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<td width="1"> </td><td class="postheader" valign="center"><a href="index.html"><font color="#004faf">Home</font></a> · <a href="classes.html"><font color="#004faf">All Classes</font></a> · <a href="mainclasses.html"><font color="#004faf">Main Classes</font></a> · <a href="groups.html"><font color="#004faf">Grouped Classes</font></a> · <a href="modules.html"><font color="#004faf">Modules</font></a> · <a href="functions.html"><font color="#004faf">Functions</font></a></td>
<td align="right" valign="top" width="230"><a href="http://www.trolltech.com"><img src="images/trolltech-logo.png" align="right" width="203" height="32" border="0" /></a></td></tr></table><h1 align="center">QXmlStream Bookmarks Example<br /><small></small></h1>
<p>Files:</p>
<ul>
<li><a href="xml-streambookmarks-mainwindow-cpp.html">xml/streambookmarks/mainwindow.cpp</a></li>
<li><a href="xml-streambookmarks-mainwindow-h.html">xml/streambookmarks/mainwindow.h</a></li>
<li><a href="xml-streambookmarks-xbelreader-cpp.html">xml/streambookmarks/xbelreader.cpp</a></li>
<li><a href="xml-streambookmarks-xbelreader-h.html">xml/streambookmarks/xbelreader.h</a></li>
<li><a href="xml-streambookmarks-xbelwriter-cpp.html">xml/streambookmarks/xbelwriter.cpp</a></li>
<li><a href="xml-streambookmarks-xbelwriter-h.html">xml/streambookmarks/xbelwriter.h</a></li>
<li><a href="xml-streambookmarks-main-cpp.html">xml/streambookmarks/main.cpp</a></li>
</ul>
<p>The QXmlStream Bookmarks example provides a reader for XML Bookmark Exchange Language (XBEL) files using Qt's <a href="qxmlstreamreader.html">QXmlStreamReader</a> class for reading, and <a href="qxmlstreamwriter.html">QXmlStreamWriter</a> class for writing the files.</p>
<p align="center"><img src="images/xmlstreamexample-screenshot.png" /></p><a name="xbelwriter-class-definition"></a>
<h2>XbelWriter Class Definition</h2>
<p>The <tt>XbelWriter</tt> class is a subclass of <a href="qxmlstreamreader.html">QXmlStreamReader</a>, which provides an XML parser with a streaming API. <tt>XbelWriter</tt> also contains a private instance of <a href="qtreewidget.html">QTreeWidget</a> in order to display the bookmarks according to hierarchies.</p>
<pre> class XbelWriter : public QXmlStreamWriter
{
public:
XbelWriter(QTreeWidget *treeWidget);
bool writeFile(QIODevice *device);
private:
void writeItem(QTreeWidgetItem *item);
QTreeWidget *treeWidget;
};</pre>
<a name="xbelwriter-class-implementation"></a>
<h2>XbelWriter Class Implementation</h2>
<p>The <tt>XbelWriter</tt> constructor accepts a <i>treeWidget</i> to initialize within its definition. We enable <a href="qxmlstreamwriter.html">QXmlStreamWriter</a>'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.</p>
<pre> XbelWriter::XbelWriter(QTreeWidget *treeWidget)
: treeWidget(treeWidget)
{
setAutoFormatting(true);
}</pre>
<p>The <tt>writeFile()</tt> function accepts a <a href="qiodevice.html">QIODevice</a> object and sets it using <tt>setDevice()</tt>. This function then writes the document type definition(DTD), the start element, the version, and <tt>treeWidget</tt>'s top-level items.</p>
<pre> bool XbelWriter::writeFile(QIODevice *device)
{
setDevice(device);
writeStartDocument();
writeDTD("<!DOCTYPE xbel>");
writeStartElement("xbel");
writeAttribute("version", "1.0");
for (int i = 0; i < treeWidget->topLevelItemCount(); ++i)
writeItem(treeWidget->topLevelItem(i));
writeEndDocument();
return true;
}</pre>
<p>The <tt>writeItem()</tt> function accepts a <a href="qtreewidget.html">QTreeWidget</a> object and writes it to the stream, depending on its <tt>tagName</tt>, which can either be a "folder", "bookmark", or "separator".</p>
<pre> void XbelWriter::writeItem(QTreeWidgetItem *item)
{
QString tagName = item->data(0, Qt::UserRole).toString();
if (tagName == "folder") {
bool folded = !treeWidget->isItemExpanded(item);
writeStartElement(tagName);
writeAttribute("folded", folded ? "yes" : "no");
writeTextElement("title", item->text(0));
for (int i = 0; i < item->childCount(); ++i)
writeItem(item->child(i));
writeEndElement();
} else if (tagName == "bookmark") {
writeStartElement(tagName);
if (!item->text(1).isEmpty())
writeAttribute("href", item->text(1));
