【问题标题】：Display property in Python Kivy在 Python Kivy 中显示属性
【发布时间】：2017-08-22 11:17:06
【问题描述】：

我一直在看一个关于创建计算器的 Kivy 和 Python 教程，但我看到了这个属性：显示小部件 id 的值。使用此值，它可以访问小部件的其他属性。这是代码（.kv 文件）：

<CalcGridLayout>:
    id: calculator
    display: entry #this is the display property
    rows: 5
    padding: 10
    spacing: 10

    BoxLayout:
        TextInput:
            id: entry #with the value of this
            font_size: 32
            multiline: False

    BoxLayout:
        spacing: 10
        Button:
            text: "7"
            on_press: entry.text += self.text
        Button:
            text: "8"
            on_press: entry.text += self.text
        Button:
            text: "9"
            on_press: entry.text += self.text
        Button:
            text: "+"
            on_press: entry.text += self.text

    BoxLayout:
        spacing: 10
        Button:
            text: "4"
            on_press: entry.text += self.text
        Button:
            text: "5"
            on_press: entry.text += self.text
        Button:
            text: "6"
            on_press: entry.text += self.text
        Button:
            text: "-"
            on_press: entry.text += self.text

    BoxLayout:
        spacing: 10
        Button:
            text: "1"
            on_press: entry.text += self.text
        Button:
            text: "2"
            on_press: entry.text += self.text
        Button:
            text: "3"
            on_press: entry.text += self.text
        Button:
            text: "*"
            on_press: entry.text += self.text

    BoxLayout:
        spacing: 10
        Button:
            text: "AC"
            on_press: entry.text = ""
        Button:
            text: "0"
            on_press: entry.text += self.text
        Button:
            text: "="
            on_press: calculator.calculate(entry.text)
        Button:
            text: "/"
            on_press: entry.text += self.text

那个变量/属性是什么？它是干什么用的？

【问题讨论】：

标签： android python python-3.x kivy kivy-language

【解决方案1】：

参考你的kv文件：

calc.kv

display: entry

main.py

display = ObjectProperty(None)

display - 是你的变量，它被声明为 Kivy ObjectProperty。它用于引用在 kv 文件中实例化的 TextInput 子部件。声明 ObjectProperty 后，将其连接到在 kv 文件中创建的子小部件，例如display: entry。完成后，您可以轻松地在 calculate 方法中引用 TextInput 属性。

示例

main.py

from kivy.app import App
from kivy.uix.gridlayout import GridLayout
from kivy.properties import ObjectProperty


class CalcGridLayout(GridLayout):
    display = ObjectProperty(None)

    def calculate(self, dt):
        print(self.display.text)


class CalcApp(App):

    def build(self):
        return CalcGridLayout()


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

calc.kv

#:kivy 1.10.0

<CalcGridLayout>:
    id: calculator
    display: entry #this is the display property
    rows: 5
    padding: 10
    spacing: 10

    BoxLayout:
        TextInput:
            id: entry #with the value of this
            font_size: 32
            multiline: False

    BoxLayout:
        spacing: 10
        Button:
            text: "7"
            on_press: entry.text += self.text
        Button:
            text: "8"
            on_press: entry.text += self.text
        Button:
            text: "9"
            on_press: entry.text += self.text
        Button:
            text: "+"
            on_press: entry.text += self.text

    BoxLayout:
        spacing: 10
        Button:
            text: "4"
            on_press: entry.text += self.text
        Button:
            text: "5"
            on_press: entry.text += self.text
        Button:
            text: "6"
            on_press: entry.text += self.text
        Button:
            text: "-"
            on_press: entry.text += self.text

    BoxLayout:
        spacing: 10
        Button:
            text: "1"
            on_press: entry.text += self.text
        Button:
            text: "2"
            on_press: entry.text += self.text
        Button:
            text: "3"
            on_press: entry.text += self.text
        Button:
            text: "*"
            on_press: entry.text += self.text

    BoxLayout:
        spacing: 10
        Button:
            text: "AC"
            on_press: entry.text = ""
        Button:
            text: "0"
            on_press: entry.text += self.text
        Button:
            text: "="
            on_press: calculator.calculate(entry.text)
        Button:
            text: "/"
            on_press: entry.text += self.text

【讨论】：