Pass argument to other Property

Question

I have two screens. On Box I have a button with a name. When I click the button, I want to switch the screen to ChangeText see the name there. Once I click the button the text of Box.name should be the TextInput-text. I can't find a solution.

kv-file

<ChangeText>:
    BoxLayout:
        TextInput:
            id: txt
            multiline: False
            text: Box.name
        Button:
            text: "Save"
            on_release: Box.name = txt.text

<Box>:
    BoxLayout:
        Button:
            text: root.name
            on_press: root.change_text(root.name)

py-file

class ChangeText(Screen):
    pass

class Box(Screen):
    name = StringProperty("sometext")

    def change_text(label):
        sm.current = 'changetext'
        ### ?!?!? ###

score 0 · Answer 1 · answered Sep 09 '18 at 18:32

So I found a workaround, what might be instable but works for now. Took me hours.

I just declared eveyr property as global variable. Then I wrote a global export functio, that overwrite all global variables. So whenever I switch the screen, I execute export(props). Now all properties from my last view are exported. I need to update all properties of each screen. Therefore each screen has update(). Export() is extended by a for loop over all screens, calling the update().

home_name = ''

def export(hn):
    home_name = hn
    for screen in sm.screens:
        screen.update()

class Team(BoxLayout):
    home_name = StringProperty()

    def update(self):
        global home_name
        self.home_name = home_name 


class Box(BoxLayout):
    home_name = StringProperty("Home")

    def load_team(self):
        export(self.home_name)
        sm.current = 'team'

    def update(self):
        global home_name
        self.home_name = home_name 
        #further screen specific actions

kv

<Team>:
    id: team
    TextInput:
        id: team_name
        text: root.home_name
        multiline: False
    Button:
        text: "Save"
        on_press: root.save(team_name.text)

<Box>:
     Button:
         id: btn_home_name
         text: root.home_name
         on_press: root.load_team()

I hope there is an easier approach. – Franz Schwerdtmann Sep 09 '18 at 18:33 — Franz Schwerdtmann, Sep 09 '18 at 18:33

score 0 · Accepted Answer · answered Sep 09 '18 at 21:12

Problem - attribute, name

When using Kivy ScreenManager, do not declare a variable/attribute called, name because it is a reserved word used for naming/identifying a screen.

ScreenManager » name

name
Name of the screen which must be unique within a ScreenManager. This is the name used for ScreenManager.current.

name is a StringProperty and defaults to ‘’.

Solution

The solution is as follow:

Rename the class level property, name to home_name or anything except name
Add id to each screen.
Use root.manager.ids to reference widgets in declared in another screen.
Replace sm.current with self.manager.current because each screen has by default a property manager that gives you the instance of the ScreenManager used.

Example

main.py

from kivy.app import App
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.properties import StringProperty


class ScreenManagement(ScreenManager):
    pass


class ChangeText(Screen):
    pass


class Box(Screen):
    home_name = StringProperty("sometext")

    def change_text(self):
        self.manager.current = 'changetext'


class TestApp(App):

    def build(self):
        return ScreenManagement()


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

test.kv

#:kivy 1.11.0

<ScreenManagement>:
    Box:
        id: box
        name: 'box'

    ChangeText:
        id: changeText
        name: 'changetext'

<ChangeText>:
    BoxLayout:
        TextInput:
            id: txt
            multiline: False
            text: root.manager.ids.box.home_name
        Button:
            text: "Save"
            on_release: root.manager.ids.box.home_name = txt.text

<Box>:
    BoxLayout:
        Button:
            text: root.home_name
            on_press: root.change_text()