id not being passed to filechooser - python-3.x

Question

I have attached an image showing that the correct filechooser path is being printed out to the console when selecting the file. From that, I assume that the problem is that the self.ids.image.source = filename[0] is failing. Specifically, the id referencing the Image.source. I have tried changing the id and referencing the new one. That doesn't work. I'm still learning Kivy, so I'm not sure if I messed up the hierarchy and I should be calling another id to reference the filechooser's.
Also, I deleted two MDBottomNavigationItems and the contents of the other screens to clean up the code. The question is referring to the LibraryWindow screen.
py file
from kivy.lang import Builder
from kivymd.app import MDApp
from kivy.uix.screenmanager import Screen
from kivy.uix.boxlayout import BoxLayout
# Screens
class LibraryWindow(Screen):
pass
class PlayingWindow(Screen):
pass
class VisualWindow(Screen):
pass
# Top Action Bar
class TopBar(BoxLayout):
pass
# App
class MainApp(MDApp):
def build(self):
self.theme_cls.theme_style = "Dark"
self.theme_cls.primary_palette = "BlueGray"
return Builder.load_file('Z:\\PycharmProjects\\kivyMD\\venv\\my.kv')
def selected(self, filename):
try:
print(filename[0])
self.ids.image.source = filename[0]
except:
pass
MainApp().run()
Kv outline
BoxLayout:
orientation: 'vertical'
TopBar:
MDBottomNavigation:
MDBottomNavigationItem:
name: 'navlib'
text: "Library"
icon: 'book'
LibraryWindow:
#############################
### S C R E E N S ###
#############################
<LibraryWindow>:
name: "library"
size: root.width, root.height
id: my_widget
canvas.before:
Color:
rgba: 0.5,0,0,1
Rectangle:
size: self.size
BoxLayout:
orientation: "vertical"
size: root.width, root.height
padding: 50
spacing: 20
Image:
id: image
source: ''
FileChooserIconView:
id: filechooser
color: 1,.3, .3, 1
on_selection: app.selected(filechooser.selection)
<PlayingWindow>:
<VisualWindow>:
<TopBar>:

Answer 1

Setting an id on the widget that is the root of a rule will not work. The ids are only assigned for children of the widget that is the root of the rule.
Note that the kivy lang documentation confuses the term root widget, using that term for both the root widget of the app and the root widget of a rule. The ids are only set in the ids dictionary of the widget that is the root of the rule where the id appears.
So, you can access the Image widget by adding an id to the LibraryWindow instance in the BoxLayout (the one that is the root of the app) like this:
BoxLayout:
orientation: 'vertical'
TopBar:
MDBottomNavigation:
MDBottomNavigationItem:
name: 'navlib'
text: "Library"
icon: 'book'
LibraryWindow:
id: library
Then you code to set the Image source can become:
self.root.ids.library.ids.image.source = filename[0]
The self.root gets the root widget of the app. The ids.library gets the LibraryWindow instance. The ids.image gets the Image instance that has the image id.