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{{Template:I18n/Language Navigation Bar|Development/Tutorials/Saving_and_loading}}
This page was moved [https://develop.kde.org/docs/getting-started/saving_and_loading/ here].
 
{{TutorialBrowser|
 
series=Beginner Tutorial|
 
name=Loading and saving files|
 
pre=[[Development/Tutorials/Using_KActions|Tutorial 3 - KActions]]|
 
next=TODO (milliams)|
 
reading=KIO::{{class|NetAccess}} {{qt|QFile}}
}}
 
==Abstract==
 
Now that we have a basic text editor interface, it's time to make it do something useful.At the most basic a text editor needs to be able to load files from disc, save files that you've created or edited and create new files.
 
KDE provides a number of classes for working with files which make life a lot easier for developers. The KIO library allows you to easily access files through network-transparent protocols as well as providing standard file dialogs.
 
[[image:introtokdetutorial4.png|frame|center]]
 
== The Code ==
 
===main.cpp===
<code cppqt n>
#include <KApplication>
#include <KAboutData>
#include <KCmdLineArgs>
#include "mainwindow.h"
int main (int argc, char *argv[])
{
  KAboutData aboutData( "tutorial4", "tutorial4",
      ki18n("Tutorial 4"), "1.0",
      ki18n("A simple text area which can load and save."),
      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>
<tt>main.cpp</tt> hasn't changed from tutorial 3 except to change any reference to tutorial 3 to tutorial 4.
 
===mainwindow.h===
<code cppqt n>
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
 
#include <KXmlGuiWindow>
#include <KTextEdit>
 
class MainWindow : public KXmlGuiWindow
{
  Q_OBJECT //new from tutorial3
 
  public:
    MainWindow(QWidget *parent=0);
 
  private:
    KTextEdit* textArea;
    void setupActions();
    QString fileName; //new
 
  private slots: //new
    void newFile(); //new
    void openFile(); //new
    void saveFile(); //new
    void saveFileAs(); //new
    void saveFileAs(const QString &outputFileName); //new
};
 
#endif
</code>
Since we want to add the ability to load and save files, we must add the functions which will do the work. Since the functions will be called through Qt's [http://doc.trolltech.com/latest/signalsandslots.html signal/slot] mechanism we must specify that these functions are slots as we do on line 19. Since we are using slots in this header file, we must also add the [http://doc.trolltech.com/latest/qobject.html#Q_OBJECT <tt>Q_OBJECT</tt>] macro.
 
We also want to keep track of the filename of the currently opened file so we create a <tt>{{qt|QString}} fileName</tt>.
 
===mainwindow.cpp===
<code cppqt n>
#include "mainwindow.h"
 
#include <KApplication>
#include <KAction>
#include <KLocale>
#include <KActionCollection>
#include <KStandardAction>
#include <KFileDialog> //new
#include <KMessageBox> //new
#include <KIO/NetAccess> //new
#include <KSaveFile> //new
#include <QTextStream>
MainWindow::MainWindow(QWidget *parent)
    : KXmlGuiWindow(parent),
      fileName(QString()) //new
{
  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());
  KStandardAction::open(this, SLOT(openFile()),
                        actionCollection()); //new
  KStandardAction::save(this, SLOT(saveFile()),
                        actionCollection()); //new
  KStandardAction::saveAs(this, SLOT(saveFileAs()),
                        actionCollection()); //new
  KStandardAction::openNew(this, SLOT(newFile()),
                        actionCollection()); //new
  setupGUI();
}
 
//New from here on
 
void MainWindow::newFile()
{
  fileName.clear();
  textArea->clear();
}
 
void MainWindow::openFile()
{
  QString fileNameFromDialog = KFileDialog::getOpenFileName();
 
  QString tmpFile;
  if(KIO::NetAccess::download(fileNameFromDialog, tmpFile,
        this))
  {
    QFile file(tmpFile);
    file.open(QIODevice::ReadOnly);
    textArea->setPlainText(QTextStream(&file).readAll());
    fileName = fileNameFromDialog;
 
    KIO::NetAccess::removeTempFile( tmpFile );
  }
  else
  {
    KMessageBox::error(this,
        KIO::NetAccess::lastErrorString());
  }
}
 
void MainWindow::saveFile()
{
  if(!fileName.isEmpty())
  {
    saveFileAs(fileName);
  }
  else
  {
    saveFileAs();
  }
}
 
void MainWindow::saveFileAs()
{
  saveFileAs(KFileDialog::getSaveFileName());
}
 
void MainWindow::saveFileAs(const QString &outputFileName)
{
  KSaveFile file(outputFileName);
  file.open();
 
  QByteArray outputByteArray;
  outputByteArray.append(textArea->toPlainText());
  file.write(outputByteArray);
  file.finalize();
  file.close();
 
  fileName = outputFileName;
}
</code>
 
===tutorial4ui.rc===
<code xml n>
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE kpartgui SYSTEM "kpartgui.dtd">
<gui name="tutorial4" version="1">
  <ToolBar name="mainToolBar" >
    <text>Main Toolbar</text>
    <Action name="clear" />
  </ToolBar>
  <MenuBar>
    <Menu name="file" >
      <Action name="clear" />
    </Menu>
  </MenuBar>
</gui>
</code>
This is identical to <tt>tutorial3ui.rc</tt> from tutorial 3 except the <tt>name</tt> has changed to 'tutorial4'. We do not need to add any information about any of the <tt>KStandardAction</tt>s since the placement of those actions is handled automatically by KDE.
 
==Explanation==
 
==Make, Install And Run==
 
===CMakeLists.txt===
<code>
project(tutorial4)
find_package(KDE4 REQUIRED)
include_directories(${KDE4_INCLUDES})
set(tutorial4_SRCS
  main.cpp
  mainwindow.cpp
)
kde4_add_executable(tutorial4 ${tutorial4_SRCS})
target_link_libraries(tutorial4 ${KDE4_KDEUI_LIBS} ${KDE4_KIO_LIBS})
install(TARGETS tutorial4 DESTINATION ${BIN_INSTALL_DIR})
install(FILES tutorial4ui.rc
        DESTINATION ${DATA_INSTALL_DIR}/tutorial4)
</code>
Since we are now using the KIO library, we must tell CMake to link against it. We do this by passing <tt>${KDE4_KIO_LIBS}</tt> to the <tt>target_link_libraries()</tt> function.
 
With this file, the tutorial can built and run in the same way as tutorial 3. For more information, see tutorial 3.
 
mkdir build && cd build
cmake .. -DCMAKE_INSTALL_PREFIX=$HOME
make install
$HOME/bin/tutorial4

Latest revision as of 14:34, 8 September 2020

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