(Python) Cannot call findChild(QObject, 'child') on QObject. Returns None.

[0BobTheJanitor]

Sorry if this is not the appropriate section, I noticed there is a bindings section, but not many people seem to visit over there. Basically, I really love QT from what I've used so far, but with Python I've run into issues, mainly with connecting to signals, and finding children with the function findChild.

Unfortunitely, I don't have much time, so I would like to know whether this is an issue with PyQt, or if there is a solution/workaround I can use for the time being. If I have to, I'll go backroll into Qt4 for what I'd like to do.

Also ignore the ugly qml file, I've been too stuck on this issue to make it look pretty.

I also have problems of crashes of the window emulation when using the connections tab of the designer in QT Creator, but I'll post a separate thread about that.

import sys

from PyQt5.QtCore import QUrl, QSize, QObject
from PyQt5.QtGui import QGuiApplication
from PyQt5.QtQuick import QQuickView


LOGIN_SCREEN_SIZE = QSize(640, 350)


def main():
    application = QGuiApplication(sys.argv)

    login_window = QQuickView()
    login_window.setSource(QUrl('loginscreen.qml'))

    login_window.setMinimumSize(LOGIN_SCREEN_SIZE)
    login_window.setMaximumSize(LOGIN_SCREEN_SIZE)

    login_window.show()

    ## vvvv Returns None ## I've also experimented in how this is implemented, but I can't get it to work any way I try
    print(login_window.findChild(QObject, 'white_background'))
    
    ## vvvv Doesn't connect ##
    login_window.rootObject().open_main_app.connect(app)

    sys.exit(application.exec_())


def app(username, password):
    print("YAY")

    main_window = QQuickView()
    main_window.show()


if __name__ == '__main__':
    main()

import QtQuick 2.4
import QtQuick.Controls 1.5

Item {
    id: window
    objectName: window
    x: 0
    height: 350
    visible: true
    transformOrigin: Item.Center
    rotation: 0

    signal open_main_app(string username, string password)

    Rectangle {
        id: white_background
        objectName: white_background
        x: 0
        y: 0
        width: 640
        height: 350
        color: "#ffffff"
        border.width: 0

print(login_window.findChild(QObject, 'white_background'))
        Rectangle {
            id: green_background
            x: 0
            y: 0
            width: 640
            height: 138
            color: "#30945d"
        }
//your code here
        Text {
            id: login_text
            x: 0
            y: 0
            width: 640
            height: 124
            color: "#b3d756"
            text: qsTr("LOGIN")
            styleColor: "#f60000"
            style: Text.Normal
            font.bold: true
            verticalAlignment: Text.AlignVCenter
            horizontalAlignment: Text.AlignHCenter
            font.pixelSize: 112
        }


        TextField {
            id: username_box
            x: 149
            y: 160
            width: 384
            height: 30
            placeholderText: qsTr("Steve")
        }


        TextField {
            id: password_box
            x: 149
            y: 215
            width: 384
            height: 30
            echoMode: 2
            placeholderText: qsTr("qwerty123")
        }


        Label {
            id: label1
            x: 40
            y: 166
            text: qsTr("Username")
        }


        Label {
            id: label2
            x: 40
            y: 221
            text: qsTr("Password")
        }


        Button {
            id: login_button
            x: 548
            y: 308
            text: qsTr("Go")

            onClicked:
            {
                window.open_main_window(username_box.text, password_box.text)

                //Qt.quit() << Only works when launching from C++ file
            }
        }

    }

}

So the problem is this returns None, despite there being an object of that name.

print(login_window.findChild(QObject, 'white_background'))

And this, when the button is pressed, not calling the connected function.

login_window.rootObject().open_main_app.connect(app)

Again, I'm sorry if this is the wrong section to have posted this, I just would like some help, as I really do love the flexibility this toolkit has to offer, and as my Stack Overflow thread went silently undread.