Barcode Scanner - Keyboard vs VirtualCOM

[Damian7546]

Hi,
In my Qt application I am using barcode scanner. Until today I use barcode scanner with USB interface working as virtual com port. The application was simple. it opened port and when there was signal readyread then after that i did my logic.
Now I have barcode scanner with USB interface but working as keyboard.
How applied this barcodescanner to my applcation ? How emit any signal in my logic when barcode read any code ?

[J.Hilk]

@Damian7546 have you tried giving a textedit active focus when you try to scan something?

[Damian7546]

@J-Hilk Yes in this way work. But I don't have gui. Only console application.

Moreover I use QML.

maybe it is possible use in QML :

Shortcut {
        sequence: "Q,E"
        context: Qt.ApplicationShortcut


    }

And if my code will be beginning from QE chars then save to all form keyboard to variable, only how to do it ?

[J.Hilk]

@Damian7546 I would rather go with an custom event filter and listen for QKeyEvents

you can and should install the event filter on your QCoreApplication that should get all the key events.

[Damian7546]

@J-Hilk How do this ?

[J.Hilk]

@Damian7546 follow the links, they are with example even.

[Damian7546]

I am beginner I do not know how event filter would work with a barcode scanner

[J.Hilk]

@Damian7546

something like this.

class MyKeyEventFilter : public QObject
{
    Q_OBJECT
public:
    MyKeyEventFilter(QObject *parent = nullptr) : QObject(parent) {}

    bool eventFilter(QObject *object, QEvent *event) override {
        Q_UNUSED(object);
        if(event->type() == QEvent::KeyPress || event->type() == QEvent::KeyRelease){
            qDebug() << static_cast<QKeyEvent *>(event)->key();
        }

        return false; // <-- Do not swallow the event
    }
};

int main(int argc, char *argv[])
{
    QApplication app(argc,argv);
    app.installEventFilter(new MyKeyEventFilter());

    QWidget w ;
    w .show();
    
    return app.exec();
}

not sure if it will work for your hardware.

Only console application.

Moreover I use QML.

this is a contradiction.

I am beginner I do not know how event filter would work with a barcode scanner

thats not an excuse and one has nothing to do with the other. I know even less about your barcode scanner than you do and can only offer suggestions

[Damian7546]

This post is deleted!

[Damian7546]

@ I did like you said with only little change, like below:

bool MyKeyEventFilter::eventFilter(QObject *object, QEvent *event)
{
    Q_UNUSED(object);
    if(event->type() == QEvent::KeyPress){
        if(test.count() >= 12 )
        {
            qDebug() << test;
            test.clear();
            return true;
        }
        else
        {
            test.append(static_cast<QKeyEvent *>(event)->text());
            return false;
        }


    }
    return false; // <-- Do not swallow the event
}

Works, but after two times scanned the solution is:
555777---555
222000111---

but it should be

57-57201-N-3
57-57201-N-3

each letter are repeat 3 times, why ?

[Damian7546]

This post is deleted!

[Damian7546]

@J-Hilk
Works great with little filter. Below solution for posterity:

bool MyKeyEventFilter::eventFilter(QObject *object, QEvent *event)
{

    Q_UNUSED(object);
    if(event->type() == QEvent::KeyPress){

        if(static_cast<QKeyEvent *>(event)->key() == Qt::Key_Return)
        {
            qDebug() << test;
            test.clear();
            return true;
        }

        else if (!m_Timeout)
        {
            m_Timeout=true;
            test.append(static_cast<QKeyEvent *>(event)->text());
            timDelay.start(1);
            return false;
        }
        else
        {
            return false;
        }
    }
    return false;
}