Development/Tutorials/KCmdLineArgs

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    Command line arguments
    Tutorial Series   Beginner Tutorial
    Previous   Tutorial 4 - Loading and saving
    What's Next   n/a
    Further Reading   n/a


    Abstract

    Now that we have a text editor which can open and save files. We will now make the editor act more like a desktop application by enabling it to open files from command line arguments or even using Open with from within Dolphin.

    The Code

    main.cpp

    #include <cstdlib>
     
    #include <QApplication>
    #include <QCommandLineParser>
    #include <QUrl>
    #include <QDir>
    
    #include <KAboutData>
    #include <KLocalizedString>
    
    #include "mainwindow.h"
     
    int main (int argc, char *argv[])
    {
        QApplication app(argc, argv);
        
        KLocalizedString::setApplicationDomain("tutorial5");
        
        KAboutData aboutData(
                             // The program name used internally. (componentName)
                             QStringLiteral("tutorial5"),
                             // A displayable program name string. (displayName)
                             i18n("Tutorial 5"),
                             // The program version string. (version)
                             QStringLiteral("1.0"),
                             // Short description of what the app does. (shortDescription)
                             i18n("A simple text area which can load and save."),
                             // The license this code is released under
                             KAboutLicense::GPL,
                             // Copyright Statement (copyrightStatement = QString())
                             i18n("(c) 2015"),
                             // Optional text shown in the About box.
                             // Can contain any information desired. (otherText)
                             i18n("Some text..."),
                             // The program homepage string. (homePageAddress = QString())
                             QStringLiteral("http://example.com/"),
                             // The bug report email address
                             // (bugsEmailAddress = QLatin1String("[email protected]")
                             QStringLiteral("[email protected]"));
        
        aboutData.addAuthor(i18n("Name"), i18n("Task"), QStringLiteral("[email protected]"),
                            QStringLiteral("http://your.website.com"), QStringLiteral("OSC Username"));
        
        KAboutData::setApplicationData(aboutData);
     
        QCommandLineParser parser;
        parser.addHelpOption();
        parser.addVersionOption();
        parser.addPositionalArgument(QStringLiteral("file"), i18n("Document to open"));
        
        aboutData.setupCommandLine(&parser);
        parser.process(app);
        
        aboutData.processCommandLine(&parser);
        
        MainWindow* window = new MainWindow();
        window->show();
        
        if (parser.positionalArguments().count() > 0)
        {
            window->openFile(QUrl::fromUserInput(parser.positionalArguments().at(0), QDir::currentPath()));
        }
        
        return app.exec();
    }
    

    mainwindow.h

    #ifndef MAINWINDOW_H
    #define MAINWINDOW_H
     
    #include <KXmlGuiWindow>
    
    class KTextEdit;
    class KJob;
     
    class MainWindow : public KXmlGuiWindow
    {
        Q_OBJECT
        
      public:
        MainWindow(QWidget *parent=0);
        void openFile(const QUrl &inputFileName);
     
      private:
        KTextEdit* textArea;
        void setupActions();
        
        QString fileName;
     
      private slots:
        void newFile();
        void openFile();
        void saveFile();
        void saveFileAs();
        void saveFileAs(const QString &outputFileName);
        
        void downloadFinished(KJob* job);
    };
     
    #endif
    

    mainwindow.cpp

    #include <QApplication>
    #include <QAction>
    #include <QSaveFile>
    #include <QFileDialog>
    #include <QTextStream>
    #include <QByteArray>
    
    #include <KTextEdit>
    #include <KLocalizedString>
    #include <KActionCollection>
    #include <KStandardAction>
    #include <KMessageBox>
    #include <KIO/Job>
    
    #include "mainwindow.h"
    
