Viadeo Twitter Google Bookmarks ! Facebook Digg del.icio.us MySpace Yahoo MyWeb Blinklist Netvouz Reddit Simpy StumbleUpon Bookmarks Windows Live Favorites 
Logo Documentation Qt ·  Page d'accueil  ·  Toutes les classes  ·  Toutes les fonctions  ·  Vues d'ensemble  · 

QXmlStream Bookmarks Example

Files:

The QXmlStream Bookmarks example provides a reader for XML Bookmark Exchange Language (XBEL) files using Qt's QXmlStreamReader class for reading, and QXmlStreamWriter class for writing the files.

XbelWriter Class Definition

The XbelWriter class contains a private instance of QXmlStreamWriter, which provides an XML writer with a streaming API. XbelWriter also has a reference to the QTreeWidget instance where the bookmark hierarchy is stored.

 class XbelWriter
 {
 public:
     XbelWriter(QTreeWidget *treeWidget);
     bool writeFile(QIODevice *device);

 private:
     void writeItem(QTreeWidgetItem *item);
     QXmlStreamWriter xml;
     QTreeWidget *treeWidget;
 };

XbelWriter Class Implementation

The XbelWriter constructor accepts a treeWidget to initialize within its definition. We enable QXmlStreamWriter's auto-formatting property to ensure line-breaks and indentations are added automatically to empty sections between elements, increasing readability as the data is split into several lines.

 XbelWriter::XbelWriter(QTreeWidget *treeWidget)
     : treeWidget(treeWidget)
 {
     xml.setAutoFormatting(true);
 }

The writeFile() function accepts a QIODevice object and sets it using setDevice(). This function then writes the document type definition(DTD), the start element, the version, and treeWidget's top-level items.

 bool XbelWriter::writeFile(QIODevice *device)
 {
     xml.setDevice(device);

     xml.writeStartDocument();
     xml.writeDTD("<!DOCTYPE xbel>");
     xml.writeStartElement("xbel");
     xml.writeAttribute("version", "1.0");
     for (int i = 0; i < treeWidget->topLevelItemCount(); ++i)
         writeItem(treeWidget->topLevelItem(i));

     xml.writeEndDocument();
     return true;
 }

The writeItem() function accepts a QTreeWidgetItem object and writes it to the stream, depending on its tagName, which can either be a "folder", "bookmark", or "separator".

 void XbelWriter::writeItem(QTreeWidgetItem *item)
 {
     QString tagName = item->data(0, Qt::UserRole).toString();
     if (tagName == "folder") {
         bool folded = !treeWidget->isItemExpanded(item);
         xml.writeStartElement(tagName);
         xml.writeAttribute("folded", folded ? "yes" : "no");
         xml.writeTextElement("title", item->text(0));
         for (int i = 0; i < item->childCount(); ++i)
             writeItem(item->child(i));
         xml.writeEndElement();
     } else if (tagName == "bookmark") {
         xml.writeStartElement(tagName);
         if (!item->text(1).isEmpty())
             xml.writeAttribute("href", item->text(1));
         xml.writeTextElement("title", item->text(0));
         xml.writeEndElement();
     } else if (tagName == "separator") {
         xml.writeEmptyElement(tagName);
     }
 }

XbelReader Class Definition

The XbelReader contains a private instance of QXmlStreamReader, the companion class to QXmlStreamWriter. XbelReader also contains a reference to the QTreeWidget that is used to group the bookmarks according to their hierarchy.

 class XbelReader
 {
 public:
     XbelReader(QTreeWidget *treeWidget);

     bool read(QIODevice *device);

     QString errorString() const;

 private:
     void readXBEL();
     void readTitle(QTreeWidgetItem *item);
     void readSeparator(QTreeWidgetItem *item);
     void readFolder(QTreeWidgetItem *item);
     void readBookmark(QTreeWidgetItem *item);

     QTreeWidgetItem *createChildItem(QTreeWidgetItem *item);

     QXmlStreamReader xml;
     QTreeWidget *treeWidget;

     QIcon folderIcon;
     QIcon bookmarkIcon;
 };

XbelReader Class Implementation

The XbelReader constructor accepts a QTreeWidget to initialize the treeWidget within its definition. A QStyle object is used to set treeWidget's style property. The folderIcon is set to QIcon::Normal mode where the pixmap is only displayed when the user is not interacting with the icon. The QStyle::SP_DirClosedIcon, QStyle::SP_DirOpenIcon, and QStyle::SP_FileIcon correspond to standard pixmaps that follow the style of your GUI.

