Development/Tutorials/KDE2/KHello/Tutorial 2

Description

In this step I describe how a window class is created.

Source code

Now there are three files

/************* khello.h *******************/
#include <kapp.h>
#include <kmainwindow.h>

class KHello : public KMainWindow
{
  Q_OBJECT
public:
  void closeEvent(QCloseEvent *);
};

/************* khello.cc ******************/
#include "khello.moc"

void KHello::closeEvent(QCloseEvent *e)
{
  kapp->beep();
  KMainWindow::closeEvent(e);
}

/************* main.cc ********************/
#include "khello.h"

int main( int argc, char **argv )
{
  KApplication a( argc, argv, "khello" );
  KHello *w = new KHello();
  w->setGeometry(100,100,200,100);

  a.setMainWidget( w );
  w->show();
  return a.exec();
}

Explaining the code

There are a few commands that need explaining:

Q_OBJECT

This is a command to the meta object compiler, which is included in the developer files for QT. You must start each KDE class with this line.

void closeEvent(QCloseEvent *);

This function is called when your window is being closed. We sound a beep when that happens and then call the original closeEvent() function. The original closeEvent() function takes care to exit the application when the last window gets closed.

#include "khello.moc"

The meta object compiler produces a moc file, which you must include. The moc file is an extended version of your header file.

Compiling

[on linux where KDEDIR and QTDIR contain the paths to where KDE and Qt are installed respectively] [FreeBSD 5.x users may omit the -ldl]

g++ -c -I$KDEDIR/include -I$QTDIR/include -fno-rtti main.cc
moc khello.h -o khello.moc
g++ -c -I$KDEDIR/include -I$QTDIR/include -fno-rtti khello.cc
g++ -L$KDEDIR/lib -L$QTDIR/lib -lkdeui -lkdecore -lqt -ldl -o khello main.o khello.o

[if moc is not in your path try $QTDIR/bin/moc]