How to move from one class to another in kivy

Question

I am trying to make an android application...I am trying to switch from menu to server or client according to user input...but i am not able to switch from one class to another...main thing which pissed me off is that print statement inside ServerScreen is working but other part is not working...don't know why

Code:---

import kivy
from kivy.app import App
from kivy.uix.widget import Widget
from kivy.uix.label import Label
from kivy.uix.button import Button
from kivy.uix.screenmanager import ScreenManager, Screen



class MenuScreen(Screen):


    def __init__(self, **kwargs):

        super(MenuScreen, self).__init__(**kwargs)


        def Server(instance):
            self.clear_widgets()
            self.add_widget(Label ( text = 'Inside server function'))

            server = ServerScreen()
            #return server
            #server.function()

        self.add_widget(Label ( text = 'What Type Of Service You Want...???'))

        button1 = Button(text = 'Server',size_hint = (None,None),pos = (0,0))
        self.add_widget(button1)
        button1.bind(on_press = Server)

        button2 = Button(text = 'Client',size_hint = (None,None),pos = (100,0))
        self.add_widget(button2)
        #button2.bind(on_press = Client)




class ServerScreen(Screen):

    def __init__(self, **kwargs):
        super(ServerScreen, self).__init__(**kwargs)
        print('Inside server screen')

        self.clear_widgets()
        self.add_widget(Label (text = 'Working As A Server'))
        print("Hellooooooooooo")


sm = ScreenManager()
sm.add_widget(MenuScreen(name='Menu'))
sm.add_widget(ServerScreen(name='Server'))
#sm.add_widget(ClientScreen(name='Client'))    

class FileApp(App):

    def build(self):

        #return Menu()

        return sm

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

In which part i am making mistake...please point out that part & provide how can i solve that...

Output--->
Inside server screen
Hellooooooooooo

Answer 1

Look at my solution inspired by this excellent comment from inclement : Kivy: Changing screens in screen manager with an on_press event

import kivy
from kivy.app import App
from kivy.uix.widget import Widget
from kivy.uix.label import Label
from kivy.uix.button import Button
from kivy.uix.screenmanager import ScreenManager, Screen




class MenuScreen(Screen):
    def switching_function(*args):
        global sm
        sm.current = 'Server'

    def __init__(self, **kwargs):

        super(MenuScreen, self).__init__(**kwargs)


#         def Server(instance):
#             self.clear_widgets()
#             self.add_widget(Label ( text = 'Inside server function'))
#             server = ServerScreen()
#             #return server
#             #server.function()

        self.add_widget(Label ( text = 'What Type Of Service You Want...???'))

        button1 = Button(text = 'Server',size_hint = (None,None),pos = (0,0))
        self.add_widget(button1)
#         button1.bind(on_press = Server)
        button1.bind(on_press = self.switching_function)

        button2 = Button(text = 'Client',size_hint = (None,None),pos = (100,0))
        self.add_widget(button2)
        #button2.bind(on_press = Client)




class ServerScreen(Screen):

    def __init__(self, **kwargs):
        super(ServerScreen, self).__init__(**kwargs)
        print('Inside server screen')

        self.clear_widgets()
        self.add_widget(Label (text = 'Working As A Server'))
        print("Hellooooooooooo")


sm = ScreenManager()
sm.add_widget(MenuScreen(name='Menu'))
sm.add_widget(ServerScreen(name='Server'))
#sm.add_widget(ClientScreen(name='Client'))    

class FileApp(App):

    def build(self):

        #return Menu()

        return sm

The problem is with server = ServerScreen() inside

   def Server(instance):
        self.clear_widgets()
        self.add_widget(Label ( text = 'Inside server function'))
        server = ServerScreen()
        #return server
        #server.function()

It creates a new ServerScreen, not the ServerScreen which is actually displayed at the moment (so

Inside server screen
Hellooooooooooo

is displayed, but the ScreenManager has no idea that this additional Screen is existing.