Difference between revisions of "Development/Tutorials/First program"

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{{TutorialBrowser|Beginner Tutorial|C++, Qt, [[Getting_Started/Build/Unstable_Version|KDE4 development environment]]|[[Development/Tutorials/Programming_Tutorial_KDE_4/Using_KMainWindow|Tutorial 2 - KMainWindow]]| CMake }}
This [https://develop.kde.org/docs/getting-started/hello_world/ first program] page was move [https://develop.kde.org/docs/getting-started/hello_world/ here].
Your first program shall greet the world with a friendly "Hello World", what else? For that, we will use a {{class|KMessageBox}}.
{{tip|To get more information about any class you come across, Konqueror offers a quick shortcut. So to look for information about KMessageBox, just type "kde:kmessagebox" into Konqueror and you'll be taken to the documentation.}}
* C++
* Qt
* KDE4 development environment
==The Code==
All the code we need will be in one file, <tt>main.cpp</tt>. Create that file with the code below:
<code cppqt n>
#include <QString>
#include <KApplication>
#include <KAboutData>
#include <KMessageBox>
#include <KCmdLineArgs>
int main (int argc, char *argv[])
  KAboutData aboutData( "tutorial1", "Tutorial 2",
                        "1.0", "KMessageBox popup",
                        KAboutData::License_GPL, "(c) 2006" );
  KCmdLineArgs::init( argc, argv, &aboutData );
  KApplication app;
  KGuiItem guiItem( QString( "Hello" ), QString(),
                    QString( "this is a tooltip" ),
                    QString( "this is a whatsthis" ) );
  KMessageBox::questionYesNo( 0, "Hello World",
                              "Hello", guiItem );
The first KDE specific code we come across in this program is {{class|KAboutData}}. This is the class used to store information about the program such as a short description, authors or license information. Pretty much every KDE application should use this class.
Then we come to {{class|KCmdLineArgs}}. This is the class one would use to specify command line switches to, for example, open the program with a specific file. However, in this tutorial, we simply initialise it with the {{class|KAboutData}} object we created so we can use the <tt>--version</tt> or <tt>--author</tt> switches.
On line 13 we create a {{class|KApplication}} object. This needs to be done exactly once in each program since it is needed for things such as [[Development/Tutorials/i18n|i18n]].
Now we've done all the necessary KDE setup, we can move on to doing interesting things with our application. We're going to create a popup box but we're going o customise one of the buttons. To do this customisation, we create a {{class|KGuiItem}} object. The first argument in the {{class|KGuiItem}} constructor is the text that will appear on the item (in our case, a button). Then we have an option of setting an icon for the button but we don't want one so we just give it <tt>QString()</tt>. Finally we set the tooltip (what appears when you hover over an item) and the "What's This?" (accessed through right-clicking or Shift-F1) text.
Now we have our item, we can create out popup. we call the <tt>KMessageBox::questionYesNo()</tt> function which, by default, creates a message box with a "Yes" and a "No" button. The second argument is the text that will appear in the middle of the popup box. Then we set the caption the window will have and finally we set the KGuiItem for (what would normally be) the "Yes" button to the <tt>guiItem</tt> we created.
We're all done as far as the code is concerned. Now to build it and try it out.
If you set up your environment as described in [[Getting_Started/Build/Unstable_Version|Getting_Started/Build/Unstable_Version]], you can compile this code with
gcc main.cpp -o tutorial1 \
-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
===Using CMake===
If that worked, you may want to use CMake, just like the rest of KDE.
Create a file named CMakeLists.txt in the same directory as main.cpp with this content:
#name of the project
project (tutorial1)
#find and use the necessary libraries and headers
find_package(KDE4 REQUIRED)
include_directories( ${KDE4_INCLUDES} )
# compile
# using a variable is not really necessary:
# using the single line
# kde4_add_executable(tutorial1 main.cpp)
# does the same, but when you add more stuff to the project,
# using the variable makes things a bit easier.
set(tutorial1_SRCS hello.cpp)
kde4_add_executable(tutorial1 ${helloSources})
# and link properly
target_link_libraries(tutorial1 ${KDE4_KDEUI_LIBS})
====Make And Run====
Then it's simply a case of doing (from the directory where main.cpp is)
cmake .
==Moving On==
Now you can move on to [[Development/Tutorials/Programming_Tutorial_KDE_4/Using_KMainWindow|using KMainWindow]].

Latest revision as of 14:30, 8 September 2020

This first program page was move here.

This page was last edited on 8 September 2020, at 14:30. Content is available under Creative Commons License SA 4.0 unless otherwise noted.