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<h3><a name="toc">Contents</a></h3>
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<li class="level1"><a href="#the-user-interface">The User Interface</a></li>
<li class="level1"><a href="#previewer-class-definition">Previewer Class Definition</a></li>
<li class="level1"><a href="#previewer-class-implementation">Previewer Class Implementation</a></li>
<li class="level1"><a href="#mainwindow-class-definition">MainWindow Class Definition</a></li>
<li class="level1"><a href="#mainwindow-class-implementation">MainWindow Class Implementation</a></li>
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<h1 class="title">Previewer Example</h1>
<span class="subtitle"></span>
<!-- $$$webkit/previewer-description -->
<div class="descr"> <a name="details"></a>
<p>Files:</p>
<ul>
<li><a href="webkit-previewer-mainwindow-cpp.html">webkit/previewer/mainwindow.cpp</a></li>
<li><a href="webkit-previewer-mainwindow-h.html">webkit/previewer/mainwindow.h</a></li>
<li><a href="webkit-previewer-previewer-cpp.html">webkit/previewer/previewer.cpp</a></li>
<li><a href="webkit-previewer-previewer-h.html">webkit/previewer/previewer.h</a></li>
<li><a href="webkit-previewer-previewer-ui.html">webkit/previewer/previewer.ui</a></li>
<li><a href="webkit-previewer-previewer-mobiles-ui.html">webkit/previewer/previewer_mobiles.ui</a></li>
<li><a href="webkit-previewer-main-cpp.html">webkit/previewer/main.cpp</a></li>
<li><a href="webkit-previewer-previewer-pro.html">webkit/previewer/previewer.pro</a></li>
</ul>
<p>The Previewer example shows how to use <a href="qtwebkit.html">QtWebKit</a>'s <a href="qwebview.html">QWebView</a> to preview HTML data written in a <a href="qplaintextedit.html">QPlainTextEdit</a>.<p class="centerAlign"><img src="images/previewer-example.png" alt="" /></p><a name="the-user-interface"></a>
<h2>The User Interface</h2>
<p>Before we begin, we create a user interface using <i>Qt Designer</i>. Two <a href="qgroupbox.html">QGroupBox</a> objects - the editor group box and the previewer group box are separated by a <a href="qsplitter.html">QSplitter</a>. In the editor group box, we have a <a href="qplaintextedit.html">QPlainTextEdit</a> object, <tt>plainTextEdit</tt>, and two <a href="qpushbutton.html">QPushButton</a> objects. In the previewer group box, we have a <a href="qwebview.html">QWebView</a> object, <tt>webView</tt>.</p>
<p class="centerAlign"><img src="images/previewer-ui.png" alt="" /></p><a name="previewer-class-definition"></a>
<h2>Previewer Class Definition</h2>
<p>The <tt>Previewer</tt> class is a subclass of both <a href="qwidget.html">QWidget</a> and Ui::Form. We subclass Ui::Form in order to embed the <i>Qt Designer</i> user interface form created earlier. This method of embedding forms is known as the <a href="designer-using-a-ui-file.html#the-multiple-inheritance-approach">multiple inheritance approach</a>.</p>
<p>In our <tt>previewer.h</tt> file, we have a constructor and a slot, <tt>on_previewButton_clicked()</tt>.</p>
<pre class="cpp"> <span class="keyword">class</span> Previewer : <span class="keyword">public</span> <span class="type"><a href="qwidget.html">QWidget</a></span><span class="operator">,</span> <span class="keyword">public</span> Ui<span class="operator">::</span>Form
{
Q_OBJECT
<span class="keyword">public</span>:
Previewer(<span class="type"><a href="qwidget.html">QWidget</a></span> <span class="operator">*</span>parent <span class="operator">=</span> <span class="number">0</span>);
<span class="type">void</span> setBaseUrl(<span class="keyword">const</span> <span class="type"><a href="qurl.html">QUrl</a></span> <span class="operator">&</span>url);
<span class="keyword">public</span> <span class="keyword">slots</span>:
<span class="type">void</span> on_previewButton_clicked();
<span class="keyword">private</span>:
<span class="type"><a href="qurl.html">QUrl</a></span> baseUrl;
};</pre>
<a name="previewer-class-implementation"></a>
<h2>Previewer Class Implementation</h2>
