(C++) How to define a OnKeyPress Event?

 

How to define a OnKeyPress Event? is a QT FAQ for if you want to respond to key presses/releases.

 

 

 

 

 

Project and source code

 

Operating system: Ubuntu 10.04 LTS Lucid Lynx

IDE: Qt Creator 2.0.0

Project type: Qt4 GUI Application

Compiler: G++ 4.4.1

Libraries used:

• Qt: version 4.7.0 (32 bit)

 

• View a screenshot of 'CppQtOnKeyPress' (png)
• Download the Qt Creator project 'CppQtOnKeyPress' (zip)

 

 

 

 

 

main.cpp

 

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#include <QApplication> #include "dialog.h" int main(int argc, char *argv[]) {   QApplication a(argc, argv);   Dialog w;   w.show();   return a.exec(); }

 

 

 

 

 

dialog.h

 

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#ifndef DIALOG_H #define DIALOG_H #include <QDialog> struct QKeyEvent; namespace Ui {   class Dialog; } class Dialog : public QDialog {   Q_OBJECT public:   explicit Dialog(QWidget *parent = 0);   ~Dialog(); protected:   void changeEvent(QEvent *e); private:   Ui::Dialog *ui; private slots:   void keyPressEvent(QKeyEvent * e);   void keyReleaseEvent(QKeyEvent * e); }; //From http://www.richelbilderbeek.nl/CppIntToQtStr.htm QString IntToQtStr(const int i); #endif // DIALOG_H

 

 

 

 

 

dialog.cpp

 

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#include <QKeyEvent> #include "dialog.h" #include "ui_dialog.h" Dialog::Dialog(QWidget *parent) :     QDialog(parent),     ui(new Ui::Dialog) {   ui->setupUi(this); } Dialog::~Dialog() {   delete ui; } void Dialog::changeEvent(QEvent *e) {     QDialog::changeEvent(e);     switch (e->type()) {     case QEvent::LanguageChange:         ui->retranslateUi(this);         break;     default:         break;     } } void Dialog::keyPressEvent(QKeyEvent * e) {   switch (e->type())   {     case QEvent::KeyPress:       ui->text_edit->appendPlainText("Key pressed: " + IntToQtStr(e->key()));       break;     default:       break;   } } void Dialog::keyReleaseEvent(QKeyEvent * e) {   switch (e->type())   {     case QEvent::KeyRelease:       ui->text_edit->appendPlainText("Key released: " + IntToQtStr(e->key()));       break;     default:       break;   } } //From http://www.richelbilderbeek.nl/CppIntToQtStr.htm QString IntToQtStr(const int i) {   QString s;   s.setNum(i);   return s; }