Unknown class error even if class is defined Kivy/recycle view

Question

I have this snippet from my design.kv file:

<Track>:
    on_release:
        root.print_data(self.text)

RecycleView:
    viewclass: 'Track'
    RecycleGridLayout:
        cols: 1
        default_size_hint: 1, None
        orientation: 'vertical'

However it returns an error:

The class 'Track was defined as seen in the snippet above as well as in my python code.

I tried setting the viewclass to 'Button' and it worked but it just returned a button which is not the intended behavior.

What am I getting wrong here? Thanks :)

The whole code of my python and kivy files are right here: https://github.com/Jezrianne/ANTS

Just in case the error does not originate from the snippet above :)

Answer 1

Root Widget - Screen

The following example illustrates using Screen widget as the root widget and combined with RecycleView widget.

main.py

from kivy.app import App
from kivy.uix.recycleview.views import RecycleDataViewBehavior
from kivy.uix.recyclegridlayout import RecycleGridLayout
from kivy.uix.behaviors import FocusBehavior
from kivy.uix.recycleview.layout import LayoutSelectionBehavior
from kivy.uix.button import Button
from kivy.uix.screenmanager import Screen
from kivy.lang import Builder


Builder.load_string('''
#:kivy 1.11.0

<Track>:
    on_release:
        root.print_data(self.text)

<RootWidget>:
    RecycleView:
        id: rv
        viewclass: 'Track'
        SelectableRecycleGridLayout:
            cols: 1
            default_size: None, dp(56)
            default_size_hint: 1, None
            size_hint_y: None
            height: self.minimum_height
            orientation: 'vertical'
            multiselect: True
            touch_multiselect: True
''')


class Track(RecycleDataViewBehavior, Button):

    def print_data(self, text):
        print("\nprint_data: text=", text)


class SelectableRecycleGridLayout(FocusBehavior, LayoutSelectionBehavior,
                                  RecycleGridLayout):
    ''' Adds selection and focus behaviour to the view. '''


class RootWidget(Screen):
    def __init__(self, **kwargs):
        super(RootWidget, self).__init__(**kwargs)
        self.ids.rv.data = [{'text': str(x)} for x in range(100)]


class TestApp(App):
    def build(self):
        return RootWidget()


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

Root Widget - RecycleView

There is no attribute, orientation: for GridLayout. Please remove it from your kv file.

You need to implement the following:

Snippet

class Track(RecycleDataViewBehavior, Button):

    def print_data(self, text):
        print("\nprint_data: text=", text)


class SelectableRecycleGridLayout(FocusBehavior, LayoutSelectionBehavior,
                                  RecycleGridLayout):
    ''' Adds selection and focus behaviour to the view. '''

Example

main.py

from kivy.app import App
from kivy.uix.recycleview import RecycleView
from kivy.uix.recycleview.views import RecycleDataViewBehavior
from kivy.uix.recyclegridlayout import RecycleGridLayout
from kivy.uix.behaviors import FocusBehavior
from kivy.uix.recycleview.layout import LayoutSelectionBehavior
from kivy.uix.button import Button


class Track(RecycleDataViewBehavior, Button):

    def print_data(self, text):
        print("\nprint_data: text=", text)


class SelectableRecycleGridLayout(FocusBehavior, LayoutSelectionBehavior,
                                  RecycleGridLayout):
    ''' Adds selection and focus behaviour to the view. '''


class RV(RecycleView):
    def __init__(self, **kwargs):
        super(RV, self).__init__(**kwargs)
        self.data = [{'text': str(x)} for x in range(100)]


class TestApp(App):
    def build(self):
        return RV()

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

test.kv

#:kivy 1.11.0

<Track>:
    on_release:
        root.print_data(self.text)

<RV>:
    viewclass: 'Track'
    SelectableRecycleGridLayout:
        cols: 1
        default_size: None, dp(56)
        default_size_hint: 1, None
        size_hint_y: None
        height: self.minimum_height
        orientation: 'vertical'
        multiselect: True
        touch_multiselect: True

Output