<p>The <tt>Previewer</tt>'s constructor is only responsible for setting up the user interface.</p>
<pre class="cpp"> Previewer<span class="operator">::</span>Previewer(<span class="type"><a href="qwidget.html">QWidget</a></span> <span class="operator">*</span>parent)
: <span class="type"><a href="qwidget.html">QWidget</a></span>(parent)
{
setupUi(<span class="keyword">this</span>);
}</pre>
<p>The <tt>on_previewButton_clicked()</tt> is a slot corresponding to the <tt>previewButton</tt>'s <a href="qabstractbutton.html#clicked">clicked()</a> signal. When the <tt>previewButton</tt> is clicked, we extract the contents of <tt>plainTextEdit</tt>, and then invoke the <a href="qwebview.html#setHtml">setHtml()</a> function to display our contents as HTML.</p>
<pre class="cpp"> <span class="type">void</span> Previewer<span class="operator">::</span>on_previewButton_clicked()
{
<span class="comment">// Update the contents in web viewer</span>
<span class="type"><a href="qstring.html">QString</a></span> text <span class="operator">=</span> plainTextEdit<span class="operator">-</span><span class="operator">></span>toPlainText();
webView<span class="operator">-</span><span class="operator">></span>setHtml(text<span class="operator">,</span> baseUrl);
<span class="comment">// In mobile devices, change the tab</span>
<span class="preprocessor">#if defined Q_OS_SYMBIAN || defined Q_WS_HILDON || defined Q_WS_MAEMO_5 || defined Q_WS_SIMULATOR</span>
tabWidget<span class="operator">-</span><span class="operator">></span>setCurrentWidget(tabHTMLPreview);
<span class="preprocessor">#endif</span>
}</pre>
<a name="mainwindow-class-definition"></a>
<h2>MainWindow Class Definition</h2>
<p>The <tt>MainWindow</tt> class for the Previewer example is a subclass of <a href="qmainwindow.html">QMainWindow</a> with a constructor and five private slots: <tt>open()</tt>, <tt>openUrl()</tt>, <tt>save()</tt>, <tt>about()</tt> and <tt>updateTextEdit()</tt>.</p>
<pre class="cpp"> <span class="keyword">class</span> MainWindow : <span class="keyword">public</span> <span class="type"><a href="qmainwindow.html">QMainWindow</a></span>
{
Q_OBJECT
<span class="keyword">public</span>:
MainWindow();
<span class="keyword">private</span> <span class="keyword">slots</span>:
<span class="type">void</span> open();
<span class="type">void</span> openUrl();
<span class="type">void</span> save();
<span class="type">void</span> about();
<span class="type">void</span> updateTextEdit();</pre>
<p>The private objects in <tt>MainWindow</tt> are <tt>centralWidget</tt>, which is a <tt>Previewer</tt> object, <tt>fileMenu</tt>, <tt>helpMenu</tt> and the <a href="qaction.html">QAction</a> objects <tt>openAct</tt>, <tt>openUrlAct</tt>, <tt>saveAct</tt>, <tt>exitAct</tt>, <tt>aboutAct</tt> and <tt>aboutQtAct</tt>.</p>
<pre class="cpp"> <span class="keyword">private</span>:
Previewer <span class="operator">*</span>centralWidget;
<span class="type"><a href="qmenu.html">QMenu</a></span> <span class="operator">*</span>fileMenu;
<span class="type"><a href="qmenu.html">QMenu</a></span> <span class="operator">*</span>helpMenu;
<span class="type"><a href="qaction.html">QAction</a></span> <span class="operator">*</span>openAct;
<span class="type"><a href="qaction.html">QAction</a></span> <span class="operator">*</span>openUrlAct;
<span class="type"><a href="qaction.html">QAction</a></span> <span class="operator">*</span>saveAct;
<span class="type"><a href="qaction.html">QAction</a></span> <span class="operator">*</span>exitAct;
<span class="type"><a href="qaction.html">QAction</a></span> <span class="operator">*</span>aboutAct;
<span class="type"><a href="qaction.html">QAction</a></span> <span class="operator">*</span>aboutQtAct;
<span class="type">void</span> createActions();
<span class="type">void</span> createMenus();
<span class="type">void</span> setStartupText();
};</pre>
<p>There are three private functions: <tt>createActions()</tt>, <tt>createMenus()</tt> and <tt>setStartupText()</tt>. The <tt>createActions()</tt> and <tt>createMenus()</tt> functions are necessary to set up the main window's actions and assign them to the <b>File</b> and <b>Help</b> menus. The <tt>setStartupText()</tt> function, on the other hand, displays a description about the example in its HTML Previewer window.</p>
