Using QNetworkAccessManager freezes the QML GUI

James A

I created simple QML Application with a single button. I clicking the button the button clicked message is printed on application output. But When I declare the QNetworkAccessManager class it completely freezes the GUI. The button does not respond to the button click events. Where as when I comment the networkmanger the GUI works fine.

Added the code below

#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QtNetwork>

int main(int argc, char *argv[])
{
#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
#endif

    QGuiApplication app(argc, argv);

// Commenting this line removes GUI freeze
    QNetworkAccessManager manager;

    QQmlApplicationEngine engine;
    const QUrl url(QStringLiteral("qrc:/main.qml"));
    QObject::connect(&engine, &QQmlApplicationEngine::objectCreated,
                     &app, [url](QObject *obj, const QUrl &objUrl) {
        if (!obj && url == objUrl)
            QCoreApplication::exit(-1);
    }, Qt::QueuedConnection);
    engine.load(url);

    qDebug() << "Application ended ";

    return app.exec();
}

import QtQuick 2.6
import QtQuick.Window 2.2
import QtQuick.Controls 2.2

Window {
    width: 640
    height: 480
    visible: true
    title: qsTr("Hello World")

    Button {
        id: button
        x: 270
        y: 195
        text: qsTr("Button")
        onClicked: {
            console.log("Button clicked")
        }
    }
}

Note :
I am testing this on iMX6ULL processor which has display connected to it. And using Qt version 5.11.3

sierdzio

Judging from code alone - this should work fine. You can check on a desktop if you are able to replicate such behaviour. I suspect it to be a quirk of your embedded board or a bug in Qt (update to newer version if possible!).

You can move QNAM to a separate thread, then it should not interfere.

James A

Hi @sierdzio ,

In desktop it is working fine. Moving it to different thread fixed the GUI freeze issue in the device. I will continue to find out , if it is a bug in device or in Qt version.
Thanks for the reply

Regards,
James A