How can I use the RecycleView of Kivy on kv language with ScreenManager?

Question

I have a database on Firebase of Google working well, I can save my data there easily. I would like to return this data for my app, but before I have problems with this, I can't list anything on Kivy.

I would want to use the ListView of Kivy, but in the documentation is recommended to use the RecycleView. But I can't understand the documentation. I have some doubts.

If you can read the docs of RecycleView, you'll see this as an example:

Builder.load_string('''
<RV>:
    viewclass: 'Label'
    RecycleBoxLayout:
        default_size: None, dp(56)
        default_size_hint: 1, None
        size_hint_y: None
        height: self.minimum_height
        orientation: 'vertical'
''')

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()

But I'm using the ScreenManager to control my screens, then, in the TestApp class I return 'sm', like this example of the documentation:

# Declare both screens
class MenuScreen(Screen):
    pass

class SettingsScreen(Screen):
    pass

# Create the screen manager
sm = ScreenManager()
sm.add_widget(MenuScreen(name='menu'))
sm.add_widget(SettingsScreen(name='settings'))

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

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

If you see the syntaxes are different, and it's here where I don't know how to code this. I would like to keep using the ScreenManager to control the screens and use a RecycleView to return my data in a list.

How can I use the RecycleView with my ScreenManager? This is my main.py, I configure the screen in another document, and I use the ki language too. So if you all can to do an example to me I will be grateful.

import kivy
from kivy.app import App, Builder
from kivy.config import Config
from kivy.uix.screenmanager import ScreenManager
from telas.telas import Acesso, Comprando, Vendendo, CadastrarEvento


kivy.require('1.10.1')
Builder.load_file('ing.kv')
Config.read('config.ini')
sm = ScreenManager()

sm.add_widget(Acesso(name='acesso'))
sm.add_widget(Comprando(name='comprando'))
sm.add_widget(Vendendo(name='vendendo'))
sm.add_widget(CadastrarEvento(name='cadastrarEvento'))
sm.add_widget(ListaEventos(name='listaEventos'))

class IngApp(App):
    def build(self):
        return sm

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

Here the kv that I tried the first time

<ListaEventos>:
    canvas:
        Rectangle:
            source: 'design/fundo.png'
            size: self.width, self.height    


    viewclass: 'Label'
    RecycleBoxLayout:
        default_size: None, dp(56)
        default_size_hint: 1, None
        size_hint_y: None
        height: self.minimum_height
        orientation: 'vertical'

ListaEventos:

class ListaEvento(Screen, RecycleView):
    def __init__(self, **kwargs):
        super(ListaEvento, self).__init__(**kwargs)
        self.data = [{'text': str(x)} for x in range(20)]

And why have not you tried anything? Is that Screen going to be the RecyclerView? What data will be shown in that RecyclerView? Will the same data be used in the example? — eyllanesc, Sep 11 '18 at 01:11
but I tried. I can't use the example too, so I think in to begin with this (the example of documentation). In future, I want to show data of my Firebase, like a field or two, with name and date, for example — Giovane Machado, Sep 11 '18 at 01:17
I was thinking that the RecyclerViews is a widget, like the Button, and I can use it in my Screen — Giovane Machado, Sep 11 '18 at 01:19
Exactly is a widget, then show us what you have tried, in SO you should show what you have tried, and point out that part does not work, then the community will try to point out where the error is and how it should be corrected, so you learn more. try even if it is not correct?. great that you've shown it that way we won all — eyllanesc, Sep 11 '18 at 01:25
what is `ListaEventos`?I see that you use it but I do not see where you have declared it — eyllanesc, Sep 11 '18 at 01:27
Thank you and sorry for this mistake. I think it was the tiredness :) — Giovane Machado, Sep 11 '18 at 01:28
ListaEvento is my try of use RecycleView, like the example of docs — Giovane Machado, Sep 11 '18 at 01:30

score 3 · Accepted Answer · answered Sep 11 '18 at 01:40

You should not inherit from 2 widgets but what widget is going to be painted? For example, if you want an image that behaves like a button, you must inherit from the Image widget and the ButtonBehavior class, that is, visually it is an image but added the button behavior.

So to solve your problem it is not correct to use the inheritance but the composition, that is, to add the RecyclerView as a son of the Screen.

*.py

import kivy
from kivy.app import App, Builder
from kivy.config import Config
from kivy.uix.screenmanager import ScreenManager, Screen

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


kivy.require('1.10.1')
Builder.load_file('ing.kv')
Config.read('config.ini')

sm = ScreenManager()
sm.add_widget(ListaEventos(name='listaEventos'))


class IngApp(App):
    def build(self):
        return sm


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

ing.kv

<ListaEventos>:
    rv: rv # expose the widget

    canvas:
        Rectangle:
            source: 'design/fundo.png'
            size: self.width, self.height

    RecycleView:
        id: rv
        viewclass: 'Label'
        RecycleBoxLayout:
            default_size: None, dp(56)
            default_size_hint: 1, None
            size_hint_y: None
            height: self.minimum_height
            orientation: 'vertical'

Thank you so much!! You help me a lot. Sorry for the mistakes, and thank you again for the attention. This do exactly what I want, now I'll get to do other things. :D — Giovane Machado, Sep 11 '18 at 03:48

How can I use the RecycleView of Kivy on kv language with ScreenManager?

1 Answers1