kivy - I want to change an attribute of a widget in a screen out of a popup

问题

I want to change the color of an image. This image is placed on an button on a screen with screenmanager. When I push the button a popup appears to choose a color. This color should now be saved in a global variable and set as color for the (former white) image. My problem is, i cant access the property of the image from the class of the popup.

The relevant part of the .kv:

<HomeScreen>:

sm: sm
name: 'ScreenManager'

BoxLayout:
    orientation: 'vertical'
    rows: 2

    ActionBar:
        [...]

    ScreenManager:
        id: sm
        size_hint_y: .935

        Screen1:
            name: "screen_1"
        Screen2:
            name: "screen_2"
        Screen3:
            name: "screen_3"
[...]

<Popup_F>:

size_hint: .75, .5
auto_dismiss: True
BoxLayout
    orientation: 'horizontal'
    padding: 10, 0

    BoxLayout
        orientation: 'vertical'

        Slider:
            id: on_value_slider_r
            on_value:
                root.on_value_slider_rgb()

        Slider:
            id: on_value_slider_g
            on_value:
                root.on_value_slider_rgb()

        Slider:
            id: on_value_slider_b
            on_value:
                root.on_value_slider_rgb()

And the .py:

class Screen1(Screen):
[...]

def colorchanger(self):

    farbenw = Popup_F()
    farbenw.open()

def colorchangern(self):
    # next line should change the color (as work around) of the Image but has no effect:
    self.ids.image_color_change.color = (r_R1, g_R1, b_R1, 1)


class Farbe(Popup):

def on_value_slider_rgb(self):
    global r_R1
    global g_R1
    global b_R1
    r_R1 = self.ids.on_value_slider_r.value
    g_R1 = self.ids.on_value_slider_g.value 
    b_R1 = self.ids.on_value_slider_b.value 

    # next line does cause an error
    self.ids.image_color_change.color = (r_R1, g_R1, b_R1, 1)
    Screen1().colorchangern()

The error I get:

AttributeError: 'super' object has no attribute '__ getattr __'

it only appers with the marked line... I dont know how I can realize this without errors! I hope I´ve done everything correct with my first question!

Thank you!

回答1:

You could for example pass the object you want to access to the popup.
Try this example. This will set the buttons text to the sliders value:

from kivy.app import App
from kivy.lang import Builder
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.properties import StringProperty
from kivy.uix.popup import Popup


Builder.load_string(

'''

<Screen1>:
    BoxLayout:
        Button:
            text: root.button_text
            on_release:
                root.popup.open()

<MyPopup>:
    BoxLayout:
        orientation: "vertical"
        Slider:
            on_value:
                root.screen.button_text = str(self.value)
        Button:
            text: "Okey!"
            on_release:
                root.dismiss()

<MySm>:
    Screen1:


'''

)


class MySm(ScreenManager):
    pass


class MyPopup(Popup):

    def __init__(self,screen,**kwargs):
        super(MyPopup,self).__init__(**kwargs)
        self.screen = screen


class Screen1(Screen):
    button_text = StringProperty("text")
    def __init__(self,**kwargs):
        super(Screen1,self).__init__(**kwargs)
        self.popup = MyPopup(self)


class MyApp(App):

    def build(self):
        return MySm()


MyApp().run()

来源：https://stackoverflow.com/questions/42373746/kivy-i-want-to-change-an-attribute-of-a-widget-in-a-screen-out-of-a-popup