    MainWindow::MainWindow(QWidget *parent) : KXmlGuiWindow(parent), fileName(QString())
    {
      textArea = new KTextEdit();
      setCentralWidget(textArea);
      
      setupActions();
    }
    
    void MainWindow::setupActions()
    {
        QAction* clearAction = new QAction(this);
        clearAction->setText(i18n("&Clear"));
        clearAction->setIcon(QIcon::fromTheme("document-new"));
        actionCollection()->setDefaultShortcut(clearAction, Qt::CTRL + Qt::Key_W);
        actionCollection()->addAction("clear", clearAction);
        connect(clearAction, SIGNAL(triggered(bool)), textArea, SLOT(clear()));
        
        KStandardAction::quit(qApp, SLOT(quit()), actionCollection());
        
        KStandardAction::open(this, SLOT(openFile()), actionCollection());
     
        KStandardAction::save(this, SLOT(saveFile()), actionCollection());
     
        KStandardAction::saveAs(this, SLOT(saveFileAs()), actionCollection());
     
        KStandardAction::openNew(this, SLOT(newFile()), actionCollection());
        
        setupGUI(Default, "tutorial5ui.rc");
    }
    
    void MainWindow::newFile()
    {
        fileName.clear();
        textArea->clear();
    }
    
    void MainWindow::saveFileAs(const QString &outputFileName)
    {
        if (!outputFileName.isNull())
        {
            QSaveFile file(outputFileName);
            file.open(QIODevice::WriteOnly);
            
            QByteArray outputByteArray;
            outputByteArray.append(textArea->toPlainText().toUtf8());
            file.write(outputByteArray);
            file.commit();
    
            fileName = outputFileName;
        }
    }
    
    void MainWindow::saveFileAs()
    {
        saveFileAs(QFileDialog::getSaveFileName(this, i18n("Save File As")));
    }
    
    void MainWindow::saveFile()
    {
        if (!fileName.isEmpty())
        {
            saveFileAs(fileName);
        }
        else
        {
            saveFileAs();
        }
    }
    
    
    void MainWindow::openFile()
    {
        openFile(QFileDialog::getOpenFileUrl(this, i18n("Open File")));
    }
        
    void MainWindow::openFile(const QUrl &inputFileName)
    {
        if (!inputFileName.isEmpty())
        {
            KIO::Job* job = KIO::storedGet(inputFileName);
            fileName = inputFileName.toLocalFile();
    
            connect(job, SIGNAL(result(KJob*)), this, SLOT(downloadFinished(KJob*)));
            
            job->exec();
        }
    }
    
    void MainWindow::downloadFinished(KJob* job)
    {
        if (job->error())
        {
            KMessageBox::error(this, job->errorString());
            fileName.clear();
            return;
        }
        
        KIO::StoredTransferJob* storedJob = (KIO::StoredTransferJob*)job;
        textArea->setPlainText(QTextStream(storedJob->data(), QIODevice::ReadOnly).readAll());
    }
    

    tutorial5ui.rc

    <?xml version="1.0" encoding="UTF-8"?>
    <gui name="tutorial5"
         version="1"
         xmlns="http://www.kde.org/standards/kxmlgui/1.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://www.kde.org/standards/kxmlgui/1.0
                             http://www.kde.org/standards/kxmlgui/1.0/kxmlgui.xsd" >
     
      <MenuBar>
        <Menu name="file" >
          <Action name="clear" />
        </Menu>
      </MenuBar>
     
      <ToolBar name="mainToolBar" >
        <text>Main Toolbar</text>
        <Action name="clear" />
      </ToolBar>
     
    </gui>
    

    Explanation

    mainwindow.h

    Here we have done nothing but add a new openFile function which takes a QUrl. Again, we use a QUrl instead of a QString so that we can also work with remote files as if they were local.

    void openFile(const QUrl &inputFileName);
    

    mainwindow.cpp

    There's no new code here, only rearranging. Everything from void openFile() has been moved into void openFile(const QUrl &inputFileName) except the call to QFileDialog::getOpenFileUrl().

