Button Action in Kivy Python (original) (raw)

Last Updated : 9 Oct, 2025

A Button Action refers to attaching functionality to a button so that something happens when the button is pressed or released. Instead of just displaying a button, we define callbacks that update labels, print messages, toggle states or perform any other action.

This example creates a simple button that prints a message when pressed.

Python `

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

class BasicButtonApp(App): def build(self): btn = Button(text="Click Me!")

    def on_press_action(instance):
        print("Button clicked!")
    
    btn.bind(on_press=on_press_action)
    return btn

if name == "main": BasicButtonApp().run()

`

**Output

Basic Button

**Explanation:

• **Button(text="Click Me!"): Creates a button with the specified label.
• **btn.bind(on_press=on_press_action): Binds the function to run when the button is pressed.
• **on_press_action(instance): Callback function printing the message.

Syntax

Button(text="Label", size_hint=(w,h), pos=(x,y), background_color=(r,g,b,a))

**Parameters:

• **text: Label displayed on the button.
• **size_hint: Fractional width and height relative to parent (use (None, None) for fixed size).
• **pos: Position of the button (requires fixed size).
• **background_color: Color of the button (RGBA).
• **on_press/on_release: Functions to execute when button is pressed or released.

Examples

**Example 1: This code updates a label when the button is pressed.

Python `

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

class LabelUpdateApp(App): def build(self): root = BoxLayout(orientation="vertical") lbl = Label(text="Not clicked") btn = Button(text="Press Me", size_hint=(1,0.3))

    def on_press_action(instance):
        lbl.text = "Button Pressed!"
    
    btn.bind(on_press=on_press_action)
    root.add_widget(lbl)
    root.add_widget(btn)
    return root

if name == "main": LabelUpdateApp().run()

`

**Output

Label Button

**Explanation:

• **BoxLayout(orientation="vertical"): Arranges widgets vertically.
• **lbl.text = "Button Pressed!": Updates the label dynamically.
• **btn.bind(on_press=on_press_action): Calls the function when button is pressed.

**Example 2: This example demonstrates two buttons, each performing a separate action when clicked.

Python `

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

class MultiButtonApp(App): def build(self): root = BoxLayout(orientation="vertical", spacing=10)

    def say_hello(instance):
        print("Hello!")
    
    def say_bye(instance):
        print("Goodbye!")
    
    btn1 = Button(text="Hello")
    btn2 = Button(text="Goodbye")
    btn1.bind(on_press=say_hello)
    btn2.bind(on_press=say_bye)
    
    root.add_widget(btn1)
    root.add_widget(btn2)
    return root

if name == "main": MultiButtonApp().run()

`

**Output

Multi Button

**Explanation:

• **BoxLayout(orientation="vertical", spacing=10): Stacks buttons vertically with spacing.
• Each button has an independent callback using **bind(on_press=...).
• Actions are executed when respective buttons are pressed.