Development/Tutorials/Using KActions: Difference between revisions

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This page was moved [https://develop.kde.org/docs/getting-started/kxmlgui/using_actions/ here]
 
{{TutorialBrowser|
 
series=Beginner Tutorial|
 
name=How To Use KActions and XMLGUI|
 
pre=[[Development/Tutorials/Using_KXmlGuiWindow|Tutorial 2 - KXmlGuiWindow]], Basic XML knowledge|
 
next=[[Development/Tutorials/Saving_and_loading|Tutorial 4 - Saving and loading]]|
 
reading=None
}}
 
==Abstract==
This tutorial introduces the concept of actions. Actions are a unified way of supplying the user with ways to interact with your program.
 
For example, if we wanted to let the user of [[Development/Tutorials/Using_KXmlGuiWindow|Tutorial 2 ]] clear the text box by clicking a button in the toolbar, from an option in the File menu or through a keyboard shortcut, it could all be done with one {{class|KAction}}.
 
[[image:introtokdetutorial3.png|frame|center]]
 
==KAction==
A {{class|KAction}} is an object which contains all the information about the icon and shortcuts that is associated with a certain action. The action is then connected to a [http://doc.trolltech.com/latest/signalsandslots.html slot] which carries out the work of your action.
 
== The Code ==
 
===main.cpp===
<code cppqt>
#include <KApplication>
#include <KAboutData>
#include <KCmdLineArgs>
 
#include "mainwindow.h"
 
int main (int argc, char *argv[])
{
  KAboutData aboutData( "tutorial3", "tutorial3",
      ki18n("Tutorial 3"), "1.0",
      ki18n("A simple text area using KAction etc."),
      KAboutData::License_GPL,
      ki18n("Copyright (c) 2007 Developer") );
  KCmdLineArgs::init( argc, argv, &aboutData );
  KApplication app;
  MainWindow* window = new MainWindow();
  window->show();
  return app.exec();
}
</code>
This time, very little has changed in <tt>main.cpp</tt>, only the KAboutData constructor has been updated to show that we are now on tutorial 3.
 
===mainwindow.h===
<code cppqt>
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
 
#include <KXmlGuiWindow>
#include <KTextEdit>
 
class MainWindow : public KXmlGuiWindow
{
  public:
    MainWindow(QWidget *parent=0);
  private:
    KTextEdit* textArea;
    void setupActions();
};
 
#endif
</code>
Only a function <tt>void setupActions()</tt> has been added which will do all the work setting up the KActions.
 
===mainwindow.cpp===
<code cppqt>
#include "mainwindow.h"
 
#include <KApplication>
#include <KAction>
#include <KLocale>
#include <KActionCollection>
#include <KStandardAction>
 
MainWindow::MainWindow(QWidget *parent)
    : KXmlGuiWindow(parent)
{
  textArea = new KTextEdit;
  setCentralWidget(textArea);
 
  setupActions();
}
 
void MainWindow::setupActions()
{
  KAction* clearAction = new KAction(this);
  clearAction->setText(i18n("Clear"));
  clearAction->setIcon(KIcon("document-new"));
  clearAction->setShortcut(Qt::CTRL + Qt::Key_W);
  actionCollection()->addAction("clear", clearAction);
  connect(clearAction, SIGNAL(triggered(bool)),
          textArea, SLOT(clear()));
 
  KStandardAction::quit(kapp, SLOT(quit()),
                        actionCollection());
 
  setupGUI();
}
</code>
 
==Explanation==
This builds upon the KXmlGuiWindow code from [[Development/Tutorials/Using_KXmlGuiWindow|Tutorial 2]]. Most of the changes are to <tt>mainwindow.cpp</tt>, an important structural change being that the constructor for MainWindow now calls <tt>setupActions()</tt> instead of <tt>setupGUI()</tt>. <tt>setupActions()</tt> is where the new KAction code goes before finally calling <tt>setupGUI()</tt> itself.
 
===Creating the KAction object===
The KAction is built up in a number of steps. The first is including the <tt>KAction</tt> library and then creating the KAction:
<code cppqt>
#include <KAction>
...
KAction* clearAction = new KAction(this);
</code>
This creates a new KAction called <tt>clearAction</tt>.
 
===Setting KAction Properties===
====Text====
Now we have our KAction object, we can start setting its properties. The following code sets the text that will be displayed in the menu and under the <tt>KAction</tt>'s icon in the toolbar.
<code cppqt>clearAction->setText(i18n("Clear"));</code>
Note that the text is passed through the i18n() function; this is necessary for the UI to be translatable (more information on this can be found in the [[Development/Tutorials/Localization/i18n|i18n tutorial]]).
 
====Icon====
If the action is going to be displayed in a toolbar, it's nice to have an icon depicting the action. The following code sets the icon to the standard KDE <tt>document-new</tt> icon through the use of the <tt>setIcon()</tt> function:
<code cppqt>clearAction->setIcon(KIcon("document-new"));</code>
 
====Keyboard Shortcut====
Setting a keyboard shortcut to perform our action is equally simple:
<code cppqt>clearAction->setShortcut(Qt::CTRL + Qt::Key_W);</code>
This associates Ctrl+W with the KAction.
 
===Adding to the Collection===
In order for the action to be accessed by the XMLGUI framework (explained in depth later) it must be added to the application's ''action collection''. The action collection is accessed via the <tt>actionCollection()</tt> function like this:
<code cppqt>
actionCollection()->addAction("clear", clearAction);
</code>
Here, the <tt>clearAction</tt> KAction is added to the collection and given a name of ''clear''. This name (''clear'') is used by the XMLGUI framework to refer to the action, ergo, it should not be localized, since it is used internally only.
 
====Connecting the action====
Now that the action is fully set up, it needs to be connected to something useful. In this case (because we want to clear the text area), we connect our action to the <tt>clear()</tt> action belonging to a KTextEdit (which, unsurprisingly, clears the KTextEdit)
<code cppqt>
connect( clearAction, SIGNAL( triggered(bool) ),
        textArea, SLOT( clear() ) );
</code>
This is the same as it would be done in Qt with a {{qt|QAction}}.
 
===KStandardAction===
 
For actions which would likely appear in almost every KDE application such as 'quit', 'save', and 'load' there are pre-created convenience KActions, accessed through [http://api.kde.org/4.0-api/kdelibs-apidocs/kdeui/html/namespaceKStandardAction.html KStandardAction].
 
They are very simple to use. Once the library has been included (<tt>#include <KStandardAction></tt>), simply supply it with what you want the function to do and which KActionCollection to add it to. For example:
<code cppqt>KStandardAction::quit(kapp, SLOT(quit()), actionCollection());</code>
This creates a KAction with the correct icon, text and shortcut and even adds it to the File menu.
 
==Adding the action to menus and toolbars==
At the moment, the new "Clear" action has been created but it hasn't been associated with any menus or toolbars. This is done with a KDE technology called XMLGUI, which does nice things like movable toolbars for you.
 
{{note|In a later version of KDE4, XMLGUI, may be replaced with a new framework called liveui. For now, XMLGUI, is the only and correct way to set up the UI.}}
 
==XMLGUI==
 
The <tt>setupGUI()</tt> function in {{class|KXmlGuiWindow}} depends on the XMLGUI system to construct the GUI, which XMLGUI does by parsing an XML file description of the interface.
 
The rule for naming this XML file is <tt>appnameui.rc</tt>, where <tt>appname</tt> is the name you set in {{class|KAboutData}} (in this case, ''tutorial3''). So in our example, the file is called <tt>tutorial3ui.rc</tt>, and is located in the build directory. Where the file will ultimately be placed is handled by CMake.
 
==''appname''ui.rc File==
 
Since the description of the UI is defined with XML, the layout must follow strict rules. This tutorial will not go into great depth on this topic, but for more information, see the [[Development/Architecture/KDE4/XMLGUI_Technology|detailed XMLGUI page]] (here is an older tutorial: [http://developer.kde.org/documentation/tutorials/xmlui/preface.html]).
 
===tutorial3ui.rc===
<code xml>
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE kpartgui SYSTEM "kpartgui.dtd">
<gui name="tutorial3" version="1">
  <ToolBar name="mainToolBar" >
    <text>Main Toolbar</text>
    <Action name="clear" />
  </ToolBar>
  <MenuBar>
    <Menu name="file" >
      <Action name="clear" />
    </Menu>
  </MenuBar>
</gui>
</code>
 
The <tt><Toolbar></tt> tag allows you to describe the toolbar, which is the bar across the top of the window normally with icons. Here it is given the unique name ''mainToolBar'' and its user visible name set to ''Main Toolbar'' using the <tt><text></tt> tag. The clear action is added to the toolbar using the <tt><Action></tt> tag, the name parameter in this tag being the string that was passed to the KActionCollection with <tt>addAction()</tt> in <tt>mainwindow.cpp</tt>.
 
Besides having the action in the toolbar, it can also be added to the menubar. Here the action is being added to the ''File'' menu of the <tt>MenuBar</tt> the same way it was added to the toolbar.
 
Change the 'version' attribute of the <tt><nowiki><gui></nowiki></tt> tag if you changed .rc file since the last install to force a system cache update.
 
Some notes on the interaction between code and the .rc file: Menus appear automatically and should have a <tt><nowiki><text/></nowiki></tt> child tag unless they refer to standard menus. Actions need to be created manually and inserted into the actionCollection() using the name in the .rc file. Actions can be hidden or disabled, whereas menus can't.
 
==CMake==
Finally, the <tt>tutorial3ui.rc</tt> needs to go somewhere where KDE can find it (can't just leave it in the source directory!). '''This means the project needs to be installed somewhere.'''
===CMakeLists.txt===
<code ini n>
project(tutorial3)
 
find_package(KDE4 REQUIRED)
include_directories(${KDE4_INCLUDES})
 
set(tutorial3_SRCS
  main.cpp
  mainwindow.cpp
)
 
kde4_add_executable(tutorial3 ${tutorial3_SRCS})
 
target_link_libraries(tutorial3 ${KDE4_KDEUI_LIBS})
 
install(TARGETS tutorial3 DESTINATION ${BIN_INSTALL_DIR})
install(FILES tutorial3ui.rc
        DESTINATION  ${DATA_INSTALL_DIR}/tutorial3)
</code>
 
This file is almost identical to the one for tutorial2, but with two extra lines at the end that describe where the files are to be installed. Firstly, the <tt>tutorial3</tt> target is installed to the <tt>BIN_INSTALL_DIR</tt> then the <tt>tutorial3ui.rc</tt> file that describes the layout of the user interface is installed to the application's data directory.
 
===Make, Install And Run===
If you don't have write access to where your KDE4 installation directory, you can install it to a folder in your home directory.
 
To tell CMake where to install the program, set the <tt>DCMAKE_INSTALL_PREFIX</tt> switch. You probably just want to install it somewhere local for testing (it's probably a bit silly to go to the effort of installing these tutorials to your KDE directory), so the following might be appropriate:
mkdir build && cd build
cmake .. -DCMAKE_INSTALL_PREFIX=$HOME
make install
$HOME/bin/tutorial3
which will create a KDE-like directory structure in your user's home directory directory and will install the executable to {{path|$HOME/bin/tutorial3}}.
 
==Moving On==
Now you can move on to [[Development/Tutorials/Saving_and_loading|saving and loading]].
 
[[Category:C++]]

Latest revision as of 14:15, 18 July 2023

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