writeTextElement("title", item->text(0));
writeEndElement();
} else if (tagName == "separator") {
writeEmptyElement(tagName);
}
}</pre>
<a name="xbelreader-class-definition"></a>
<h2>XbelReader Class Definition</h2>
<p>The <tt>XbelReader</tt> class is a subclass of <a href="qxmlstreamreader.html">QXmlStreamReader</a>, the pendent class for <a href="qxmlstreamwriter.html">QXmlStreamWriter</a>. <tt>XbelReader</tt> contains a private instance of <a href="qtreewidget.html">QTreeWidget</a> to group bookmarks according to their hierarchies.</p>
<pre> class XbelReader : public QXmlStreamReader
{
public:
XbelReader(QTreeWidget *treeWidget);
bool read(QIODevice *device);
private:
void readUnknownElement();
void readXBEL();
void readTitle(QTreeWidgetItem *item);
void readSeparator(QTreeWidgetItem *item);
void readFolder(QTreeWidgetItem *item);
void readBookmark(QTreeWidgetItem *item);
QTreeWidgetItem *createChildItem(QTreeWidgetItem *item);
QTreeWidget *treeWidget;
QIcon folderIcon;
QIcon bookmarkIcon;
};</pre>
<a name="xbelreader-class-implementation"></a>
<h2>XbelReader Class Implementation</h2>
<p>The <tt>XbelReader</tt> constructor accepts a <a href="qtreewidget.html">QTreeWidget</a> to initialize the <tt>treeWidget</tt> within its definition. A <a href="qstyle.html">QStyle</a> object is used to set <tt>treeWidget</tt>'s style property. The <tt>folderIcon</tt> is set to <a href="qicon.html#Mode-enum">QIcon::Normal</a> mode where the pixmap is only displayed when the user is not interacting with the icon. The <a href="qstyle.html#StandardPixmap-enum">QStyle::SP_DirClosedIcon</a>, <a href="qstyle.html#StandardPixmap-enum">QStyle::SP_DirOpenIcon</a>, and <a href="qstyle.html#StandardPixmap-enum">QStyle::SP_FileIcon</a> correspond to standard pixmaps that follow the style of your GUI.</p>
<pre> 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));
}</pre>
<p>The <tt>read()</tt> function accepts a <a href="qiodevice.html">QIODevice</a> and sets it using <a href="qxmlstreamreader.html#setDevice">setDevice()</a>. The actual process of reading only takes place in event the file is a valid XBEL 1.0 file. Otherwise, the <a href="qxmlstreamreader.html#raiseError">raiseError()</a> function is used to display an error message.</p>
<pre> bool XbelReader::read(QIODevice *device)
{
setDevice(device);
while (!atEnd()) {
readNext();
if (isStartElement()) {
if (name() == "xbel" && attributes().value("version") == "1.0")
readXBEL();
else
raiseError(QObject::tr("The file is not an XBEL version 1.0 file."));
}
}
return !error();
}</pre>
<p>The <tt>readUnknownElement()</tt> function reads an unknown element. The <a href="qtglobal.html#Q_ASSERT">Q_ASSERT</a>() macro is used to provide a pre-condition for the function.</p>
<pre> void XbelReader::readUnknownElement()
{
Q_ASSERT(isStartElement());
while (!atEnd()) {
readNext();
if (isEndElement())
break;
if (isStartElement())
readUnknownElement();
}
}</pre>
<p>The <tt>readXBEL()</tt> 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 <tt>readUnknownElement()</tt>.</p>
<pre> void XbelReader::readXBEL()
{
Q_ASSERT(isStartElement() && name() == "xbel");
while (!atEnd()) {
readNext();
if (isEndElement())
break;
if (isStartElement()) {
if (name() == "folder")
readFolder(0);
else if (name() == "bookmark")
readBookmark(0);
else if (name() == "separator")
readSeparator(0);
else
readUnknownElement();
}
}
}</pre>
<p>The <tt>readTitle()</tt> function reads the bookmark's title.</p>
<pre> void XbelReader::readTitle(QTreeWidgetItem *item)
{
Q_ASSERT(isStartElement() && name() == "title");
QString title = readElementText();
item->setText(0, title);
}</pre>
<p>The <tt>readSeparator()</tt> function creates a separator and sets its flags. The text is set to 30 "0xB7", the HEX equivalent for period, and then read using <tt>readElementText()</tt>.</p>
<pre> void XbelReader::readSeparator(QTreeWidgetItem *item)
{
QTreeWidgetItem *separator = createChildItem(item);
separator->setFlags(item->flags() & ~Qt::ItemIsSelectable);
separator->setText(0, QString(30, 0xB7));
readElementText();
}</pre>
<a name="mainwindow-class-definition"></a>
<h2>MainWindow Class Definition</h2>
<p>The <tt>MainWindow</tt> class is a subclass of <a href="qmainwindow.html">QMainWindow</a>, with a <tt>File</tt> menu and a <tt>Help</tt> menu.</p>
