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PySide6 QQmlApplicationEngine failed to load component

Hello I designed an my UI using Qt Design Studio (Community Edition) and exported it to a qrc file then compiled to Python using pyside6-rcc then loaded the main.qml file inside main.py using "qrc:/main.qml" resource link but I have these errors Type App not available.
This is my file structure;
- qml
- contents
* App.qml
* ... // Other Files
+ imports
* main.qml
* uifiles.qrc
* uifiles.py // Generated by [pyside6-rcc uifiles.qrc -o uifiles.py]
* main.py
Content of qml/content/App.qml;
import QtQuick
import QtQuick.Window
import "qrc:/content"
import QtQuick.VirtualKeyboard
Window {
width: mainScreen.width
height: mainScreen.height
visible: true
title: "IntelUI"
Screen01 {
id: mainScreen
}
InputPanel {
id: inputPanel
property bool showKeyboard : active
y: showKeyboard ? parent.height - height : parent.height
Behavior on y {
NumberAnimation {
duration: 200
easing.type: Easing.InOutQuad
}
}
anchors.leftMargin: Constants.width/10
anchors.rightMargin: Constants.width/10
anchors.left: parent.left
anchors.right: parent.right
}
}
Content of qml/main.qml;
import QtQuick
import "qrc:/content"
App {
}
Content of main.py;
import sys
import qml.uifiles
from PySide6.QtCore import QUrl
from PySide6.QtGui import QGuiApplication
from PySide6.QtQml import QQmlApplicationEngine
if __name__ == "__main__":
app = QGuiApplication(sys.argv)
engine = QQmlApplicationEngine()
engine.load(QUrl("qrc:/main.qml"))
if not engine.rootObjects():
sys.exit(-1)
sys.exit(app.exec())
Errors generated by python main.py;
QQmlApplicationEngine failed to load component
qrc:/main.qml:7:1: Type App unavailable
qrc:/content/App.qml:42:5: Type Screen01 unavailable
qrc:/content/Screen01.ui.qml:41:13: Type MainStream unavailable
qrc:/content/MainStream.ui.qml:12:1: module "QtQuick.Studio.Components" is not installed
Note: I have the following installed PySide6, PySide6-Addons
Any help will useful. Thank You!

Testing QML based app with pytest in python

I would like to test my QML frontend code along with my Python backend code(using PySide2) with Pytest preferably, and be able to send keyClicks, MouseClicks and signals just like pytest-qt plugin does. I have already checked out pytest-qml, but the test code is written via QML, and then only ran via via pytest, but I would like to send events and such from python itself, not QML
Basically, having the python code as such:
"""
Slots, Signals, context class etc etc...
"""
app = QGuiApplication([])
engine = QQmlApplicationEngine()
engine.load(QUrl.fromLocalFile("main.qml"))
app.exec_()
and a simple main.qml file, as such,
import QtQuick 2.15
import QtQuick.Layouts 1.15
import QtQuick.Window 2.2
import QtQuick.Controls 2.15
ApplicationWindow {
id: mywin
width: Screen.desktopAvailableWidth
height: Screen.desktopAvailableHeight
visible: true
FileDialog {
id: openDialog
title: "mydialog"
onAccepted: {
}
}
Button {
objectName: "mybtn"
width: 200
height: 200
id: btn
text: "hello"
onClicked: {
openDialog.open()
}
}
}
I would like to do (pseudo-code)something like
def test_file_open():
#Grab QQuickItem(btn)
#Send mouse event to click btn
#Send string to file dialog
# assert string sent == string selected
The pytest-qt plugin would work, but functions take QWidget and QML deals with QQuickItems, which as far as I know doesnt deal with QWidgets.
Is it even possible, or my only option to test my app slots etc is via the pytest-qml ? Perhaps its the easiest way, but perhaps there are other options :)
Edit:
If you use import Qt.labs.platform 1.1 instead of the import QtQuick.Dialogs 1.3, and force QML to not use native dialog, then just change
# assert myfiledialog.property("fileUrl").toLocalFile() == filename # uses QDialog
assert myfiledialog.property("currentFile").toLocalFile() == filename # using QLabs Dialog
And then using the rest of the code from accepted answer it will work, so apparently its very important that it does not use a native dialog.
If anyone else in the future knows how to make it work with native dialog and using QtQuick.Dialogs 1.3 as the original question presented, it would be nice :). But this is still nice to test overall!

