Problem with changing the value of main button in KivyMD Menu - oop

Question

I have created a KivyMD Menu. When I click on the main Button, the menu is opening without a problem. However when I click on a menu button the value of the main button is not changing. Nothing happens. I thought the code is sufficient to achieve it. Does anyone know a solution? Thank you in advance!
py file:
from kivy.core.window import Window
from kivy.uix.screenmanager import Screen
from kivy.lang import Builder
from kivymd.app import MDApp
from kivymd.uix.menu import MDDropdownMenu
Window.size = (400, 800)
class homescreen(Screen):
pass
GUI = Builder.load_file("main.kv")
class MainApp(MDApp, homescreen):
def __init__(self, **kwargs):
super().__init__(**kwargs)
self.homescreen = Builder.load_string("homescreen")
menu_items = [{"icon": "git", "text": f"Item {i}"} for i in range(5)]
self.menu = MDDropdownMenu(
caller=self.ids.drop_item,
items=menu_items,
#position="center",
width_mult=4,
)
self.menu.bind(on_release=self.set_item)
def set_item(self, instance_menu, instance_menu_item):
self.ids.drop_item.set_item(instance_menu_item.text)
self.menu.dismiss()
def build(self):
return self.homescreen
if __name__ == "__main__":
MainApp().run()
main.kv:
<homescreen>:
MDDropDownItem:
id: drop_item
pos_hint: {'center_x': .5, 'center_y': .5}
text: "Select"
on_release: app.menu.open()

Answer 1

Here is your improved code
py file:
from kivy.core.window import Window
from kivy.uix.screenmanager import Screen
from kivy.lang import Builder
from kivymd.app import MDApp
from kivymd.uix.menu import MDDropdownMenu
Window.size = (400, 800)
class homescreen(Screen):
pass
GUI = Builder.load_file("main.kv")
class MainApp(homescreen):
def __init__(self, **kwargs):
super().__init__(**kwargs)
self.homescreen = Builder.load_string("homescreen")
menu_items = [{"icon": "git", "text": f"Item {i}"} for i in range(5)]
self.menu = MDDropdownMenu(
caller=self.ids.drop_item,
items=menu_items,
callback=self.set_item,
width_mult=4,
)
def set_item(self, instance_menu_item):
self.ids.drop_item.text = instance_menu_item.text
self.menu.dismiss()
def build(self):
return self.homescreen
class app(MDApp):
def build(self):
return MainApp()
if __name__ == "__main__":
app().run()
main.ky
<homescreen>:
MDDropDownItem:
id: drop_item
pos_hint: {'center_x': .5, 'center_y': .5}
text: "Select"
on_release: root.menu.open()