How to use the kivy.app.App.get_running_app function in Kivy

def on_stop(*l):
            if self.modal:
                m = self._modal_view
                m.remove_widget(self)
                Window.remove_widget(m)
            Window.remove_widget(self)
            if self.exit:
                App.get_running_app().stop()
                import sys
                sys.exit()
            else:
                App.get_running_app().is_exit = False

def on_stop(*l):
            if self.modal:
                m = self._modal_view
                m.remove_widget(self)
                Window.remove_widget(m)
            Window.remove_widget(self)
            if self.exit:
                App.get_running_app().stop()
                import sys
                sys.exit()
            else:
                App.get_running_app().is_exit = False

def get_last_results(self):
        """
        Gets last rolls & results using pyetheroll lib and updates `roll_logs`
        list property.
        """
        # lazy loading
        from etherscan.client import ConnectionRefused
        controller = App.get_running_app().root
        account = controller.current_account
        if not account:
            controller.on_account_none()
            self.on_back()
            return
        self._fetching_results = True
        self.toggle_spinner(show=True)
        address = "0x" + account.address.hex()
        try:
            self.roll_logs = self.pyetheroll.get_merged_logs(
                address=address)
        except ConnectionRefused:
            self.on_connection_refused()
        self.toggle_spinner(show=False)
        self._fetching_results = False

def _change_action_view(self):
        app = App.get_running_app()
        action_bar = app.root.manager.current_screen.ids.action_bar
        _action_view = self.action_view

        if (not _action_view) or _action_view.parent:
            return
        action_bar.clear_widgets()
        action_bar.add_widget(_action_view)

def start_services():
        """
        Starts both roll polling service and OSC service.
        The roll polling service is getting the OSC server connection
        parameters so it can communicate to it.
        """
        app = App.get_running_app()
        osc_server, sockname = OscAppServer.get_or_create(app)
        server_address, server_port = sockname
        print(sockname)
        arguments = {
            'osc_server_address': server_address,
            'osc_server_port': server_port,
        }
        start_roll_polling_service(arguments)

def __init__(self, **kwargs):
        super(OutputList, self).__init__(**kwargs)
        self.app = App.get_running_app()  # type: ElectrumWindow

def get_game_info(self):
        gi = self.abstractboard.get_gameinfo()
        self.gameinfo = gi
        self.get_player_details()
        self.populate_sgf_model_gameinfo()
        try:
            print('Trying to remind')
            print((App.get_running_app().manager))
            print((App.get_running_app().manager.collections_to_refresh))
            App.get_running_app().manager.add_collection_refresh_reminder(
                self.sgf_model.name)
            print('Added collection refresh reminder')
            App.get_running_app().manager.homescreen_to_refresh = True
            print('Set homescreen refresh reminder')
        except AttributeError:
            print('Tried to refresh collectionsgf before it was created?')
        # try:

def __init__(self, widget):
        super(Controller, self).__init__()
        self.view = widget
        self.settings = kivy.app.App.get_running_app().settings
        kivy.app.App.get_running_app().main_widget = widget

        self.last_background_url = None  # Race condition prevention
        self.anim = None  # Race condition prevention

        # this effectively calls on_next_frame, when the view is ready
        Clock.schedule_once(self.on_next_frame, 0)

def on_width(self, instance, width):
        """When the width of the panel is changed, save to the app settings."""

        del instance
        if self.animating:
            return
        if width > 0:
            app = App.get_running_app()
            widthpercent = (width/Window.width)
            app.config.set('Settings', 'rightpanel', widthpercent)
        if self.hidden:
            self.width = 0

content_cancel = Button(text='Cancel', size_hint_y=None, height=40)
                 content.add_widget(Button(text='Reply'))
                 content.add_widget(Button(text='Forward'))
                 content.add_widget(Button(text='Select'))
                 content.add_widget(Button(text='Delete'))
                 content.add_widget(content_cancel)
                
                 popup = Popup(title='Test popup',
                               size_hint=(None, None), size=(256, 256),
                               content=content, disabled=False)
                 
                 content_cancel.bind(on_release=popup.dismiss)
                 popup.open()

                 # expose for unit testing
                 app = App.get_running_app()
                 app.message_control = content