Kivy tutorial 004: Making the GUI do stuff, binding to events

Kivy tutorial 004: Making the GUI do stuff, binding to events – Kivy Blog

Central themes: Events and Kivy properties
中心主题：事件和kivy属性

We left the last tutorial with a calculator app GUI with some nice automatic behaviour, but which doesn’t actually do anything. Let’s change that; it’s time to learn about binding events.
上次导师课我们留下了一个有着一些不错的自动行为的计算机GUI，但是这真是啥也不干。让我们改变它，是时候了解绑定事件了。

To refresh, the basic calculator GUI code was as follows. If you modified it to experiment, feel free to continue with your modified code, and try to change the instructions to fit your modifications:
为了重新刷新，基本的计算机GUI代码像下面一样。如果你修改它来体验，随意继续修改你的代码，并且试着改变结构来达到你的修改。

from kivy.app import App
from kivy.uix.button import Button
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.gridlayout import GridLayout
from kivy.uix.label import Label


class YourApp(App):
    def build(self):
        root_widget = BoxLayout(orientation='vertical')

        output_label = Label(size_hint_y=1)

        button_symbols = ('1', '2', '3', '+',
                          '4', '5', '6', '-',
                          '7', '8', '9', '.',
                          '0', '*', '/', '=')

        button_grid = GridLayout(cols=4, size_hint_y=2)
        for symbol in button_symbols:
            button_grid.add_widget(Button(text=symbol))

        clear_button = Button(text='clear', size_hint_y=None,
                              height=100)

        root_widget.add_widget(output_label)
        root_widget.add_widget(button_grid)
        root_widget.add_widget(clear_button)

        return root_widget


YourApp().run()

Note

This tutorial introduces some major new Kivy concepts. I recommend working through it even if you don’t entirely follow what’s going on, then going back to modify components and see how things change.
这节导师课介绍一些主要的kivy概念。 我建议克服它尽管你没有整个的跟随事态的进行，然后返回修改部件并且看看事如何改变的。

The plan now is that every one of these buttons should add their symbol to the Label at the top, except ‘=’ which should evaluate the code and display the result. This is obviously an extremely basic calculator, but the point here is to showcase some Kivy basics - if you’d like to improve the interface, go ahead with trying to do so along the way.
现在的计划是每个按钮应该增加他们的符号到标签的上面， 除了=号应该求值并且展示结果。这是一个极其明显的基础的计算机，但是这的关键点是展示一些kivy的基本要素-如果你想来提升界面，继续沿着这种方式继续尝试。

To make the buttons do something, we must&nb