Kivy:自我更新标签文字 [英] Kivy: Self-updating label text

问题描述

比方说，我有3个类:发生内容的唤醒类"，标签类和包含它们的类. 例如，标签类可以是一个状态栏，显示正在上班的某物的状态.我希望我能找到一种方法来使标签自动更新要显示的值，因为该值是在后者内部更改的工作类的值.

Let's say I have 3 classes: a "woking class" where stuff takes place, a label class and a class to contain them. For example the label class could be a status bar showing the status of something going on the working class. I wish I could find a way to make the label self-update the value to show, since this value is a value of the working class being changed inside the latter.

这里有一个示例代码

Builder.load_string('''
<CustomLabel>
    text: 'Value is {}'.format(root.value)

<WorkingClass>:
    orientation: 'vertical'

    Button:
        text: 'Update'
        on_release: root.update()

<MainLayout>
    orientation: 'vertical'

''')

class CustomLabel(Label):
    value = NumericProperty()

class WorkingClass(BoxLayout):

    def __init__(self, *args, **kwargs):

        super(WorkingClass, self).__init__(*args, **kwargs)

        self.a = 5

    def update(self):
        self.a += 1
        print(self.a)

class MainLayout(BoxLayout):

    def __init__(self, *args, **kwargs):

        super(MainLayout, self).__init__(*args, **kwargs)

        self.workingClass = WorkingClass()
        self.customLabel = CustomLabel(value=self.workingClass.a)

        self.add_widget(self.customLabel)
        self.add_widget(self.workingClass)





class MyApp(App):
    def build(self):
        return MainLayout()

if __name__ == "__main__":
    MyApp().run()

是否可以通过属性或其他方式做到这一点?因为我不想每次更改值时都需要手动更新标签.无论如何要实现这一目标?

Is there a way of doing it with properties or whatever? Becouse I don't want to need to manually update (sommehow) the label each time I change the value. Anyway to achieve this?

推荐答案

您正在更新WorkingClass上的属性，但这不会更新CustomLabel上的值，因为您执行的是直接分配而不是对其进行处理.但是，可以的，您可以使用Property s使一切自动运行.

You're updating a property on WorkingClass, but that doesn't update the value on CustomLabel since you did a direct assignment instead of binding it. But yes, you can use Propertys to make everything work automatically.

在WorkingClass中:

class WorkingClass(BoxLayout):
    a = NumericProperty()

    def __init__(self, **kwargs): ...

这使a成为您可以绑定到的Property.

This makes a into a Property which you can bind to.

然后在MainLayout的构造函数中:

self.workingClass = WorkingClass()
self.customLabel = CustomLabel(value=self.workingClass.a)
self.workingClass.bind(a=self.customLabel.setter('value'))

最后一行说:当self.workingClass上的属性a的值更改时，将self.customLabel的value属性设置为相同的值"

The last line says: "when the value of property a on self.workingClass changes, set the value property of self.customLabel to the same value"

或者，您可以将Property添加到上面的WorkingClass中，然后摆脱MainLayout的构造函数，而使用kv代替:

Alternatively, you could just add the Property to WorkingClass above, then get rid of MainLayout's constructor and use kv instead:

<MainLayout>:
    orientation: 'vertical'

    WorkingClass:
        id: working_class

    CustomLabel:
        value: working_class.a  # assigning one property to another in kv automatically binds

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