Cannot Use ApplicationWindow (QML) On PySide2

I'm trying to run a simple Qt application using QML and more specifically ApplicationWindow. My Python code is a simple QML caller: import sys from PySide2.QtWidgets import QApplic

Solution 1:

First, as pyside returns:

QQuickView does not support using windows as a root item. If you wish to create your root window from QML, consider using QQmlApplicationEngine instead.

This is a working example:

main.py

import sys
from PySide2.QtWidgets import QApplication
from PySide2.QtCore import Qt, QCoreApplication
from PySide2.QtQml import QQmlApplicationEngine

if __name__ == '__main__':

    app = QApplication(sys.argv)

    QApplication.setAttribute(Qt.AA_EnableHighDpiScaling)
    QCoreApplication.setAttribute(Qt.AA_UseHighDpiPixmaps)

    engine = QQmlApplicationEngine('view.qml')

    sys.exit(app.exec_())

view.qml

import QtQuick.Controls 2.4
import QtQuick 2.0

ApplicationWindow {

    title: "Qt Quick Controls Gallery"
    visible: true
    width: 640
    height: 480
    Rectangle {
        width: 30
        height: 30
        color: "blue"
    }
}

Solution 2:

If you read the docs:

The QQuickView class provides a window for displaying a Qt Quick user interface.

That is, QQuickView provides a window to show Items, but ApplicationWindow is already a window so you do not need and should not use QQuickView anymore, in the case of ApplicationWindow you must use QQmlApplicationEngine:

main.py

import sys
from PySide2 import QtCore, QtGui, QtQml

if __name__ == '__main__':

    QtCore.QCoreApplication.setAttribute(QtCore.Qt.AA_EnableHighDpiScaling)
    app = QtGui.QGuiApplication(sys.argv)

    engine = QtQml.QQmlApplicationEngine()

    url = QtCore.QUrl.fromLocalFile('view.qml')
    engine.load(url)
    if not engine.rootObjects():
        sys.exit(-1)

    sys.exit(app.exec_())

view.qml

import QtQuick 2.7
import QtQuick.Controls 2.4

ApplicationWindow {
    title: "Qt Quick Controls Gallery"
    width: 640
    height: 480
    visible: true // <---
}