Development/Tutorials/Programming Tutorial KDE 4/KDirWatch

Using KDirWatch

If you want your program to be notified upon file changes, use KDirWatch. Here is an example.



*   Copyright (C) 2004 by Thorsten Staerk
*   kde at staerk de
*   This program is free software; you can redistribute it and/or modify  *
*   it under the terms of the GNU General Public License as published by  *
*   the Free Software Foundation; either version 2 of the License, or     *
*   (at your option) any later version.
*   This program is distributed in the hope that it will be useful,
*   but WITHOUT ANY WARRANTY; without even the implied warranty of
*   GNU General Public License for more details.
*   You should have received a copy of the GNU General Public License     *
*   along with this program; if not, write to the
*   Free Software Foundation, Inc.,
*   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  • /

  1. ifndef _KHELLO_H_
  2. define _KHELLO_H_
  1. ifdef HAVE_CONFIG_H
  2. include <config.h>
  3. endif
  1. include <kmainwindow.h>
  2. include <kdirwatch.h>


* @short Application Main Window
* @author Thorsten Staerk <[email protected]>
* @version 0.1

class khello : public KMainWindow {



   KDirWatch dw;
    * Default Constructor
   khello(char* args);
    * Default Destructor
   virtual ~khello();

public slots:

   void slotdirty();


  1. endif // _KHELLO_H_

First we Subclass KXmlGuiWindow on line 7 with with class MainWindow : public KXmlGuiWindow.

Then we declare the constructor with MainWindow(QWidget *parent=0);.

And finally we declare a pointer to the object that will make up the bulk of our program. KTextEdit is a generic richtext editor with some KDE niceties like cursor auto-hiding.


  1. include "mainwindow.h"

MainWindow::MainWindow(QWidget *parent) : KXmlGuiWindow(parent) {

 textArea = new KTextEdit;

} First, of course, on line 1 we have to include the header file containing the class declaration.

On line 5, we initialise our text editor with an object. Then on line 6 we use the built-in setCentralWidget() function which tells the KXmlGuiWindow what should appear in the central section of the window.

Finally, KXmlGuiWindow::setupGUI() is called which does a lot of behind-the-scenes stuff and creates the default menu bars (Settings, Help).

Back to main.cpp

In order to actually run this window, we need to add a few lines in main.cpp:


  1. include <KApplication>
  2. include <KAboutData>
  3. include <KCmdLineArgs>
  1. include "mainwindow.h"

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

 KAboutData aboutData( "tutorial2", 
     "Tutorial2", "1.0", "A simple text area",
     KAboutData::License_GPL, "(c) 2006" );
 KCmdLineArgs::init( argc, argv, &aboutData );
 KApplication app;

 MainWindow* window = new MainWindow();
 return app.exec();

} The only new lines here (compared to Tutorial 1) are 16 and 17. On line 16, we create our MainWindow object and then on line 17, we display it.


The best way to build the program is to use CMake. All that's changed since tutorial 1 is that mainwindow.cpp has been added to the sources list and any tutorial1 has become tutorial2.


project (tutorial2) find_package(KDE4 REQUIRED) include_directories( ${KDE4_INCLUDES} ) set(tutorial2_SRCS main.cpp mainwindow.cpp ) kde4_add_executable(tutorial2 ${tutorial2_SRCS}) target_link_libraries( tutorial2 ${KDE4_KDEUI_LIBS} ${KDE4_KIO_LIBS} )

Kompile it

To compile, link and run it, use:

cmake . && make && ./tutorial2

Moving On

Now you can move on to using KActions.

This page was last edited on 29 June 2011, at 20:54. Content is available under Creative Commons License SA 4.0 unless otherwise noted.