Kivy 2021: Beginner’s Guide to the Screen Manager | Kivy Tutorial

Kivy is a popular open-source Python framework used for developing cross-platform applications. One of the key features of Kivy is its Screen Manager, which allows developers to easily switch between different screens or views in their application. This tutorial will guide you through the basics of working with the Kivy Screen Manager, and will help you get started with building your own multi-screen applications.

Step 1: Install Kivy
Before you can start using the Screen Manager, you need to install Kivy on your system. You can do this by running the following command in your terminal:

pip install kivy

Alternatively, you can also install Kivy using a package manager like pipenv or conda.

Step 2: Create a Kivy App
To start building your multi-screen application, you first need to create a Kivy App. Here is a simple example of a Kivy App that uses the Screen Manager:

from kivy.app import App
from kivy.uix.screenmanager import ScreenManager, Screen

class MyApp(App):

    def build(self):
        sm = ScreenManager()

        screen1 = Screen(name='screen1')
        screen1.add_widget(Label(text='Screen 1'))

        screen2 = Screen(name='screen2')
        screen2.add_widget(Label(text='Screen 2'))

        sm.add_widget(screen1)
        sm.add_widget(screen2)

        return sm

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

In this example, we create a Kivy App called MyApp that contains a ScreenManager and two Screen objects (screen1 and screen2). Each Screen object contains a Label widget with some text. Finally, we add the screens to the ScreenManager and return the ScreenManager from the build method.

Step 3: Switching Between Screens
To switch between screens in your application, you can use the switch_to() method of the ScreenManager class. Here is an example of how to switch from screen1 to screen2 in our Kivy App:

from kivy.uix.button import Button

class MyApp(App):

    def build(self):
        sm = ScreenManager()

        screen1 = Screen(name='screen1')
        screen1.add_widget(Button(text='Go to Screen 2', on_press=lambda x: sm.switch_to(screen2)))

        screen2 = Screen(name='screen2')
        screen2.add_widget(Button(text='Go to Screen 1', on_press=lambda x: sm.switch_to(screen1)))

        sm.add_widget(screen1)
        sm.add_widget(screen2)

        return sm

In this example, we have replaced the Label widgets with Button widgets that switch between the two screens when clicked.

Step 4: Adding Transitions
You can also add transitions between screens in your application to create a more visually appealing user experience. Kivy provides a range of built-in transitions that you can use with the ScreenManager class. Here is an example of how to add a slide transition between screens:

from kivy.uix.screenmanager import SlideTransition

class MyApp(App):

    def build(self):
        sm = ScreenManager(transition=SlideTransition())

        screen1 = Screen(name='screen1')
        screen1.add_widget(Button(text='Go to Screen 2', on_press=lambda x: sm.switch_to(screen2)))

        screen2 = Screen(name='screen2')
        screen2.add_widget(Button(text='Go to Screen 1', on_press=lambda x: sm.switch_to(screen1)))

        sm.add_widget(screen1)
        sm.add_widget(screen2)

        return sm

In this example, we have added a slide transition to the ScreenManager object to create a sliding animation when switching between screens.

Step 5: Customize Screens
You can customize the appearance of your screens by adding widgets and layouts to them. For example, you can create a screen with a grid layout containing multiple buttons:

from kivy.uix.gridlayout import GridLayout

class MyApp(App):

    def build(self):
        sm = ScreenManager()

        screen1 = Screen(name='screen1')
        layout = GridLayout(cols=2)
        layout.add_widget(Button(text='Button 1'))
        layout.add_widget(Button(text='Button 2'))
        screen1.add_widget(layout)

        screen2 = Screen(name='screen2')
        screen2.add_widget(Label(text='Screen 2'))

        sm.add_widget(screen1)
        sm.add_widget(screen2)

        return sm

In this example, we have replaced the Label widget in screen1 with a GridLayout containing two Button widgets.

Step 6: Advanced Usage
The Kivy Screen Manager provides a range of advanced features for building complex multi-screen applications. You can customize transitions, control screen ordering, and add screen references to easily switch between screens in your application. For more information on advanced usage of the Kivy Screen Manager, refer to the official Kivy documentation.

In conclusion, the Kivy Screen Manager is a powerful tool for creating multi-screen applications with Python and Kivy. By following this tutorial, you should be able to get started with using the Screen Manager in your own projects, and build engaging user interfaces with seamless screen transitions.