Kivy- Assign variables with on selection Recycleview

Question

I have a problem which may be quite python-ignorant rather than kivy problem.

I cant program kivy in python so I have KV file and py file.

I have modified Recycleview with SelectableLabel from kivy documentation. However, unlike all other widget, this one works differently.

This is main.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
from kivy.config import Config   
try:
    import kivy
except ImportError:
    raise ImportError("this backend requires Kivy to be installed.")


from kivy.uix.recycleview import RecycleView
from kivy.uix.recycleview.views import RecycleDataViewBehavior
from kivy.uix.label import Label
from kivy.properties import BooleanProperty
from kivy.uix.recycleboxlayout import RecycleBoxLayout
from kivy.uix.behaviors import FocusBehavior
from kivy.uix.recycleview.layout import LayoutSelectionBehavior

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout

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


class SelectableLabel(RecycleDataViewBehavior, Label):
    ''' Add selection support to the Label '''
    index = None
    selected = BooleanProperty(False)
    selectable = BooleanProperty(True)

    def refresh_view_attrs(self, rv, index, data):
        ''' Catch and handle the view changes '''
        self.index = index
        return super(SelectableLabel, self).refresh_view_attrs(
            rv, index, data)

    def on_touch_down(self, touch):
        ''' Add selection on touch down '''
        if super(SelectableLabel, self).on_touch_down(touch):
            return True
        if self.collide_point(*touch.pos) and self.selectable:
            return self.parent.select_with_touch(self.index, touch)

    def apply_selection(self, rv, index, is_selected):
        ''' Respond to the selection of items in the view. '''
        self.selected = is_selected
        self.change_this_variable = 'Here'
        """I wish to change this variable that belongs to MainWindow instance
        """
        if is_selected:
            print("selection changed to {0}".format(rv.data[index]))
        else:
            print("selection removed for {0}".format(rv.data[index]))



class MainWindow(BoxLayout):
    def __init__(self, *args, **kwargs):
        super(MainWindow, self).__init__(*args, **kwargs)
        self.change_this_variable = '' # Variable I want to change from 
        #                                select_event

        #My whole app logic is here
        #
        #

class guitApp(App):
    pass

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

Here is guit.kv

MainWindow:                                
    BoxLayout:

        RecycleView:
            id: rv
            data:[{'text': str(x)} for x in range(10)] # #
            viewclass: 'SelectableLabel'
            SelectableRecycleBoxLayout:
                id: slr
                default_size: None, dp(56)
                default_size_hint: 1, None
                size_hint_y: None
                height: self.minimum_height
                orientation: 'vertical'
                multiselect: False
                touch_multiselect: True


<SelectableLabel>:
    # Draw a background to indicate selection
    canvas.before:
        Color:
            rgba: (1, 0.866, .0, 1) if self.selected else (0, 0.419, 1,1)
        Rectangle:
            pos: self.pos
            size: self.size

My problem is, that I usually create widgets in kivy language, give it id and do logic in main.py via id reference or with on_event: root.function() in kivy lang. But with this SelecteableLabel and RecycleView from documentation, I am given on_event function called apply_selection but it is outside Gui Object(MainWindow, where all logic happens) so I cant access it. I dont want to solve this with Globals. So my question is, how to get apply_selection inside my Gui object so I can assign values to MainWindow's variables (like self.change_this_variable)?

Answer 1

There is no need to get apply_selection() method inside MainWindow(). The solution is to use App.get_running_app().root to get an instance of MainWindow() and you can reference its attributes and methods as follow:

Snippets

def apply_selection(self, rv, index, is_selected):
    ''' Respond to the selection of items in the view. '''
    self.selected = is_selected

    App.get_running_app().root.change_this_variable = 'Here'

    """I wish to change this variable that belongs to MainWindow instance
    """

    if is_selected:
        print("selection changed to {0}".format(rv.data[index]))
    else:
        print("selection removed for {0}".format(rv.data[index]))