猕猴桃外部规则继承2 [英] Kivy outside rule inherence 2

问题描述

作为后续问题:

• Kivy外部规则继承
• 通过add_widget()进行基辅规则继承

• Kivy outside rule inherence
• Kivy rule inherence with add_widget()

main.py

import os
from kivy.app import App
from kivy.uix.button import Button
from kivy.uix.stacklayout import StackLayout
from kivy.properties import ObjectProperty


class FancyButton(Button):
    imp = ObjectProperty(None)


class Important(StackLayout):

    font_kanji = os.path.join('fonts', 'TakaoPMincho.ttf')

    def NoInspiration(self, smile):
        print("Received: {}".format(smile))

    def AddFancy(self):
        print(self.ids)
        temp = FancyButton(text='f', imp = self)
        self.ids.boxy.add_widget(temp)


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

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

test.kv

#:kivy 1.9.0

<FancyButton>:
    font_name: self.imp.font_kanji  # ERROR
    on_release: self.imp.NoInspiration(':)')  # WORKS


<Important>:
    id: imp

    BoxLayout:
        id: boxy
        orientation: 'vertical'

        FancyButton:
            text: "smiley"
            imp: root

        Button:
            text: "add fancy"
            on_release: imp.AddFancy()


BoxLayout:
    Important

在上面的示例中，'on_release:self.imp.NoInspiration(':)')'有效是因为FancyButton具有'imp:root'.

In the above example 'on_release: self.imp.NoInspiration(':)')' works because FancyButton has 'imp: root'.

但是'font_name:self.imp.font_kanji'不起作用，并显示错误消息:

However 'font_name: self.imp.font_kanji' doesn't work and gives the error:

AttributeError:"NoneType"对象没有属性"font_kanji"

AttributeError: 'NoneType' object has no attribute 'font_kanji'

我的猜测是这样做的原因是on_release发生在所有小部件都直接加载并且输入font_name之后，因此没有'imp:root'.

My guess is the reason for this is that on_release takes place after all widgets are loaded and font_name directly, so without having 'imp: root'.

我也尝试过:

font_kanji = StringProperty(os.path.join('fonts', 'TakaoPMincho.ttf'))

，但无济于事.

如何获得font_name引用font_kanji?我应该使用全局吗?如果是，您将如何在Python中设置一个可以在.kv中访问的全局变量?

How do I get font_name refer to font_kanji? Should I use global? If yes, how would you set a global in Python which can be accessed in the .kv?

(如果将global放在font_Kanji的前面，并在.kv文件中删除"self.imp"，则会出现错误:"NameError:未定义name'font_kanji'")

(If I put global in front of font_Kanji and remove 'self.imp' in the .kv file I get the error: " NameError: name 'font_kanji' is not defined")

推荐答案

您的猜测是正确的:创建按钮时，其imp属性为None.解决此问题的一种方法是观察imp属性并在其处理程序中设置font_name的值:

Your guess is right: when your button is created its imp property is None. One to go around this would be to observe imp property and set the value of font_name in its handler:

class FancyButton(Button):
    imp = ObjectProperty(None)

    def on_imp(self, obj, imp):
        if imp:
            self.font_name = imp.font_kanji

通过这种方式，可以在使用适当的Important实例初始化imp属性后设置字体.此方法的缺点是Instance.font_kanji的更改不会触发FancyButton.font_name的更改.

This way the font is set after imp property is initialzied with proper Important instance. The dissadvantage of this method is that changes of Instance.font_kanji won't trigger changes of FancyButton.font_name.

如果要绑定两个属性，则必须为动态创建的FancyButton实例从Instance.font_kanji端调用bind函数(因为我们要对它的更改做出反应):

If you want to have both properties binded, then you have to call bind funtion from Instance.font_kanji side (since we want to react to its changes) for dynamically created FancyButton instances:

class Important(StackLayout):
    font_kanji = os.path.join('fonts', 'TakaoPMincho.ttf')

    def NoInspiration(self, smile):
        print("Received: {}".format(smile))

    def AddFancy(self):
        temp = FancyButton(text='f', imp = self)
        self.bind(font_kanji=temp.setter('font_name'))
        self.ids.boxy.add_widget(temp)

用kv语言定义的接口可以直接进行绑定:

Interface defined in the kv language can do the binding directly:

<Important>:
    id: imp

    BoxLayout:
        id: boxy
        orientation: 'vertical'

        FancyButton:
            text: "smiley"
            font_name: root.font_kanji
            imp: root

        Button:
            text: "add fancy"
            on_release: imp.AddFancy()
''')

这篇关于猕猴桃外部规则继承2的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！