 XbelReader::XbelReader(QTreeWidget *treeWidget)
     : treeWidget(treeWidget)
 {
     QStyle *style = treeWidget->style();

     folderIcon.addPixmap(style->standardPixmap(QStyle::SP_DirClosedIcon),
                          QIcon::Normal, QIcon::Off);
     folderIcon.addPixmap(style->standardPixmap(QStyle::SP_DirOpenIcon),
                          QIcon::Normal, QIcon::On);
     bookmarkIcon.addPixmap(style->standardPixmap(QStyle::SP_FileIcon));
 }

The read() function accepts a QIODevice and sets it using setDevice(). The actual process of reading only takes place if the file is a valid XBEL 1.0 file. Note that the XML input needs to be well-formed to be accepted by QXmlStreamReader. Otherwise, the raiseError() function is used to display an error message. Since the XBEL reader is only concerned with reading XML elements, it makes extensive use of the readNextStartElement() convenience function.

 bool XbelReader::read(QIODevice *device)
 {
     xml.setDevice(device);

     if (xml.readNextStartElement()) {
         if (xml.name() == "xbel" && xml.attributes().value("version") == "1.0")
             readXBEL();
         else
             xml.raiseError(QObject::tr("The file is not an XBEL version 1.0 file."));
     }

     return !xml.error();
 }

The errorString() function is used if an error occurred, in order to obtain a description of the error complete with line and column number information.

 QString XbelReader::errorString() const
 {
     return QObject::tr("%1\nLine %2, column %3")
             .arg(xml.errorString())
             .arg(xml.lineNumber())
             .arg(xml.columnNumber());
 }

The readXBEL() function reads the name of a startElement and calls the appropriate function to read it, depending on whether if its a "folder", "bookmark" or "separator". Otherwise, it calls skipCurrentElement(). The Q_ASSERT() macro is used to provide a pre-condition for the function.

 void XbelReader::readXBEL()
 {
     Q_ASSERT(xml.isStartElement() && xml.name() == "xbel");

     while (xml.readNextStartElement()) {
         if (xml.name() == "folder")
             readFolder(0);
         else if (xml.name() == "bookmark")
             readBookmark(0);
         else if (xml.name() == "separator")
             readSeparator(0);
         else
             xml.skipCurrentElement();
     }
 }

The readTitle() function reads the bookmark's title.

 void XbelReader::readTitle(QTreeWidgetItem *item)
 {
     Q_ASSERT(xml.isStartElement() && xml.name() == "title");

     QString title = xml.readElementText();
     item->setText(0, title);
 }

The readSeparator() function creates a separator and sets its flags. The text is set to 30 "0xB7", the HEX equivalent for period. The element is then skipped using skipCurrentElement().

 void XbelReader::readSeparator(QTreeWidgetItem *item)
 {
     Q_ASSERT(xml.isStartElement() && xml.name() == "separator");

     QTreeWidgetItem *separator = createChildItem(item);
     separator->setFlags(item->flags() & ~Qt::ItemIsSelectable);
     separator->setText(0, QString(30, 0xB7));
     xml.skipCurrentElement();
 }

MainWindow Class Definition

The MainWindow class is a subclass of QMainWindow, with a File menu and a Help menu.

 class MainWindow : public QMainWindow
 {
     Q_OBJECT

 public:
     MainWindow();

 public slots:
     void open();
     void saveAs();
     void about();

 private:
     void createActions();
     void createMenus();

     QTreeWidget *treeWidget;

     QMenu *fileMenu;
     QMenu *helpMenu;
     QAction *openAct;
     QAction *saveAsAct;
     QAction *exitAct;
     QAction *aboutAct;
     QAction *aboutQtAct;
 };

MainWindow Class Implementation

The MainWindow constructor instantiates the QTreeWidget object, treeWidget and sets its header with a QStringList object, labels. The constructor also invokes createActions() and createMenus() to set up the menus and their corresponding actions. The statusBar() is used to display the message "Ready" and the window's size is fixed to 480x320 pixels.

