Python|使用 .kv 文件在 Kivy 中切换小部件

Kivy 是Python中一个独立于平台的 GUI 工具。因为它可以在Android、IOS、linux和Windows等平台上运行。它基本上是用来开发Android应用程序的，但这并不意味着它不能在桌面应用程序上使用。

???????? Kivy Tutorial – Learn Kivy with Examples.

切换小部件：

Switch 小部件作为机械灯开关处于活动或非活动状态。用户可以向左/向右滑动以激活/停用它。
开关表示的值是 True 或 False。也就是说，开关可以处于打开位置或关闭位置。
要使用 Switch，您必须导入：

from kivy.uix.switch import Switch

将回调附加到交换机：

• 可以通过回调附加开关以检索开关的值。
• 开关的状态转换是从 ON 到 OFF 或从 OFF 到 ON。
• 当 switch 进行任何转换时，将触发回调并且可以检索新状态，即，可以根据该状态执行任何其他操作。
• 默认情况下，小部件的表示是静态的。所需的最小尺寸为 83*32 像素。
• 整个小部件都处于活动状态，而不仅仅是带有图形的部分。只要您在小部件的边界框上滑动，它就会起作用。

Basic Approach:

1) import kivy
2) import kivyApp
3) import Switch
4) import Gridlayout
5) import Label
6) Set minimum version(optional)
7) create Layout class(In this you create a switch):
        --> define the callback of the switch in this
8) create App class
9) create .kv file (name same as the app class):
        1) create boxLayout
        2) Give Label
        3) Create Switch
        4) Bind a callback if needed
10) return Layout/widget/Class(according to requirement)
11) Run an instance of the class

下面是实现：
我们已经解释了如何创建按钮、为其附加回调以及如何在使按钮处于活动/非活动状态后禁用按钮。
main.py 文件：

Python3

# Program to explain how switch works
 
# import kivy module  
import kivy
   
# base Class of your App inherits from the App class.  
# app:always refers to the instance of your application 
from kivy.app import App
 
# this restrict the kivy version i.e
# below this kivy version you cannot
# use the app or software
kivy.require('1.9.0')
 
# The Switch widget is active or inactive
# The state transition of a switch is from
# either on to off or off to on.
from kivy.uix.switch import Switch
 
# The GridLayout arranges children in a matrix.
# It takes the available space and
# divides it into columns and rows,
# then adds widgets to the resulting “cells”.
from kivy.uix.gridlayout import GridLayout
 
# The Label widget is for rendering text.
from kivy.uix.label import Label
 
# A Gridlayout with a label a switch
# A class which contains all stuff about the switch
class SimpleSwitch(GridLayout):
     
    # number of rows
    rows = 4
 
    # Callback for the switch state transition
    # Defining a Callback function
    # Contains Two parameter switchObject, switchValue
    def switch_callback(self, switchObject, switchValue):
         
        # Switch value are True and False
        if(switchValue):
            print('Switch is ON:):):)')
        else:
            print('Switch is OFF:(:(:(')
           
 
# Defining the App Class
class SwitchApp(App):
     # define build function
     def build(self):
          # return the switch class
          return SimpleSwitch()
 
  
# Run the kivy app
if __name__ == '__main__':
     SwitchApp().run()

.kv 文件：在此我们完成了回调并完成了按钮禁用。

Python3

# .kv file in which the whole functions of a switch
# Along with labels are present
 
:
 
    # creating box layout for better view
    BoxLayout:
        size_hint_y: None
        height: '48dp'
 
        # Adding label to switch
        Label:
            text: 'Switch normal'
 
        # creating the switch
        Switch:
 
            # False means OFF and True means ON
            active: False
             
            # Arranging a callback to the switch
            on_active: root.switch_callback(self, self.active)
 
    # Another for another switch
     
    BoxLayout:
        size_hint_y: None
        height: '48dp'
 
        Label:
            text: 'Switch active'
        Switch:
            active: True
            on_active: root.switch_callback(self, self.active)
 
 
    BoxLayout:
        size_hint_y: None
        height: '48dp'
 
        Label:
            text: 'Switch off & disabled'
             
        Switch:
            # disabled True means After making switch False
            # it is disabled now you cannot change its state
            disabled: True
            active: False
 
    BoxLayout:
        size_hint_y: None
        height: '48dp'
 
        Label:
            text: 'Switch on & disabled'
        Switch:
            disabled: True
            active: True

输出：
图 1：

图 2：

显示回调的图像：