Implemented a QKeyEvent but how does the keyPressEvent() gets called

Question

keypress.h

#ifndef KEYPRESS_H
#define KEYPRESS_H

#include <QObject>
#include <QKeyEvent>

class keypress : public QObject {
    Q_OBJECT public:
    explicit keypress(QObject *parent = nullptr);
    void keyPressEvent(QKeyEvent *e);

};

#endif // KEYPRESS_H

keypress.cpp

#include "keypress.h"
#include <QDebug>

keypress::keypress(QObject *parent)
    : QObject{parent}
{

}

void keypress::keyPressEvent(QKeyEvent *e)
{
    qDebug() <<"Key clicked : "<<e->key();
}

I am new to QKeyEvent and I am not able to call the keyPressEvent function. Should i call the keyPressEvent function inside the constructor? I also have to display a connect with keyPressEvent function and a timer of 50 milli seconds even if it doesn't receive any keypress. Thanks in Advance!

Answer 1

If you want to implement keyPressEvent in the widget/dialog/control, you can override keyPressEvent.

Here is another link:

• QWidget keyPressEvent override

if you want to implement key press yourself and installed on other widgets, you can refer to the code below,

From QObject::installEventFilter,

class KeyPressEater : public QObject
{
    Q_OBJECT
    ...

protected:
    bool eventFilter(QObject *obj, QEvent *event) override;
};

bool KeyPressEater::eventFilter(QObject *obj, QEvent *event)
{
    if (event->type() == QEvent::KeyPress) {
        QKeyEvent *keyEvent = static_cast<QKeyEvent *>(event);
        qDebug("Ate key press %d", keyEvent->key());
        return true;
    } else {
        // standard event processing
        return QObject::eventFilter(obj, event);
    }
}

And here's how to install it on two widgets:

KeyPressEater *keyPressEater = new KeyPressEater(this);
QPushButton *pushButton = new QPushButton(this);
QListView *listView = new QListView(this);

pushButton->installEventFilter(keyPressEater);
listView->installEventFilter(keyPressEater);

Hope it helps you.