You can use the same API since pytest-qt is based on QtTest. Obviously you must understand the structure of the application, for example that the FileDialog is just a QObject that only manages a QWindow that has the dialog, in addition to managing the positions of the items with respect to the windows.
import os
from pathlib import Path
from PySide2.QtCore import QUrl
from PySide2.QtQml import QQmlApplicationEngine
CURRENT_DIR = Path(__file__).resolve().parent
def build_engine():
engine = QQmlApplicationEngine()
filename = os.fspath(CURRENT_DIR / "main.qml")
url = QUrl.fromLocalFile(filename)
engine.load(url)
return engine
def main():
app = QGuiApplication([])
engine = build_engine()
app.exec_()
if __name__ == "__main__":
main()
import QtQuick 2.15
import QtQuick.Controls 2.15
import QtQuick.Dialogs 1.3
import QtQuick.Layouts 1.15
import QtQuick.Window 2.2
ApplicationWindow {
id: mywin
width: Screen.desktopAvailableWidth
height: Screen.desktopAvailableHeight
visible: true
FileDialog {
id: openDialog
objectName: "myfiledialog"
title: "mydialog"
onAccepted: {
}
}
Button {
id: btn
objectName: "mybtn"
width: 200
height: 200
text: "hello"
onClicked: {
openDialog.open();
}
}
}
import os
from PySide2.QtCore import QCoreApplication, QObject, Qt, QPointF
from PySide2.QtGui import QGuiApplication
from PySide2.QtQuick import QQuickItem
from PySide2.QtWidgets import QApplication
import pytest
from app import build_engine
#pytest.fixture(scope="session")
def qapp():
QCoreApplication.setOrganizationName("qapp")
QCoreApplication.setOrganizationDomain("qapp.com")
QCoreApplication.setAttribute(Qt.AA_DontUseNativeDialogs)
yield QApplication([])
def test_app(tmp_path, qtbot):
engine = build_engine()
assert QCoreApplication.testAttribute(Qt.AA_DontUseNativeDialogs)
with qtbot.wait_signal(engine.objectCreated, raising=False):
assert len(engine.rootObjects()) == 1
root_object = engine.rootObjects()[0]
root_item = root_object.contentItem()
mybtn = root_object.findChild(QQuickItem, "mybtn")
assert mybtn is not None
center = QPointF(mybtn.width(), mybtn.height()) / 2
qtbot.mouseClick(
mybtn.window(),
Qt.LeftButton,
pos=root_item.mapFromItem(mybtn, center).toPoint(),
)
qtbot.wait(1000)
qfiledialog = None
for window in QGuiApplication.topLevelWindows():
if window is not root_object:
qfiledialog = window
assert qfiledialog is not None, QGuiApplication.topLevelWindows()
file = tmp_path / "foo.txt"
file.touch()
filename = os.fspath(file)
for letter in filename:
qtbot.keyClick(qfiledialog, letter, delay=100)
qtbot.wait(1000)
qtbot.keyClick(qfiledialog, Qt.Key_Return)
qtbot.wait(1000)
myfiledialog = root_object.findChild(QObject, "myfiledialog")
assert myfiledialog is not None
assert myfiledialog.property("fileUrl").toLocalFile() == filename
Note: The test may fail if the filedialog uses the native window, you could use tools like pyinput but a simpler option is to use virtualenv.

