main.py

from kivy.app import App

from kivy.uix.label import Label
from kivy.uix.button import Button
from kivy.uix.listview import ListItemButton

from kivy.uix.boxlayout import BoxLayout

from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.properties import ObjectProperty

class StatusBar(BoxLayout):
    pass
class TabBar(BoxLayout):
    pass
class Content(ListItemButton):
    pass
class Drawer(BoxLayout):
    pass
class Page(Screen):
    pass
class MainScreen(Page):
    pass
class LoginScreen(Page):
    pass
class HistoryScreen(Page):
    pass
class OverviewScreen(Page):
    pass
class PlotScreen(Page):
    pass

screenmanager=ScreenManager()
screenmanager.add_widget(MainScreen(name='mainscreen'))
screenmanager.add_widget(LoginScreen(name='loginscreen'))
screenmanager.add_widget(HistoryScreen(name='historyscreen'))
screenmanager.add_widget(OverviewScreen(name='overviewscreen'))
screenmanager.add_widget(PlotScreen(name='plotscreen'))

class MainApp(App):
    def build(self):
        return screenmanager
MainApp().run()