Kivy callback custom widget call from ids raise AttributeError

Question

I'm trying to call a custom widget method from its ids.

But I received an AttributeError: 'LabelBox' object has no attribute 'change_first_text'.

As a simple as possible working example can be found here with the PanelApp.py file:

from kivy.app import App
from kivy.uix.tabbedpanel import TabbedPanel
from kivy.uix.boxlayout import BoxLayout
from kivy.lang import Builder

Builder.load_file("panel.kv")

class LabelBox(BoxLayout):
    def __init__(self, *args, **kwargs):
        super(LabelBox, self).__init__(*args, **kwargs)

    def change_first_text(self, text):
        self.ids.first.text = text

class ButtonList(BoxLayout):
    pass

class Test(TabbedPanel):
    pass


class TabbedPanelApp(App):
    def build(self):
        self.test = Test()
        self.btn_list = ButtonList()
        self.vbox = BoxLayout(orientation="vertical")
        self.vbox.add_widget(self.btn_list)
        self.vbox.add_widget(self.test)
        return self.vbox

    def change_first(self, value):
        print("Button clicked and new value is: '{}'".format(value))
        self.test.ids.lbs.change_first_text(value)


if __name__ == '__main__':
    TabbedPanelApp().run()

and the panel.kv file:

<ButtonList@ButtonList>:
    orientation: "horizontal"
    Button:
        text: "change fisrt to me"
        on_press: app.change_first(self.text)
    Button:
        text: "change two to me"

<LabelBox@BoxLayout>:
    Label:
        id: first
        text: "first"
    Label:
        id: two
        text: "two"

<Test>:
    size_hint: .5, .5
    pos_hint: {'center_x': .5, 'center_y': .5}
    do_default_tab: False

    TabbedPanelItem:
        text: 'first tab'
        LabelBox:
            id: lbs

Calling the script cause a runtime error that I can't understand. Have you any clue on how to manage such event callback through the application?

eyllanesc · Accepted Answer · 2018-05-18 13:44:02Z

2

The problem in your case is that you are creating 2 classes called LabelBox:

1.

class LabelBox(BoxLayout):
    def __init__(self, *args, **kwargs):
        super(LabelBox, self).__init__(*args, **kwargs)

    def change_first_text(self, text):
        self.ids.first.text = text

2.

<LabelBox@BoxLayout>:
    Label:
        id: first
        text: "first"
    Label:
        id: two
        text: "two"

I understand that you only want to have a class so it is appropriate to do the creation with the inheritance in the .py and only the implementation of children in the .kv. The solution is to change delete @BoxLayout in the .kv

<LabelBox>:
    Label:
        id: first
        text: "first"
    Label:
        id: two
        text: "two"

answered May 18, 2018 at 13:44

eyllanesc

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1 Comment

Elendil Over a year ago

Thanks! It's works. I totally missed the "details" of @BoxLayout in the .kv file used to create a new class. Spent hours looking for this issue :-(

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