How do you send data from a QtWidget application Mainwindow.cpp file to a update the value of a progressbar in QML?

[Kokoy]

I'm new to Qt and still figuring my way around. I've started off with a course covering the basics. I am currebtly tasked to understand as much as I can in QML to see if possible to integrate it into our software which is a standard Qt Widget Application.

I basically made a dummy app for practice, and I used a QtQuickWidget inside of a UI form of a Qt Widget application. Within it I have a progressbar. I want to update the progress of the progressbar with a value sent from the Mainwindow.cpp file, which has a function there that used the QTimer class to run for a certain period of time and with every second the progress increases until reaching a 100%.

mainwindow.cpp:

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    QQmlContext *context = ui->quickWidget->rootContext();

    QString title = "Progress Bar App";
    int progress = 0;
    context->setContextProperty("_myString",title); //Set Text in QML that says Hello World
    progress = myFunction();
    context->setContextProperty("_myProgress", progress);

    timer = new QTimer(this);

    connect(timer, SIGNAL(timeout()), this, SLOT(myFunction()));
    timer->start(1000);



    ui->quickWidget->setSource(QUrl("qrc:/main.qml"));
    ui->quickWidget->show();
}

MainWindow::~MainWindow()
{
    delete ui;
}

int MainWindow::myFunction(){
    //Calculate progress
    static uint16_t total_time = 50000;
    static uint16_t progress = 0;
    static uint16_t i = 0;

    if(i < total_time){
        i = i + 1000;
                progress = ((i)*100)/total_time;
                qDebug()<<"Progress: "<<progress<<endl;
    }else{
        timer->stop();
        qDebug()<<"Finished..."<<endl;
    }
   

    return progress;

}

QML file:

Rectangle{
    id:mainRect;
    color: "black";

            gradient: Gradient {
                   GradientStop { position: 0.0; color: "black" }
                   GradientStop { position: 0.33; color: "white" }
                   GradientStop { position: 1.0; color: "black" }
               }


    Text {
        id: rectText
        text: ""+_myString
        color: "green"
        font.pointSize: 40
        anchors.horizontalCenter: parent.horizontalCenter
    }

    ProgressBar{
        id:progressbar
        from: 0; to:100;
        anchors.centerIn: parent
        height: 50

        ColorAnimation {
            from: "orange"
            to: "green"
            duration: 200
        }
        
        onValueChanged: _myProgress
    }



    Button{
        id: control
            text: qsTr("Button")
            anchors.right: progressbar.right
            anchors.left: progressbar.left
            anchors.top : progressbar.bottom
            font.bold: true
            font.pixelSize: 20

            MouseArea{
                anchors.fill: control
            }

            contentItem: Text {
                text: control.text
                font: control.font
                opacity: enabled ? 1.0 : 0.3
                color: "white"
                horizontalAlignment: Text.AlignHCenter
                verticalAlignment: Text.AlignVCenter
                elide: Text.ElideRight
            }

            background: Rectangle {
                implicitWidth: 100
                implicitHeight: 40
                color: parent.down ? "darkgreen" : (parent.hovered ? "lightgreen" : "green")
                opacity: enabled ? 1 : 0.3
//                border.color: control.down ? "#17a81a" : "#21be2b"
                border.width: 1
                radius: 2
            }

    }
}

Now when I tried to use my "_myProgress" at the "value: " property in the ProgressBar it only send the first value in the progress and not the rest, so like th efirst 1 or 2% and that's it. In the debug console I can see the progress being calculated in my function at the C++ side but I don't know how this kind of data is supposed to be sent to the QML side. I have seen videos but usually they cover using a C++ class with its own header and cpp files and it sends data to the QML side but all this is inside a QtQuickApplication not a QtWidgetApplication.

[artwaw]

@Kokoy https://doc.qt.io/qt-5/qtqml-cppintegration-overview.html all rather well explained here.

[Kokoy]

appreciate your response