如何访问.kv文件中的.kv变量

Question

from kivy.app import App
from kivy.uix.widget import Widget
from kivy.core.window import Window
from kivy.uix.label import Label


Balance = 0
Balance_string = str(Balance)

class MyWidget(Widget):
    def ads(self):
        global Balance
        Balance += 0.25
        Balance_string = str(Balance)
        print(Balance_string)
        return Balance_string

class BuzzMoneyApp(App):
    def build(self):
        return MyWidget()

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

**我的.kv文件**

<MyWidget>:
    canvas:
        Color:
            rgb: (0, 150,0)
        Rectangle:
            pos: self.pos
            size: self.size

    Button:
        center: self.parent.center
        font_size: 14
        height: 28
        background_color: (1.0, 0.0, 0.0, 1.0)
        text: "Earn money"
        on_press:root.ads()

我想从我的main.py中访问.kv文件中的Balance字符串变量，这样我就可以在屏幕上显示它。

Answer 1

您可以轻松地从Properties内部的python中引用kv。下面是您的代码的修改版本，可以这样做：

from kivy.app import App
from kivy.lang import Builder
from kivy.properties import NumericProperty, StringProperty
from kivy.uix.widget import Widget

# Balance = 0
# Balance_string = str(Balance)

class MyWidget(Widget):
    Balance = NumericProperty(0)
    Balance_string = StringProperty('0')

    def ads(self):
        self.Balance += 0.25
        print(self.Balance_string)

    def on_Balance(self, *args):
        # update Balance_string whenever Balance changes
        self.Balance_string = str(self.Balance)

class BuzzMoneyApp(App):
    def build(self):
        return MyWidget()

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

然后可以在Properties中引用kv中的那些

<MyWidget>:
    canvas:
        Color:
            rgb: (0, 150,0)
        Rectangle:
            pos: self.pos
            size: self.size

    Button:
        center: self.parent.center
        font_size: 14
        height: 28
        background_color: (1.0, 0.0, 0.0, 1.0)
        text: "Earn money"
        on_press:root.ads()
    Label:
        text: root.Balance_string  # root.Balance_string can be replaced with just str(root.Balance)
        size_hint: None, None
        size: self.texture_size
        pos: 300, 200
        color: 0,0,0,1

Properties必须在EventDispatcher (通常是Widget)中定义。on_Balance()方法在Balance Property更改时自动触发，并更新Balance_string Property。如图所示，Balance_string可以在kv中使用，每当Balance_string Property发生变化时，Label将被更新。因为Balance_string只是Balance的字符串值，所以可以在kv中消除它并替换为str(root.Balance)。