Development/Tutorials/First program

Your first program shall greet the world with a friendly "hello world", what else ? For that, we will use a KMessageBox. To get more information about the KMessageBox-Class, type "kde: kmessagebox" in your konqueror and it will redirect you to http://developer.kde.org/documentation/library/cvs-api/kdelibs-apidocs/kdeui/html/classKMessageBox.html

1. include <QString>
2. include <kapplication.h>
3. include <kaboutdata.h>
4. include <kmessagebox.h>
5. include <kcmdlineargs.h>

int main (int argc, char *argv[]) {

KAboutData aboutData( "test", "test",
                      "1.0", "test", KAboutData::License_GPL,
                      "(c) 2006" );
KCmdLineArgs::init( argc, argv, &aboutData );
KApplication khello;
KGuiItem kgi( QString( "Hello" ), QString(),
              QString( "this is a tooltip" ),
              QString( "this is whatsthis" ) );
KMessageBox::questionYesNo( 0, "text", "caption", kgi );

} If you set up your environment as described in Build/Unstable Version, you can compile this code with

gcc hello.cpp -o hello -I/home/kde-devel/qt-unstable/include/Qt \
-I/home/kde-devel/qt-unstable/include/Qt-Core \
-I/home/kde-devel/qt-unstable/include -I/home/kde-devel/kde/include \
-L/home/kde-devel/kde/lib \
-L/home/kde-devel/qt-unstable/lib -lkdeui -lkdecore -ldl 

and then run it with

./hello

If that worked, you may want to use cmake, just like the rest of KDE. Create a file named CMakeLists.txt with this content:

1. name of the project

project (hello)

1. find and use the necessary libraries and headers

find_package(KDE4 REQUIRED) include_directories( ${KDE4_INCLUDES} )

1. compile
2. using a variable is not really necessary:
3. using the single line
4. kde4_add_executable(hello hello.cpp)
5. does the same, but when you add more stuff to the project,
6. using the variable makes things a bit easier.

set(helloSources hello.cpp) kde4_add_executable(hello ${helloSources})

1. and link properly

target_link_libraries( hello ${KDE4_KDEUI_LIBS} ${KDE4_KIO_LIBS})

Tip

Note: This page is about KDE 4. It isn't applicable for KDE 3 development.