Development/Tutorials/KDE2/KHello/Tutorial 3

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Description

Now is the time to add a few buttons.

Source code

The old code is gray. I have not included main.cc below, because it is the same as in KHello #2.

/************* khello.h *******************/
#include <kapp.h>                 // From KHello2
#include <kmainwindow.h>          // From KHello2
#include <qpushbutton.h>

class KHello : public KMainWindow // From KHello2
{                                 //  |
  Q_OBJECT                        //  |
public:                           // From KHello2
  KHello();
  void closeEvent(QCloseEvent *); // From KHello2
public slots:
  void slotHello();
  void slotExit();
private:
  QPushButton *btnHello;
  QPushButton *btnExit;
};

/************* khello.cc ******************/
#include "khello.moc"             // From KHello2
#include <kmessagebox.h>

KHello::KHello() : KMainWindow()
{
  btnHello = new QPushButton("Hello", this);
  btnHello->setGeometry(45,30,50,25);
  btnHello->show();
  connect(btnHello, SIGNAL(clicked()), this, SLOT(slotHello()));
  
  btnExit = new QPushButton("Exit", this);
  btnExit->setGeometry(105,30,50,25);
  btnExit->show();
  connect(btnExit, SIGNAL(clicked()), this, SLOT(slotExit()));  
}

void KHello::closeEvent(QCloseEvent *e) // From KHello2
{                                       //  |
  kapp->beep();                         //  |
  KMainWindow::closeEvent(e);           //  |
}                                       // From KHello2

void KHello::slotHello()
{
  KMessageBox::messageBox(0, KMessageBox::Information, "Hello World!");
}

void KHello::slotExit()
{
  close();
}

Explaining the code

I'll only explain what I believe is necessary this time.

public slots:

This section is new, and it used by the meta object compiler. In the QT world, slots are event-handlers and signals are events. Put all your event handlers in this section.

connect(btnHello, SIGNAL(clicked()), this, SLOT(slotHello()));

Connect the event "clicked" from the btnHello object to the event handler "slotHello".

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]