 MainWindow::MainWindow()
 {
     QStringList labels;
     labels << tr("Title") << tr("Location");

     treeWidget = new QTreeWidget;
     treeWidget->header()->setResizeMode(QHeaderView::Stretch);
     treeWidget->setHeaderLabels(labels);
     setCentralWidget(treeWidget);

     createActions();
     createMenus();

     statusBar()->showMessage(tr("Ready"));

     setWindowTitle(tr("QXmlStream Bookmarks"));
     resize(480, 320);
 }

The open() function enables the user to open an XBEL file using QFileDialog::getOpenFileName(). A warning message is displayed along with the fileName and errorString if the file cannot be read or if there is a parse error.

 void MainWindow::open()
 {
     QString fileName =
             QFileDialog::getOpenFileName(this, tr("Open Bookmark File"),
                                          QDir::currentPath(),
                                          tr("XBEL Files (*.xbel *.xml)"));
     if (fileName.isEmpty())
         return;

     treeWidget->clear();

     QFile file(fileName);
     if (!file.open(QFile::ReadOnly | QFile::Text)) {
         QMessageBox::warning(this, tr("QXmlStream Bookmarks"),
                              tr("Cannot read file %1:\n%2.")
                              .arg(fileName)
                              .arg(file.errorString()));
         return;
     }

     XbelReader reader(treeWidget);
     if (!reader.read(&file)) {
         QMessageBox::warning(this, tr("QXmlStream Bookmarks"),
                              tr("Parse error in file %1:\n\n%2")
                              .arg(fileName)
                              .arg(reader.errorString()));
     } else {
         statusBar()->showMessage(tr("File loaded"), 2000);
     }

 }

The saveAs() function displays a QFileDialog, prompting the user for a fileName using QFileDialog::getSaveFileName(). Similar to the open() function, this function also displays a warning message if the file cannot be written to.

 void MainWindow::saveAs()
 {
     QString fileName =
             QFileDialog::getSaveFileName(this, tr("Save Bookmark File"),
                                          QDir::currentPath(),
                                          tr("XBEL Files (*.xbel *.xml)"));
     if (fileName.isEmpty())
         return;

     QFile file(fileName);
     if (!file.open(QFile::WriteOnly | QFile::Text)) {
         QMessageBox::warning(this, tr("QXmlStream Bookmarks"),
                              tr("Cannot write file %1:\n%2.")
                              .arg(fileName)
                              .arg(file.errorString()));
         return;
     }

     XbelWriter writer(treeWidget);
     if (writer.writeFile(&file))
         statusBar()->showMessage(tr("File saved"), 2000);
 }

The about() function displays a QMessageBox with a brief description of the example.

 void MainWindow::about()
 {
    QMessageBox::about(this, tr("About QXmlStream Bookmarks"),
             tr("The <b>QXmlStream Bookmarks</b> example demonstrates how to use Qt's "
                "QXmlStream classes to read and write XML documents."));
 }

