KeyPressEvent

ApprenticeReno

Hi guys
So i have this code where i try to press delete from my keyboard and expect the program to catch this event and do something like a MessageBox or a qDebug.
It doesn't give me error but doesn't work either.
I don't understand what i'm doing wrong.

Main Window.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QTableWidget>
#include <QTableWidgetItem>
#include <QListWidgetItem>
#include <QKeyEvent>
#include <QMessageBox>

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);

private slots:

void on_keyPressEvent(QKeyEvent *event);

private:
    Ui::MainWindow *ui;

};
#endif // MAINWINDOW_H

Main Window .cpp

void MainWindow::on_keyPressEvent(QKeyEvent *event){
    if(event->key() == Qt::Key_Delete){
       QMessageBox::information(this,"Hello","You Have pressed delete");
       qDebug()<<"do some code here ";
    }

If anyone knows what's missing i would really appreciate some help, thanks.

jsulm

@ApprenticeReno Key press event (as its name suggests) is an event, not a signal. So, you need to override the https://doc.qt.io/qt-6/qwidget.html#keyPressEvent method in your subclass.

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);

protected:   
    void keyPressEvent(QKeyEvent *event) override;

See also https://doc.qt.io/qt-6/eventsandfilters.html

ApprenticeReno

@jsulm I thought there was no difference between a signal and an event, my bad.

//mainwindow.h

protected:
void keyPressEvent(QKeyEvent *event) override;

And

//mainwindow.cpp

void MainWindow::keyPressEvent(QKeyEvent *event){

if(event->key() == Qt::Key_Delete){

QMessageBox::information(this,"hello","you pressed delete");
}

}

Tried this way and it works. @jsulm Thank you very much.

JonB

@ApprenticeReno
Qt uses a convention that if a method name ends in Event it is a virtual method you can override, and not a signal/slot. There has long been debate about which "happenings" should be "events" versus "signals", not for you to worry, just keep an eye out for that Event in the name :)