<pre> class MainWindow : public QMainWindow
{
Q_OBJECT
public:
MainWindow();
private 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;
};</pre>
<a name="mainwindow-class-implementation"></a>
<h2>MainWindow Class Implementation</h2>
<p>The <tt>MainWindow</tt> constructor instantiates the <a href="qtreewidget.html">QTreeWidget</a> object, <tt>treeWidget</tt> and sets its header with a <a href="qstringlist.html">QStringList</a> object, <tt>labels</tt>. The constructor also invokes <tt>createActions()</tt> and <tt>createMenus()</tt> to set up the menus and their corresponding actions. The <tt>statusBar()</tt> is used to display the message "Ready" and the window's size is fixed to 480x320 pixels.</p>
<pre> 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);
}</pre>
<p>The <tt>open()</tt> function enables the user to open an XBEL file using <a href="qfiledialog.html#getOpenFileName">QFileDialog::getOpenFileName</a>(). A warning message is displayed along with the <tt>fileName</tt> and <tt>errorString</tt> if the file cannot be read or if there is a parse error.</p>
<pre> 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 at line %2, column %3:\n%4")
.arg(fileName)
.arg(reader.lineNumber())
.arg(reader.columnNumber())
.arg(reader.errorString()));
} else {
statusBar()->showMessage(tr("File loaded"), 2000);
}
}</pre>
<p>The <tt>saveAs()</tt> function displays a <a href="qfiledialog.html">QFileDialog</a>, prompting the user for a <tt>fileName</tt> using <a href="qfiledialog.html#getSaveFileName">QFileDialog::getSaveFileName</a>(). Similar to the <tt>open()</tt> function, this function also displays a warning message if the file cannot be written to.</p>
<pre> 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);
}</pre>
<p>The <tt>about()</tt> function displays a <a href="qmessagebox.html">QMessageBox</a> with a brief description of the example.</p>
<pre> 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."));
}</pre>
<p>In order to implement the <tt>open()</tt>, <tt>saveAs()</tt>, <tt>exit()</tt>, <tt>about()</tt> and <tt>aboutQt()</tt> functions, we connect them to <a href="qaction.html">QAction</a> objects and add them to the <tt>fileMenu</tt> and <tt>helpMenu</tt>. The connections are as shown below:</p>
<pre> void MainWindow::createActions()
{
openAct = new QAction(tr("&Open..."), this);
openAct->setShortcut(tr("Ctrl+O"));
connect(openAct, SIGNAL(triggered()), this, SLOT(open()));
saveAsAct = new QAction(tr("&Save As..."), this);
saveAsAct->setShortcut(tr("Ctrl+S"));
connect(saveAsAct, SIGNAL(triggered()), this, SLOT(saveAs()));
exitAct = new QAction(tr("E&xit"), this);
exitAct->setShortcut(tr("Ctrl+Q"));
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()));
}</pre>
<p>The <tt>createMenus()</tt> function creates the <tt>fileMenu</tt> and <tt>helpMenu</tt> and adds the <a href="qaction.html">QAction</a> objects to them in order to create the menu shown in the screenshot below:</p>
<p><table align="center" cellpadding="2" cellspacing="1" border="0">
<tr valign="top" class="odd"><td><img src="images/xmlstreamexample-filemenu.png" /></td><td><img src="images/xmlstreamexample-helpmenu.png" /></td></tr>
</table></p>
<pre> 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);
}</pre>
<a name="function"></a>
<h2><tt>main()</tt> Function</h2>
<p>The <tt>main()</tt> function instantiates <tt>MainWindow</tt> and invokes the <tt>show()</tt> function.</p>
<pre> int main(int argc, char *argv[])
{
QApplication app(argc, argv);
MainWindow mainWin;
mainWin.show();
return app.exec();
}</pre>
<p>See the <a href="http://pyxml.sourceforge.net/topics/xbel/">XML Bookmark Exchange Language Resource Page</a> for more information about XBEL files.</p>
<p /><address><hr /><div align="center">
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<td width="30%">Copyright © 2008 <a href="trolltech.html">Trolltech</a></td>
<td width="40%" align="center"><a href="trademarks.html">Trademarks</a></td>
<td width="30%" align="right"><div align="right">Qt 4.3.4</div></td>
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>
Mandriva
>
2008.1
>
x86_64
>
media
>
main-release
>
by-pkgid
>
c5a68a1bfbb41dd7ab32131d8bbca747
>
files
>
4154
