kivy Using the Screen Manager Simple Screen Manager Usage

Example

# A line used mostly as the first one, imports App class
# that is used to get a window and launch the application
from kivy.app import App

# Casual Kivy widgets that reside in kivy.uix
from kivy.uix.label import Label
from kivy.uix.button import Button
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.uix.screenmanager import SlideTransition

# Inherit Screen class and make it look like
# a simple page with navigation

class CustomScreen(Screen):

    # It's necessary to initialize a widget the class inherits
    # from to access its methods such as 'add_widget' with 'super()'

    def __init__(self, **kwargs):
        # Py2/Py3 note: although in Py3 'super()' is simplified
        # it's a good practice to use Py2 syntax, so that the
        # code is compatibile in both versions
        super(CustomScreen, self).__init__(**kwargs)

        # Put a layout in the Screen which will take
        # Screen's size and pos.

        # The 'orientation' represents a direction
        # in which the widgets are added into the
        # BoxLayout - 'horizontal' is the default
        layout = BoxLayout(orientation='vertical')

        # Add a Label with the name of Screen
        # and set its size to 50px
        layout.add_widget(Label(text=self.name, font_size=50))

        # Add another layout to handle the navigation
        # and set the height of navigation to 20%
        # of the CustomScreen
        navig = BoxLayout(size_hint_y=0.2)

        # Create buttons with a custom text
        prev = Button(text='Previous')
        next = Button(text='Next')

        # Bind to 'on_release' events of Buttons
        prev.bind(on_release=self.switch_prev)
        next.bind(on_release=self.switch_next)

        # Add buttons to navigation
        # and the navigation to layout
        navig.add_widget(prev)
        navig.add_widget(next)
        layout.add_widget(navig)

        # And add the layout to the Screen
        self.add_widget(layout)

    # *args is used to catch arguments that are returned
    # when 'on_release' event is dispatched

    def switch_prev(self, *args):
        # 'self.manager' holds a reference to ScreenManager object
        # and 'ScreenManager.current' is a name of a visible Screen
        # Methods 'ScreenManager.previous()' and 'ScreenManager.next()'
        # return a string of a previous/next Screen's name
        self.manager.transition = SlideTransition(direction="right")
        self.manager.current = self.manager.previous()

    def switch_next(self, *args):
        self.manager.transition = SlideTransition(direction="right")
        self.manager.current = self.manager.next()
 

class ScreenManagerApp(App):

    # 'build' is a method of App used in the framework it's
    # expected that the method returns an object of a Kivy widget

    def build(self):
        # Get an object of some widget that will be the core
        # of the application - in this case ScreenManager
        root = ScreenManager()

        # Add 4 CustomScreens with name 'Screen <order>`
        for x in range(4):
            root.add_widget(CustomScreen(name='Screen %d' % x))

        # Return the object
        return root


# This is only a protection, so that if the file
# is imported it won't try to launch another App

if __name__ == '__main__':
    # And run the App with its method 'run'
    ScreenManagerApp().run()