Periodically update data in QML [Solved?]

Kuzma30

I make minimal example project
hub.h

#ifndef Hub_H
#define Hub_H

#include <QObject>
#include <QMap>

class Hub : public QObject
{
    Q_OBJECT
    Q_PROPERTY(QList<double> channelData READ channelData WRITE setChannelData NOTIFY channelDataChanged)
public:
    explicit Hub(QObject *parent = nullptr)
    {
        m_channelData=QList<double>({1,2,3,4,5,6,7,8});
    }
    void setChannelData(QList<double> channelData)
    {
        m_channelData = channelData; //set current data value
    }

    QList<double> channelData()  // return current data list
    {
        return m_channelData;
    }

private:
    QList<double> m_channelData; // list of current datas
signals:
    void channelDataChanged();
};

#endif // Hub_H

main.cpp

#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QQmlContext>
#include <QTimer>
#include <QtDebug>
#include <QRandomGenerator>
#include "Hub/hub.h"

void setItem(QQmlApplicationEngine *pEngine);

Hub channel_1;

int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);

    QQmlApplicationEngine engine;

    engine.rootContext()->setContextProperty("ch", &channel_1);

    engine.load(QUrl(QStringLiteral("qrc:/QML/main.qml")));
    if (engine.rootObjects().isEmpty())
        return -1;

    QTimer timer;
    QObject::connect(&timer, &QTimer::timeout, [&engine]() {
        setItem(&engine);
    });
    timer.start(5000);

    return app.exec();

}

void setItem(QQmlApplicationEngine *pEngine) {
    QList<double> temp;
    for (int i=0;i<8;i++)
    {
     temp.append(QRandomGenerator::global()->bounded(90, 110));
    }
    channel_1.setChannelData(temp);
    qWarning() << "/********************************************************/";
    qWarning() << "Data = " << channel_1.channelData();
}

main.qml

import QtQuick 2.0
Window {
    id: root
    width: 400
    height: 150
    visible: true

    Rectangle {
        id: currentHub
        color: "green"
        border.color: Qt.lighter(color)
        anchors.fill: parent
        Row {
            height: currentHub.height
            width: currentHub.width
            Repeater {
                id: hub_id
                model: 8
                Rectangle {
                    id: oneChartBar
                    anchors.bottom: parent.bottom
                    color: "red"
                    height: ch.channelData[index] === 0?1:ch.channelData[index]
                    width: currentHub.width/8
                    border.width: 1
                    border.color: Qt.lighter(color)
                    Text {
                        id: showchannel
                        anchors.horizontalCenter: oneChartBar.horizontalCenter
                        anchors.bottom: oneChartBar.bottom
                        text: qsTr("%1").arg(index+1)
                        color: "white"
                    }
                }
            }
        }
    }
    Timer {
        interval: 500; running: true; repeat: true
        onTriggered: ch.channelData()
    }

}

Idea is -
channelData is QList <double> (size 8). This is data from 8 sensors. Period of sensor update may changing (not realized in example). On QML side it read initial values for channelData and show as rectangle chart. I want periodically read channelData Qlist values and update charts.
But

 Timer {
        interval: 500; running: true; repeat: true
        onTriggered: ch.channelData()
    }

get error
qrc:/QML/main.qml:40: TypeError: Property 'channelData' of object Hub(0x5555f0d2f4c0) is not a function
qrc:/QML/main.qml:40: TypeError: Type error

P.S.
While writing a post I get solution
Timer in QML must be

    Timer {
        interval: 500; running: true; repeat: true
        onTriggered: ch.channelDataChanged()
    }

If any body have better solution please add it here.

dheerendra

@Kuzma30 said in Periodically update data in QML [Solved?]:

channelData

channelData is Q_PROPERTY. You can directly use it. channelData() method is not Q_INVOKABLE or SLOT. You can't cal it. channelDataChanged() is a signal. No point in calling it.

Summary access channelData property directly like ch.channelData.

Kuzma30

I use it directly. But without Timer it doesn't update charts.

             Repeater {
...
                     height: ch.channelData[index] === 0?1:ch.channelData[index]

JoeCFD

@Kuzma30 said in Periodically update data in QML [Solved?]:

void setChannelData(QList<double> channelData)
{
    m_channelData = channelData; //set current data value
}

No timer is needed.

    void setChannelData(QList<double> channelData)
    {
        if (channelData.size() !=  m_channelData.size() /*or something like contents changed*/  ) {
            m_channelData = channelData; //set current data value
            emit  channelDataChanged(); //to tell qml things have changed for update
        }
    }