QFileSystemWatcher send fileChanged() signal to a qml slot

[texasRanger]

Hello,

I have a GUI display that shows data values from an external file. I want to be able to update the display whenever the values in the file change. I'm trying to use QFileSystemWatcher fileChanged() to emit a signal to the SLOT in qml that will update the display. I can't seem to figure out the sending of the signal when the file is read.

//readJSON.h
 
class readJSON :public QObject
{
    Q_OBJECT
 
public:
    readJSON();
 
public slots:
    QString readingJson(const QString &name);
 
};
 
 
//main.cpp
 
int main(int argc, char *argv[])
{
 
 
    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
 
    QGuiApplication app(argc, argv);
 
    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);
 
 
 
    QFileSystemWatcher watcher;
    watcher.addPath("data.json");
 
    readJSON* myGlobal = new readJSON();
 
    engine.rootContext()->setContextProperty("myGlobalObject", myGlobal);
 
 
    QObject::connect(&watcher, SIGNAL(fileChanged()),
                     myGlobal, SLOT(updateDisplay()));
 
    engine.load(url);
 
    return app.exec();
}
 
//main.qml
 
Window {
    visible: true
    width: 800
    height: 800
    title: qsTr("Screen Display")
 
 
    DisplaysForm {
 
        function callCPP(text) {
            var dataOne = myGlobalObject.readingJson(text)
            dataOne = parseFloat(dataOne)
 
            return dataOne
        }
 
       function updateDisplay() {
 
            var value = callCPP("Engine_Spd")
            engSpd_txt.text = value
 
            var value1 = callCPP("Engine_Power")
            engPwr_txt.text = value1
       }

//readJSON.h

class readJSON :public QObject
{
    Q_OBJECT

public:
    readJSON();

public slots:
    QString readingJson(const QString &name);

};


//main.cpp

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


    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);

    QGuiApplication app(argc, argv);

    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);



    QFileSystemWatcher watcher;
    watcher.addPath("data.json");

    readJSON* myGlobal = new readJSON();

    engine.rootContext()->setContextProperty("myGlobalObject", myGlobal);


    QObject::connect(&watcher, SIGNAL(fileChanged()),
                     myGlobal, SLOT(updateDisplay()));
    
    engine.load(url);

    return app.exec();
}

//main.qml

Window {
    visible: true
    width: 800
    height: 800
    title: qsTr("Screen Display")


    DisplaysForm {

        function callCPP(text) {
            var dataOne = myGlobalObject.readingJson(text)
            dataOne = parseFloat(dataOne)

            return dataOne
        }

       function updateDisplay() {

            var value = callCPP("Engine_Spd")
            engSpd_txt.text = value

            var value1 = callCPP("Engine_Power")
            engPwr_txt.text = value1
       }

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