在Kivy lang和python中访问子窗口小部件属性的值 [英] Accessing value of child widget property in kivy lang and python

问题描述

1. 如何覆盖Kivy小部件的子项的默认值?即MyWidget.label是'default'但我想将其更改为MyRootWidget的孩子时是紫色乌龟"?

1. How can I overwrite the default value of a Kivy widget's child? i.e. MyWidget.label is 'default' but I want to change it to e.g. 'purple turtle' when a child of MyRootWidget?

我可以像在MyRootWidget.__init__()中那样访问孩子的孩子，但是这似乎很麻烦，尤其是对于一棵深树……是否有更优雅的方法呢?

I can access the children of children as I've done in MyRootWidget.__init__(), but it seems cumbersome, especially for a deep tree ... is there a more elegant way of doing it?

我一直在查看Kivy lang和Widget页面，但如果有解决方案，则无法理解.我在SO页面中还没有看到过这个问题(尽管我在搜索时确实回答了一个不同的问题).

I've been looking over the Kivy lang and Widget pages, but haven't been able to understand a solution if it's there. I haven't seen quite this issue in SO pages (though the did answer a different question while I was searching).

from kivy.app import App
from kivy.lang import Builder
from kivy.uix.boxlayout import BoxLayout
from kivy.properties import ObjectProperty, StringProperty


root = Builder.load_string('''
<MyWidget@BoxLayout>:
    orientation: 'vertical'
    Label:
        id: label
        text: 'DEFAULT'

<MyRootWidget@BoxLayout>:
    id: root_widget
    MyWidget:
        id: w1
        # (---1---) 
''')


class MyRootWidget(BoxLayout):
    w1 = ObjectProperty()

    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        print(self.ids.w1.ids.label.text)  # (---2---)


class MainApp(App):
    def build(self):
        return MyRootWidget()


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

推荐答案

首先，在实现任何代码之前，必须设计您的类.

First of all, before implementing any code, you must design your classes.

首先，我们将使用MyWidget进行处理，在您的要求中，您指示您希望文本是可修改的，因此它必须是根属性.

First we will do it with MyWidget, in your requirements you indicate that you want the text to be modifiable so it must be a root property.

MyWidget
┌--------------------------┐
|                          |
| ┌-------------┐   text---┼--->
| | Label       |     |    |
| |    *text ---┼-----┘    |
| └-------------┘          |
└--------------------------┘

使用MyRootWidget也可以这样做:

The same could be done with MyRootWidget:

MyRootWidget
┌-----------------------------┐
|                             |
| ┌-------------┐ obj_widget--┼--->
| | MyWidget  --┼-----┘       |
| |             |             |
| └-------------┘             |
└-----------------------------┘

属性的深度取决于您的要求，但是如果我们观察到公开一个属性，则意味着在根中创建一个属性并进行绑定，以便在修改根属性时也可以修改内部属性.

The depth of the property depends on your requirements, but if we observe exposing a property it implies creating a property in the root and making a binding so that when the root property is modified the internal property is modified as well.

实施以上操作，您将获得以下内容:

Implementing the above you get the following:

from kivy.app import App
from kivy.lang import Builder
from kivy.uix.boxlayout import BoxLayout
from kivy.properties import ObjectProperty, StringProperty

root = Builder.load_string('''
<MyWidget@BoxLayout>:
    text: "DEFAULT"
    obj_label: label
    orientation: 'vertical'
    Label:
        id: label
        text: root.text

<MyRootWidget@BoxLayout>:
    obj_widget: w1
    MyWidget:
        id: w1
        text: "purple turtle"
''')

class MyRootWidget(BoxLayout):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        print(self.obj_widget.text) 

class MainApp(App):
    def build(self):
        return MyRootWidget()

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

因此，要避免使用id，您可以像创建wid的obj_widget一样为子代小部件创建别名.

So to avoid the ids you can create an alias to the children widget like I did with obj_widget which is an alias of w1.

根据设计，您不应直接访问完整的树，而必须修改图层的属性，如果该图层被修改，则必须在其内部更新必需的数据，以免避免类之间的耦合.

By design you should not access the complete tree directly but you must modify the property of a layer and this layer if it is modified then you must update the necessary data in its internal part so we avoid the coupling between classes.

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