Animated Floating Action Button in kivy – Python

Kivy is a platform independent GUI tool in Python. As it can be run on Android, IOS, linux and Windows etc. It is basically used to develop the Android application, but it does not mean that it can not be used on Desktops applications.
In this article we will learn about how can we Add the Animation to a Floating Action button. To learn How to create it you must know about the Animation and Clock.

Animation : Animation and AnimationTransition are used to animate Widget properties. You must specify at least a property name and target value. To use an Animation, follow these steps:

• Setup an Animation object
• Use the Animation object on a Widget

To animate a Widget’s x or y position, simply specify the target x/y values where you want the widget positioned at the end of the animation: 

anim = Animation(x=100, y=100)
anim.start(widget)

Clock: The Clock object allows you to schedule a function call in the future; once or repeatedly at specified intervals.
It is must to use kivy inbuilt module while working with Animation and clock – 

from kivy.animation import Animation
from kivy.clock import Clock

Basic Approach:

1) import kivy
2) import kivyApp
3) import Boxlayout
4) import Animation
5) Import Clock
6) Set minimum version(optional)
7) create Layout class and Add(create) animation in it
8) create App class
9) Set up .kv file :
       1) Add Floating Button Properties
       2) Create Main Window
       3) Add Float Button(don't forget to give id)
10) return Layout/widget/Class(according to requirement)
11) Run an instance of the class

Kivy Tutorial – Learn Kivy with Examples.

Implementation of the Approach:
main.py file

Python3

## Sample Python application demonstrating that
## How to create a button like floating Action Button
## in Kivy using .kv file

###################################################
# import modules

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

# BoxLayout arranges widgets in either
# in a vertical fashion that
# is one on top of another or in a horizontal
# fashion that is one after another.
from kivy.uix.boxlayout import BoxLayout

# To change the kivy default settings
# we use this module config
from kivy.config import Config

# 0 being off 1 being on as in true / false
# you can use 0 or 1 && True or False
Config.set('graphics', 'resizable', True)

# The Clock object allows you to
# schedule a function call in the future
from kivy.clock import Clock

# To work with Animation you must have to import it
from kivy.animation import Animation

# creating the root widget used in .kv file
class MainWindow(BoxLayout):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)

        # Schedule the interval for the animation
        Clock.schedule_interval(self.breath, 1)

    # Creating Animation function name breath
    def breath(self, dtx):

        # create an animation object. This object could be stored
        # and reused each call or reused across different widgets.
        # += is a sequential step
        anim = (Animation(btn_size =(60, 60), t ='in_quad', duration =.5)+
               Animation(btn_size =(70, 70), t ='in_quad', duration =.5))

        # Call the button id
        tgt = self.ids.cta

        # Start the Animation
        anim.start(tgt)


# creating the App class in which name
#.kv file is to be named main.kv
class MainApp(App):
    # defining build()
    def build(self):
        # returning the instance of root class
        return MainWindow()

# run the app
if __name__ == '__main__':
    MainApp().run()

.kv file

Python3

#.kv file implementation of BoxLayout


# using Float Layout for the creation of Floatbutton
# Here we are creating the properties of button
# Button will be created in Main window Box Layout

<FloatButton@FloatLayout>
    id: float_root  # Giving id to button
    size_hint: (None, None)
    text: ''
    btn_size: (70, 70)
    size: (70, 70)
    bg_color: (0.404, 0.227, 0.718, 1.0)
    pos_hint: {'x': .6}

    # Adding shape and all, size, position to button
    Button:
        text: float_root.text
        markup: True
        font_size: 40
        size_hint: (None, None)
        size: float_root.btn_size
        pos_hint: {'x': 5.5, 'y': 3.8}
        background_normal: ''
        background_color: (0, 0, 0, 0)
        canvas.before:
            Color:
                rgba: (0.404, 0.227, 0.718, 1.0)
            Ellipse:
                size: self.size
                pos: self.pos

# Creation of main window
<MainWindow>:
    BoxLayout:
        # Creating the Float button
        FloatButton:

            # Giving id to the button
            # So that we can Apply the Animation
            id: cta
            text: '+'
            markup: True
            background_color: 1, 0, 1, 0

Output:

Video Output: