Development/Tutorials/KDE2/KHello/Tutorial 3

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. <syntaxhighlight lang="cpp-qt" line> /************* khello.h *******************/

1. include <kapp.h> // From KHello2
2. include <kmainwindow.h> // From KHello2
3. 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;

}; <syntaxhighlight lang="cpp-qt" line> /************* khello.cc ******************/

1. include "khello.moc" // From KHello2
2. 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. <syntaxhighlight lang="cpp-qt"> 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. <syntaxhighlight lang="cpp-qt"> 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]