Cannot add DropDown object at 0x000002D18787E6C0 to window, it already has a parent

Question

I've coded this little app with Kivy that has 3 textbox + 1 dropdown:

from kivy.app import App
from kivy.uix.gridlayout import GridLayout
from kivy.uix.textinput import TextInput
from kivy.uix.dropdown import DropDown
from kivy.uix.button import Button
from kivy.uix.label import Label
from kivy.uix.popup import Popup

class Inremapp(App):
    def AddDropDownButton(self, name):
        self.btn = Button(text=name, size_hint_y=None, height=44)
        self.btn.bind(on_release=lambda btn: self.dropdown.select(self.btn.text))
        self.dropdown.add_widget(self.btn)

    def build(self):
        self.operaciones = ["1", "123", "1241", "124121"]
        self.window = GridLayout()
        self.window.cols = 1
        self.window.size_hint = (0.6, 0.7)
        self.window.pos_hint = {"center_x": 0.5, "center_y":0.5}    
        
        # entrada
        labelentrada = Label(text='Entrada: (Día/Mes/Año)')
        self.window.add_widget(labelentrada)
        txtinday = TextInput(text='', multiline=False)
        self.window.add_widget(txtinday)

        # salida
        labelsalida = Label(text='Salida: (Día/Mes/Año)')
        self.window.add_widget(labelsalida)
        txtoutday = TextInput(text='', multiline=False)
        self.window.add_widget(txtoutday)

        # obra
        txtobra = TextInput(text='Obra', multiline=False)
        self.window.add_widget(txtobra)

        # operación
        self.dropdown = DropDown()
        for operacion in self.operaciones:
            self.AddDropDownButton(operacion)
        mainbutton = Button(text='Operación')
        mainbutton.bind(on_release=self.dropdown.open)
        self.dropdown.bind(on_select=lambda instance, x: setattr(mainbutton, 'text', x))
        self.window.add_widget(self.dropdown)
        self.window.add_widget(mainbutton)

        return self.window

# run app
if __name__ == "__main__":
    Inremapp().run()

The app looks like this when running:

But when I click the dropdown button I get the following error:

Exception has occurred: WidgetException Cannot add to window, it already has a parent File "D:\Inrema\TabletConnect\main.py", line 68, in Inremapp().run()

The basic example from Kivy docs is working fine but... what I'm missing in my code?

EDIT:

After removing self.window.add_widget(self.dropdown) error disappeared, dropdown is showing up but when I select any element I will always get the latest value, doesn't matters what I select.

EDIT 2:

Changed this line:

self.btn.bind(on_release=lambda btn: self.dropdown.select(self.btn.text))

To this:

self.btn.bind(on_release=lambda btn: self.dropdown.select(btn.text))

And worked fine :)

Cannot add DropDown object at 0x000002D18787E6C0> to window, it already has a parent

0 Answers