Updates can only be scheduled from GUI thread or from QQuickItem::updatePaintNode()

I'm trying to change Image with Pushbutton (GPIO PINs) stored inside a folder using QML with PyQt5
Python Code:
from gpiozero import Button
from signal import pause
from PyQt5.QtCore import *
from PyQt5.QtGui import *
from PyQt5.QtQml import *
import os, time, sys
def btn_pressed():
global r
return lambda: r.setProperty("source", "/home/pi/Desktop/example/sample/img/img1.jpg")
button1 = Button(20)
myApp = QGuiApplication([])
myEngine = QQmlApplicationEngine()
directory = os.path.dirname(os.path.abspath(__file__))
myEngine.load(QUrl.fromLocalFile(os.path.join(directory, 'simple1.qml')))
if not myEngine.rootObjects():
print("root object not found")
r = myEngine.rootObjects()[0].findChild(QObject, "DisplayImage")
dir(r)
print("Main Thead id ",myApp.thread())
updateUI = UpdateUI()
button1.when_pressed = btn_pressed()
myEngine.quit.connect(myApp.quit)
sys.exit(myApp.exec_())
QML:
import QtQuick 2.10
import QtQuick.Controls 1.6
import QtQuick.Window 2.2
ApplicationWindow {
id : main
title: qsTr("Test")
width: 640
height: 480
visible: true
Rectangle{
width: parent.width
height: parent.height
Image {
id: img
source: ""
width : main.width;
fillMode : Image.PreserveAspectFit
objectName: "DisplayImage"
}
}
}
When I Pressed the Push Button Connected to GPIO 20 in raspberry Pi 4 , I'm Getting below error message.
QObject: Cannot create children for a parent that is in a different thread.
(Parent is QQmlApplicationEngine(0x10f5ba0), parent's thread is QThread(0xf6f7c0), current thread is QThread(0xa98007c8)
Updates can only be scheduled from GUI thread or from QQuickItem::updatePaintNode()
I also tried creating class with a method changing Image Source Property and then calling the same method(via Class Object) upon PushButton press but it shows same error message
Is there a way to set Image's Source Property in QML - from parent thread in Python.
In Winforms we can Avoid "Cross-Thread Violation Error" by using Delegates.
Can we Use Signal and Slot to Solve this Problem in PyQt5.

gpiozero uses threads to be able to monitor the gpio so as not to block the main GUI, so the associated function when_pressed will be executed in that thread but Qt prohibits updating GUI elements such as the image from another thread.
The solution is to create a QObject that emits the signal in the method associated with when_pressed since the signals are thread-safe.
On the other hand it is not good to modify the QML elements from C++/Python, it is better to export the QObject to QML and make the connections in that scope.
import os
import sys
from gpiozero import Button
from PyQt5.QtCore import pyqtSignal, QObject, QUrl
from PyQt5.QtGui import QGuiApplication
from PyQt5.QtQml import QQmlApplicationEngine
class ButtonManager(QObject):
pressed = pyqtSignal()
def __init__(self, parent=None):
super().__init__(parent)
self._button = Button(20)
self._button.when_pressed = self._on_when_pressed
def _on_when_pressed(self):
self.pressed.emit()
if __name__ == "__main__":
app = QGuiApplication(sys.argv)
button_manager = ButtonManager()
engine = QQmlApplicationEngine()
engine.rootContext().setContextProperty("button_manager", button_manager)
current_dir = os.path.dirname(os.path.abspath(__file__))
engine.load(QUrl.fromLocalFile(os.path.join(current_dir, "simple1.qml")))
if not engine.rootObjects():
print("root object not found")
sys.exit(-1)
engine.quit.connect(app.quit)
sys.exit(app.exec_())
simple1.qml
import QtQuick 2.10
import QtQuick.Controls 1.6
import QtQuick.Window 2.2
ApplicationWindow {
id : main
title: qsTr("Test")
width: 640
height: 480
visible: true
Rectangle{
anchors.fill: parent
Image {
id: img
width : main.width
fillMode : Image.PreserveAspectFit
}
}
Connections{
target: button_manager
onPressed: img.source = "/home/pi/Desktop/example/sample/img/img1.jpg"
}
}