In order to implement the open(), saveAs(), exit(), about() and aboutQt() functions, we connect them to QAction objects and add them to the fileMenu and helpMenu. The connections are as shown below:

 void MainWindow::createActions()
 {
     openAct = new QAction(tr("&Open..."), this);
     openAct->setShortcuts(QKeySequence::Open);
     connect(openAct, SIGNAL(triggered()), this, SLOT(open()));

     saveAsAct = new QAction(tr("&Save As..."), this);
     saveAsAct->setShortcuts(QKeySequence::SaveAs);
     connect(saveAsAct, SIGNAL(triggered()), this, SLOT(saveAs()));

     exitAct = new QAction(tr("E&xit"), this);
     exitAct->setShortcuts(QKeySequence::Quit);
     connect(exitAct, SIGNAL(triggered()), this, SLOT(close()));

     aboutAct = new QAction(tr("&About"), this);
     connect(aboutAct, SIGNAL(triggered()), this, SLOT(about()));

     aboutQtAct = new QAction(tr("About &Qt"), this);
     connect(aboutQtAct, SIGNAL(triggered()), qApp, SLOT(aboutQt()));
 }

The createMenus() function creates the fileMenu and helpMenu and adds the QAction objects to them in order to create the menu shown in the screenshot below:

 void MainWindow::createMenus()
 {
     fileMenu = menuBar()->addMenu(tr("&File"));
     fileMenu->addAction(openAct);
     fileMenu->addAction(saveAsAct);
     fileMenu->addAction(exitAct);

     menuBar()->addSeparator();

     helpMenu = menuBar()->addMenu(tr("&Help"));
     helpMenu->addAction(aboutAct);
     helpMenu->addAction(aboutQtAct);
 }

main() Function

The main() function instantiates MainWindow and invokes the show() function.

 int main(int argc, char *argv[])
 {
     QApplication app(argc, argv);
     MainWindow mainWin;
     mainWin.show();
     mainWin.open();
     return app.exec();
 }

See the XML Bookmark Exchange Language Resource Page for more information about XBEL files.

Publicité

Best Of

Actualités les plus lues

Semaine
Mois
Année
  1. « Quelque chose ne va vraiment pas avec les développeurs "modernes" », un développeur à "l'ancienne" critique la multiplication des bibliothèques 72
  2. Apercevoir la troisième dimension ou l'utilisation multithreadée d'OpenGL dans Qt, un article des Qt Quarterly traduit par Guillaume Belz 0
  3. Les développeurs ignorent-ils trop les failles découvertes dans leur code ? Prenez-vous en compte les remarques des autres ? 17
  4. BlackBerry 10 : premières images du prochain OS de RIM qui devrait intégrer des widgets et des tuiles inspirées de Windows Phone 0
  5. Quelles nouveautés de C++11 Visual C++ doit-il rapidement intégrer ? Donnez-nous votre avis 10
  6. Adieu qmake, bienvenue qbs : Qt Building Suite, un outil déclaratif et extensible pour la compilation de projets Qt 17
  7. La rubrique PyQt/PySide a besoin de vous ! 0
Page suivante

Le Qt Developer Network au hasard

Logo

Comment créer une fenêtre À propos

Le Qt Developer Network est un réseau de développeurs Qt anglophone, où ils peuvent partager leur expérience sur le framework. Lire l'article.

Communauté

Ressources

Liens utiles

Contact

  • Vous souhaitez rejoindre la rédaction ou proposer un tutoriel, une traduction, une question... ? Postez dans le forum Contribuez ou contactez-nous par MP ou par email (voir en bas de page).

Qt dans le magazine

Cette page est une traduction d'une page de la documentation de Qt, écrite par Nokia Corporation and/or its subsidiary(-ies). Les éventuels problèmes résultant d'une mauvaise traduction ne sont pas imputables à Nokia. Qt 4.6
Copyright © 2012 Developpez LLC. Tous droits réservés Developpez LLC. Aucune reproduction, même partielle, ne peut être faite de ce site et de l'ensemble de son contenu : textes, documents et images sans l'autorisation expresse de Developpez LLC. Sinon, vous encourez selon la loi jusqu'à 3 ans de prison et jusqu'à 300 000 E de dommages et intérêts. Cette page est déposée à la SACD.
Vous avez déniché une erreur ? Un bug ? Une redirection cassée ? Ou tout autre problème, quel qu'il soit ? Ou bien vous désirez participer à ce projet de traduction ? N'hésitez pas à nous contacter ou par MP !
 
 
 
 
Partenaires

Hébergement Web