In Kivy, the BoxLayout class is used to arrange widgets in either a horizontal or vertical layout. It provides a simple way to organize your UI elements in a linear fashion.

To use the BoxLayout class, you first need to import it from the kivy.uix module:

from kivy.uix.boxlayout import BoxLayout

Next, create an instance of the BoxLayout class and add your widgets to it. The BoxLayout can be created with the parameter orientation set to either “horizontal” or “vertical”:

layout = BoxLayout(orientation='horizontal')

Adding Widgets

To add widgets to the BoxLayout, use the add_widget() method. This method adds the widgets to the end of the layout, preserving their order:

layout.add_widget(widget1)
layout.add_widget(widget2)
layout.add_widget(widget3)

Widget Alignment

By default, the BoxLayout centers its children widgets along the main axis. You can adjust the alignment using the alignment property. The alignment property accepts values like “left”, “right”, “top”, “bottom”, “center”, “justify”, etc.

layout.alignment = 'center'

Spacing

The BoxLayout also allows you to control the spacing between its children widgets using the spacing property. The spacing property specifies the number of pixels between widgets.

layout.spacing = 10

Example

Here’s a simple example that demonstrates the usage of BoxLayout:

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.button import Button


class MyBoxLayout(App):
    def build(self):
        layout = BoxLayout(orientation='horizontal', spacing=10)
        button1 = Button(text='Button 1')
        button2 = Button(text='Button 2')
        button3 = Button(text='Button 3')
        layout.add_widget(button1)
        layout.add_widget(button2)
        layout.add_widget(button3)
        return layout


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

In this example, we create a simple App with a BoxLayout containing three buttons. The BoxLayout is set to a horizontal orientation and each button has a spacing of 10 pixels between them.

The BoxLayout is a powerful layout manager that helps you create clean and organized UIs in Kivy. Experiment with different orientations, alignments, and spacings to achieve the desired layout for your application.