Using QtCharts in Qt Creator with python

I am using Qt Creator to create a QtQuick program using Python. I want to add the QtCharts module to my QML files, but I get the error message
QML module not found (QtCharts)
In a QtQuick project using C++, one would include QtCharts by adding QT += charts in the .pro file.
Is there a similar command to add in the main.pyproj file?
Note that the program runs correctly when built through the python script, but I want to access the features used by the designer in Qt Creator.
The main.pyproject is as follows:
{"files": ["main.py","frontend/main.qml"]}
The main.py file:
import os
import sys
import PyQt5.QtQml
import PyQt5.QtCore
import PyQt5.QtWidgets
if __name__ == '__main__':
os.environ['QT_QUICK_CONTROLS_STYLE'] = 'Default'
app = PyQt5.QtWidgets.QApplication(sys.argv)
engine = PyQt5.QtQml.QQmlApplicationEngine()
engine.load('frontend/main.qml')
if not engine.rootObjects():
sys.exit(-1)
sys.exit(app.exec_())
the frontend/main.qml file:
import QtQuick 2.12
import QtQuick.Controls 2.13
import QtQuick.Layouts 1.12
import QtCharts 2.10
ApplicationWindow {
id: window
visible: true
title: 'Neuron Network Sandbox'
ChartView {
width: 400
height: 300
antialiasing: true
PieSeries {
id: pieSeries
PieSlice { label: "eaten"; value: 94.9 }
PieSlice { label: "not yet eaten"; value: 5.1 }
}
}
}

How to bind buttons in Qt Quick to Python PyQt 5

How can bind the buttons I create in a .qml script to python PyQt5 code?
example:
python:
import sys
from PyQt5.QtCore import QObject, QUrl, Qt
from PyQt5.QtWidgets import QApplication
from PyQt5.QtQml import QQmlApplicationEngine
if __name__ == "__main__":
app = QApplication(sys.argv)
engine = QQmlApplicationEngine()
ctx = engine.rootContext()
ctx.setContextProperty("main", engine)
engine.load('test.qml')
win = engine.rootObjects()[0]
win.show()
sys.exit(app.exec_())
qml:
import QtQuick 2.2
import QtQuick.Window 2.1
import QtQuick.Controls 1.2
import QtQuick.Dialogs 1.1
ApplicationWindow {
title: qsTr("Test Invoke")
width: 200
height: 100
Button{
y : 70
text : "About"
onClicked: {
print('Hello')
}
}
}
How can I do something with Python when the button is clicked?
Also: Does anyone has a good resource of examples or doc. about pyqt + qml (qt quick)?

If you name the button, you can connect to its onClick signal, or to a custom signal that it emits in onClicked. Example:
ApplicationWindow {
title: qsTr("Test Invoke")
width: 200
height: 100
Button {
signal messageRequired
objectName: "myButton"
y : 70
text : "About"
onClicked: messageRequired()
}
}
Note the signal in Button and the objectName property. Then the Python code just before exec could be for example:
def myFunction():
print 'handler called'
button = win.findChild(QObject, "myButton")
button.messageRequired.connect(myFunction)
button.clicked.connect(myFunction) # works too
Note that in the Button above, onClicked just emits the messageRequired signal, so it is better to drop the custom signal and connect to clicked directly. Both onClicked() and any slots connected to clicked will get called when you click button.

There is another solution which uses a Python model (QObject) in QML.
Python
engine = QQmlApplicationEngine()
engine.load("main.qml")
class Greeter(QObject):
#pyqtSlot(str)
def sayHello(self, name):
print("Hello, " + name)
ctx = engine.rootContext()
ctx.setContextProperty("greeter", Greeter())
QML
Button {
onClicked: {
greeter.sayHello("Alice")
}
}
Ref.
https://wiki.qt.io/Qt_for_Python/Connecting_QML_Signals