How can I modify the title of the MDTopAppBar when a button, located in a separate class, is clicked? - kivy

Question

How can I modify the title of the MDTopAppBar in response to a user selecting a button within the NavigationDrawer, such as updating the title to match the selected button's label (e.g. "Coffee")?
main.py
from kivy.lang import Builder
from kivy.properties import ObjectProperty
from kivy.uix.screenmanager import ScreenManager, Screen
from kivymd.app import MDApp
from kivymd.uix.scrollview import MDScrollView
class MainLayout(Screen):
pass
class NavigationDrawer(MDScrollView):
screen_manager = ObjectProperty()
nav_drawer = ObjectProperty()
class App(MDApp):
def build(self):
self.theme_cls.primary_palette = "Green"
self.theme_cls.theme_style = "Light"
kivy_layout = Builder.load_file("layout.kv")
return MainLayout()
if __name__ == "__main__":
App().run()
layout.kv
<NavigationDrawer>
MDNavigationDrawerMenu:
MDNavigationDrawerHeader:
title: "MyApp"
text: "Bottom Text"
source: "icon64.png"
spacing: "10dp"
MDNavigationDrawerDivider:
MDNavigationDrawerItem:
text: "Coffee"
icon: "coffee"
on_press:
root.nav_drawer.set_state("close")
root.screen_manager.current = "scr 1"
MDNavigationDrawerItem:
text: "History"
icon: "history"
on_press:
root.nav_drawer.set_state("close")
root.screen_manager.current = "scr 2"
MDNavigationDrawerItem:
text: "Settings"
icon: "cog"
on_press:
root.nav_drawer.set_state("close")
root.screen_manager.current = "scr 3"
MDNavigationDrawerDivider:
<MainLayout>
MDScreen:
MDTopAppBar:
id: top
title: "Title"
pos_hint: {"top": 1}
elevation: 4
left_action_items: [["menu", lambda x: nav_drawer.set_state("open")]]
MDNavigationLayout:
MDScreenManager:
id: screen_manager
MDScreen:
name: "scr 1"
MDLabel:
text: "Coffee"
halign: "center"
MDScreen:
name: "scr 2"
MDLabel:
text: "History"
halign: "center"
MDScreen:
name: "scr 3"
MDLabel:
text: "Settings"
halign: "center"
MDNavigationDrawer:
id: nav_drawer
radius: (0, 16, 16, 0)
NavigationDrawer:
screen_manager: screen_manager
nav_drawer: nav_drawer
After attempting to resolve the issue on my own through various means, including attempting to create a solution and conducting research online for potential solutions, I was unable to find a satisfactory resolution. As a result, I have determined it necessary to seek assistance through this platform.

Answer 1

You need to add an id to the MDNavigationDrawerHeader so you can access it from the class.
MDNavigationDrawerHeader:
id: drawer_header
title: "MyApp"
text: "Bottom Text"
source: "icon64.png"
spacing: "10dp"
Then you need to add a method to the NaviagtionDrawer class to make the update. You will access your NavDrawer Title by calling self.ids.drawer_header.title
class NavigationDrawer(MDScrollView):
screen_manager = ObjectProperty()
nav_drawer = ObjectProperty()
def set_title(self, title):
self.ids.drawer_header.title = title
Finally, you need to tell each button to call the set_title method that I created to actually do the update.
MDNavigationDrawerItem:
text: "Coffee"
icon: "coffee"
on_press:
root.nav_drawer.set_state("close")
root.set_title(self.text)
root.screen_manager.current = "scr 1"
To change the MDTopAppBar title add the following line to each of the on_press events:
app.change_title(self.text) # call method in main app
ie.
on_press:
root.nav_drawer.set_state("close")
root.set_title(self.text)
root.screen_manager.current = "scr 1"
app.change_title(self.text) # call method in main app
Then add the following method to your main app.
def change_title(self, title):
self.root.ids.top.title = title
ie.
def build(self):
self.theme_cls.primary_palette = "Green"
self.theme_cls.theme_style = "Light"
Builder.load_file("layout.kv")
return MainLayout()
def change_title(self, title):
self.root.ids.top.title = title