Buttons in Kivy are used to perform actions when clicked. ".kv" file is used to design the button layout while Python handles the logic.
Example: In this example, a TextInput is added to a Kivy window to show how widgets are placed using a .kv file.
# main.py
from kivy.app import App
from kivy.uix.floatlayout import FloatLayout
class Main(FloatLayout):
pass
class Demo(App):
def build(self):
return Main()
Demo().run()
# demo.kv
<Main>:
TextInput:
text: "Enter name"
size_hint: .5, .2
pos_hint: {"center_x": .5, "center_y": .5}
Output
Syntax
Button(text="", size_hint=(x, y), pos_hint={}, on_press=function)
Parameters:
- text: label shown on the button
- size_hint: width and height (0 to 1)
- pos_hint: position using x, y, center_x, center_y
- on_press: function called when button is clicked
Examples
Example 1: In this example, a button is created using a .kv file and prints a message when clicked.
# main.py
from kivy.app import App
from kivy.uix.floatlayout import FloatLayout
class Main(FloatLayout):
def click(self):
print("Button clicked")
class Demo(App):
def build(self):
return Main()
Demo().run()
# demo.kv
<Main>:
Button:
text: "Click"
size_hint: .4, .2
pos_hint: {"center_x": .5, "center_y": .5}
on_press: root.click()
Output
Explanation:
- "Button" creates the button and text: "Click" shows label
- "size_hint" sets size and "pos_hint" centers the button
- on_press: root.click() runs click()
- print("Button clicked") shows output
Example 2: In this example, a colored button is displayed at the center of the screen.
# main.py
from kivy.app import App
from kivy.uix.floatlayout import FloatLayout
class Main(FloatLayout):
pass
class Demo(App):
def build(self):
return Main()
Demo().run()
# demo.kv
<Main>:
Button:
text: "Submit"
size_hint: .5, .2
pos_hint: {"center_x": .5, "center_y": .5}
background_color: 0, 1, 0, 1
Output
Explanation:
- background_color: 0,1,0,1 makes it green
- size_hint sets size and pos_hint centers the button
- return Main() displays it