[SOLVED] Detect QKeyEvent in every children of a QWidget

Max13

I'm on a "cash register" app for family business. I have a barcode scanner, touch-screen and a USB numeric keypad.

In my "cash register" widget, there is few buttons and a QTableView (to show the cart). I need to detect when either "+, -, *, /" keys are pressed, but also any other.

These 4 keys are "actions" ("plus" will show a list, "minus" will delete the last product, etc...) and any other key (mostly numeric) will show a dialog with a QLineEdit containing any pressed keys until "enter" is pressed (automatically sent by the barcode scanner) to validate a scan or a manual barcode.

When I've reimplemented MyWidget::keyPressEvent(), it was only detected when the focus was on MyWidget, and the problem is that when you press a button (MyWidget's child) you set the focus on the button, same if you select a line in the QTableView. Is there an efficient way to reimplement keyPressEvent() in the parent widget to listen for all the children's keyPressEvents?

I tried with QShortcut (as Qt::WindowShortcut) which is fine but I can't detect every other keys. Any idea?

SGaist

Hi,

What about an eventFilter that you put on your widgets ?

Max13

I'll give a try.
Actually, I thought I would have the same problem with eventFilter (concerning the focus) or maybe you're telling me I will have to install the same eventFilter on every child of my QWidget?

Max13

Ok... This is strange. The filter successfully detects keyPresses in the widget, no matter which one is focused (between children). But I don't understand why, it only detects modifiers keys :/

@class CashRegisterEventFilter : public QObject
{
protected:
bool eventFilter(QObject *obj, QEvent *event)
{
if (event->type() == QEvent::KeyPress) {
QKeyEvent *keyEvent = static_cast<QKeyEvent *>(event);
qDebug() << "Key pressed:" << (Qt::Key) keyEvent->key();
return (true);
}

        return QObject::eventFilter(obj, event);
    }

public:
    CashRegisterEventFilter(QObject *parent) : QObject(parent) {}

};@

Then:

@this->m_eventFilter = new CashRegisterEventFilter(this);
this->installEventFilter(this->m_eventFilter);@

Debug only shows something when I press "Alt", "Shift", "cmd"... I'm on OS X 10.10.2, any idea?

Max13

NEVERMIND !

Thank you, it's my view's fault. The view already captures the alphanumerical key presses.

I'm implementing with eventFilter, it seems to be working as expected.

SGaist

Out of curiosity, are you using several CashRegisterEventFilter ?