Kivy: how to update a label when a button is clicked - kivy

Question

I use a button to retrieve the paths of some folders selected with the filechooser. When the button is clicked I would like to update the text of the label so that it dispays the selected paths.
In my Kv:
Button:
text:'OK'
on_press: root.selected(filechooser.path, filechooser.selection)
Label:
id: Lb_ListViewFolder
text: root.Lb_ListViewFolder_text
color: 0, 0, 0, 1
size_hint_x: .75
In .py:
class MyWidget(BoxLayout):
Lb_ListViewFolder_text = ObjectProperty("Text")
def selected(self, a, b):
global Lb_ListViewFolder_text
Lb_ListViewFolder_text = b
print(a,b)
This doesn't give me any error but the label text isn't changed.
I also tried self.ListViewFolder.text = b like recommended here but I get this error: MyWidget' object has no attribute 'Lb_ListViewFolder'.
I have seen this answer, but I have trouble applying in my code
I use python 3.6 and Kivy 1.9.2.dev0
In case, this is my entire code:
from kivy.properties import ObjectProperty
from kivy.core.window import Window
from kivy.event import EventDispatcher
from kivy.lang import Builder
root = Builder.load_string('''
<MyWidget>
id: BL_Main
orientation: "horizontal"
padding: 10
spacing: 10
BoxLayout:
id: BL_folder
orientation: "vertical"
Button:
id:ok
text:'OK'
background_color: 0,0,1,1
height: 5
size_hint: 0.1, 0.1
on_press: root.selected(filechooser.path, filechooser.selection)
BoxLayout:
orientation:"horizontal"
size_hint: None, 0.9
width:150
canvas.before:
Color:
rgb: .4,.5,.5
Rectangle:
pos: self.pos
size: self.size
## multiple select folder not possible with FileChooserListView
FileChooserIconView:
id: filechooser
pos:self.pos
multiselect: True
dirselect: True
Label:
id: Lb_ListViewFolder
text: root.Lb_ListViewFolder_text
color: 0, 0, 0, 1
size_hint_x: .75
''')
class MyWidget(BoxLayout):
Lb_ListViewFolder_text = ObjectProperty("Text")
def selected(self, a, b):
global Lb_ListViewFolder_text
Lb_ListViewFolder_text = b
print(a,b)
class MyApp(App):
def build(self):
Window.clearcolor = (1, 1, 1, 1)
return MyWidget()
MyApp().run()

Answer 1

You can use StringProperty here:
from kivy.app import App
from kivy.uix.filechooser import FileChooserListView
from kivy.uix.boxlayout import BoxLayout
from kivy.lang import Builder
from kivy.properties import StringProperty
Builder.load_string('''
<MyLayout>:
orientation: "vertical"
Label:
text: root.label_text
Button:
id:ok
text:'OK'
on_press: root.selected(filechooser.path, filechooser.selection)
FileChooserIconView:
id: filechooser
pos:self.pos
multiselect: True
dirselect: True
''')
class MyLayout(BoxLayout):
label_text = StringProperty("File name")
def selected(self, a, b):
self.label_text = b[0]
class MyApp(App):
def build(self):
return MyLayout()
MyApp().run()
Or you can change it directly in kvlang:
<MyLayout>:
orientation: "vertical"
Label:
id: dirlabel
text: root.label_text
Button:
id:ok
text:'OK'
on_press: dirlabel.text = filechooser.selection[0]
FileChooserIconView:
id: filechooser
pos:self.pos
multiselect: True
dirselect: True