_parent.text= "changed"
        #self.parent.ids.classAb_id.label_child_B.text = "changed"  ## get the error 'Class_Child_B' object has no attribute 'label_child_B'
        self.parent.ids.classAb_id.label_child_b_object_property.text = "changed"   # why do I need to use ObjectProperty here ?  
    pass


class Class_Child_B(BoxLayout):
    child_b_label_object_property = ObjectProperty(None)


class TestApp(App):
    def build(self):
        return Class_Parent()
TestApp().run()

.kv：

<Class_Parent>:
    Label:
        id: label_parent
        text: "label parent"
    Class_Child_A:
        id: classAa_id
    Class_Child_B:
        id: classAb_id


<Class_Child_A>:
    Button:
        id: button_child_A
        text: "button child A"
        on_press: root.change_labels()

    Label:
        id: label_child_A
        text: "label child A"

<Class_Child_B>:
    label_child_b_object_property: label_child_B
    Label:
        id: label_child_B
        text: "label child B"

Kivy：何时使用ObjectProperty

0 个答案: