Hi I have a question about passing variables in Kivy. So what my app is trying to do is:

Have a TextInput field that for a name of an item. However, I have a button where when I click, I can scan the QR, QR is translated into a text and the TextInput field is filled with updated with the QR translation.

I also Screen Manager and Sockets.

How can I achieve this?

The main problem I am struggling is when the QR is translated, it is saved as self.codename in the QrScreen. Since I want to update the TextField in the MainScreen, the MainScreen needs to update the self.codename from "" to the translated QR. This is the process that I don't understand.

here is the code:

import kivy
from kivy.app import App

from kivy.uix.label import Label
from kivy.uix.gridlayout import GridLayout
from kivy.uix.textinput import TextInput
from kivy.uix.button import Button
from kivy.uix.widget import Widget
from kivy.properties import ObjectProperty
from kivy.uix.screenmanager import ScreenManager, Screen


# Import Package that deals with socket
import socket_client

# Import QR Reader
import qr_reader

# from android.permissions import request_permissions, Permission
# request_permissions([
#     Permission.CAMERA,
#     Permission.WRITE_EXTERNAL_STORAGE,
#     Permission.READ_EXTERNAL_STORAGE
# ])



class MainScreen(Screen):
    def update_name(self, new_qr):
        print(' Iam updating this name '   new_qr)

    def turn_camera_on(self):
        print("turning camera on...")

    
    def send_message(self, _):
        message = _
        print(message)

        if message:
            socket_client.send(message)


class QrScreen(Screen):
    camera = ObjectProperty(None)
   
    def capture_image(self):

        texture = self.camera.texture
        size = texture.size
        pixels = texture.pixels
        self.codename = qr_reader.convert_qr(size, pixels)
        print(self.codename)
        # update the text in the main page

        # switch screen to main page


    def send_message(self, _):
        message = _
        print(message)

        if message:
            socket_client.send(message)

class SettingsScreen(Screen):
    ipadd = ObjectProperty(None)
    port = ObjectProperty(None)
    username = ObjectProperty(None)
    def connect(self):
        print(f"joining {self.ipadd.text} | {self.port.text} AS {self.username.text}")


        # Get information for sockets client
        port = int(self.port.text)
        ip = self.ipadd.text
        username = self.username.text

        if not socket_client.connect(ip, port, username, show_error):
            return


class MyApp(App):

    # Initiate the variable for codename

    codename = ObjectProperty(None)
    def build(self):
        self.codename = ""
        
        # Create the screen manager
        sm = ScreenManager()
        sm.add_widget(MainScreen(name='mainpage'))
        sm.add_widget(QrScreen(name='qrpage'))
        sm.add_widget(SettingsScreen(name='settings'))

        return sm


def show_error(message):
    pass


if __name__ == '__main__':
    theapp = MyApp()
    theapp.run()

my.kv:

<MainScreen>:
    GridLayout:
        cols: 1

        GridLayout:
            cols: 2
            codename: codename
            Label:  
                text: "Code Name"
            TextInput:
                id: codename
                multiline: False
            Button:
                text: 'Scan QR'
                on_press: root.manager.current = 'qrpage'
                on_press: root.turn_camera_on()
            Button:
                text: 'Go'
                on_press: root.send_message("Go")
            Button:
                text: 'Stop'
                on_press: root.send_message("Stop")
            Button:
                text: 'Setting'
                on_press: root.manager.current = 'settings'

<QrScreen>:
    camera: camera
    GridLayout:

        cols: 1
        Camera:
            id: camera
            resolution: (640,480)
            play: False
        GridLayout:
            cols: 2
            ToggleButton:
                text: 'Play'
                on_press: camera.play = not camera.play

            Button:
                text: 'Capture'
                on_press: root.capture_image()

            Button:
                text: 'Back'
                on_press: root.manager.current = 'mainpage'


<SettingsScreen>:
    ipadd: ipadd
    port: port
    username: username

    GridLayout:
        cols: 1
        GridLayout:
            cols:2

            Label:
                text: "IP Address: "
            TextInput:
                id: ipadd
                text: "192.168.1.65"
                multiline: False

            Label:
                text: "Port: "
            TextInput:
                id: port
                text: "1234"
                multiline: False

            Label:
                text: "Username: "
            TextInput:
                id: username
                text: "User"
                multiline: False

            Button:
                text: 'Join'
                on_press: root.connect()
            
            Button:
                text: 'Back'
                on_press: root.manager.current = 'mainpage'

            

CodePudding user response：

Haven't tested this code, but using ids and the get_screen() method of ScreenManager should allow you to update the Textinput:

def capture_image(self):

    texture = self.camera.texture
    size = texture.size
    pixels = texture.pixels
    self.codename = qr_reader.convert_qr(size, pixels)
    print(self.codename)

    # update the text in the main page
    main_screen = self.manager.get_screen('mainpage')
    main_screen.ids.codename.text = self.codename

    # switch screen to main page
    self.manager.current = `mainpage`