    This way, we can call openFile() if we want to display a dialog, or we can call openFile(QString) if we know the name of the file already. Which will be the case when we feed the file name through the command line.

    main.cpp

    This is where all the QCommandLineParser magic happens. In previous examples, we only used the class to feed QApplication the necessary data for using flags like --version or --author. Now we actually get to use it to process command line arguments.

    First, we tell QCommandLineParser that we want to add a new positional arguments. In a nutshell, these are arguments that are not options. -h or --version are options, file is an argument.

    parser.addPositionalArgument(QStringLiteral("file"), i18n("Document to open"));
    


    Later on, we start processing positional arguments, but only if there is one. Otherwise, we proceed as usual. In our case we can only open one file at a time, so only the first file is of interest to us. We call the openFile() function and feed it the URL of the file we want to open, whether it is a local file like $HOME/foo or a remote one like ftp.mydomain.com/bar. We use the overloaded form of QUrl::fromUserInput() in order to set the current path. This is needed in order to work with relative paths like "../baz".

    if (parser.positionalArguments().count() > 0)
    {
        window->openFile(QUrl::fromUserInput(parser.positionalArguments().at(0), QDir::currentPath()));
    }
    

    Make, Install and Run

    CMakeLists.txt

    project (tutorial5)
    
    cmake_minimum_required(VERSION 2.8.12 FATAL_ERROR)
    set(QT_MIN_VERSION "5.3.0")
    set(KF5_MIN_VERSION "5.2.0")
    
    find_package(ECM 1.0.0 REQUIRED NO_MODULE)
    set(CMAKE_MODULE_PATH ${ECM_MODULE_PATH} ${CMAKE_CURRENT_SOURCE_DIR}/cmake)
    
    include(KDEInstallDirs)
    include(KDECMakeSettings)
    include(KDECompilerSettings)
    include(FeatureSummary)
    
    find_package(Qt5 ${QT_MIN_VERSION} CONFIG REQUIRED COMPONENTS 
        Core    # QCommandLineParser, QStringLiteral, QSaveFile, QTextStream, QByteArray
        Widgets # QApplication, QAction, QFileDialog
    )
    
    find_package(KF5 ${KF5_MIN_VERSION} REQUIRED COMPONENTS
        CoreAddons      # KAboutData
        I18n            # KLocalizedString
        XmlGui          # KXmlGuiWindow, KActionCollection
        TextWidgets     # KTextEdit
        ConfigWidgets   # KStandardActions
        WidgetsAddons   # KMessageBox
        KIO             # KIO
    )
        
    feature_summary(WHAT ALL INCLUDE_QUIET_PACKAGES FATAL_ON_MISSING_REQUIRED_PACKAGES)
        
    set(tutorial5_SRCS main.cpp mainwindow.cpp)
    
    add_executable(tutorial5 ${tutorial5_SRCS})
    
    target_link_libraries(tutorial5
        Qt5::Widgets
        KF5::CoreAddons
        KF5::I18n
        KF5::XmlGui
        KF5::TextWidgets
        KF5::ConfigWidgets
        KF5::WidgetsAddons
        KF5::KIOCore
    )
    
    install(TARGETS tutorial5  ${INSTALL_TARGETS_DEFAULT_ARGS})
    
    install(FILES tutorial5ui.rc DESTINATION ${KXMLGUI_INSTALL_DIR}/tutorial5)
    


    With this file, the tutorial can built and run in the same way as tutorial 3 and 4. For more information, see tutorial 3.

    mkdir build && cd build
    cmake .. -DCMAKE_INSTALL_PREFIX=$HOME
    make install
    XDG_DATA_DIRS=$HOME/share:$XDG_DATA_DIRS $HOME/bin/tutorial5
    


    The source code on this page applies only the current KDE Frameworks 5 ("KF5") version. For the older KDE Development Platform ("KDE4"), See Development/Tutorials/First_program/KDE4