<a name="mainwindow-class-implementation"></a>
<h2>MainWindow Class Implementation</h2>
<p>The <tt>MainWindow</tt>'s constructor invokes <tt>createActions()</tt> and <tt>createMenus()</tt> to set up the <b>File</b> menu and <b>Help</b> menu. Then, the <tt>Previewer</tt> object, <tt>centralWidget</tt>, is set to the main window's central widget. Also, we connect <tt>webView</tt>'s <a href="qwebview.html#loadFinished">loadFinished()</a> signal to our <tt>updateTextEdit()</tt> slot. Finally, we call the <tt>setStartupText()</tt> function to display the description of the example.</p>
<pre class="cpp"> MainWindow<span class="operator">::</span>MainWindow()
{
createActions();
createMenus();
centralWidget <span class="operator">=</span> <span class="keyword">new</span> Previewer(<span class="keyword">this</span>);
setCentralWidget(centralWidget);
connect(centralWidget<span class="operator">-</span><span class="operator">></span>webView<span class="operator">,</span> SIGNAL(loadFinished(<span class="type">bool</span>))<span class="operator">,</span>
<span class="keyword">this</span><span class="operator">,</span> SLOT(updateTextEdit()));
setStartupText();
}</pre>
<p>Within the <tt>createActions()</tt> function, we instantiate all our private <a href="qaction.html">QAction</a> objects which we declared in <tt>mainwindow.h</tt>. We set the short cut and status tip for these actions and connect their <a href="qaction.html#triggered">triggered()</a> signal to appropriate slots.</p>
<pre class="cpp"> <span class="type">void</span> MainWindow<span class="operator">::</span>createActions()
{
openAct <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="qaction.html">QAction</a></span>(tr(<span class="string">"&Open..."</span>)<span class="operator">,</span> <span class="keyword">this</span>);
openAct<span class="operator">-</span><span class="operator">></span>setShortcuts(<span class="type"><a href="qkeysequence.html">QKeySequence</a></span><span class="operator">::</span>Open);
openAct<span class="operator">-</span><span class="operator">></span>setStatusTip(tr(<span class="string">"Open an existing HTML file"</span>));
connect(openAct<span class="operator">,</span> SIGNAL(triggered())<span class="operator">,</span> <span class="keyword">this</span><span class="operator">,</span> SLOT(open()));
openUrlAct <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="qaction.html">QAction</a></span>(tr(<span class="string">"&Open URL..."</span>)<span class="operator">,</span> <span class="keyword">this</span>);
openUrlAct<span class="operator">-</span><span class="operator">></span>setShortcut(tr(<span class="string">"Ctrl+U"</span>));
openUrlAct<span class="operator">-</span><span class="operator">></span>setStatusTip(tr(<span class="string">"Open a URL"</span>));
connect(openUrlAct<span class="operator">,</span> SIGNAL(triggered())<span class="operator">,</span> <span class="keyword">this</span><span class="operator">,</span> SLOT(openUrl()));
...</pre>
<p>The <tt>createMenus()</tt> function instantiates the <a href="qmenu.html">QMenu</a> items, <tt>fileMenu</tt> and <tt>helpMenu</tt> and adds them to the main window's <a href="qmainwindow.html#menuBar">menu bar</a>.</p>
<pre class="cpp"> <span class="type">void</span> MainWindow<span class="operator">::</span>createMenus()
{
fileMenu <span class="operator">=</span> menuBar()<span class="operator">-</span><span class="operator">></span>addMenu(tr(<span class="string">"&File"</span>));
fileMenu<span class="operator">-</span><span class="operator">></span>addAction(openAct);
fileMenu<span class="operator">-</span><span class="operator">></span>addAction(openUrlAct);
fileMenu<span class="operator">-</span><span class="operator">></span>addAction(saveAct);
fileMenu<span class="operator">-</span><span class="operator">></span>addSeparator();
fileMenu<span class="operator">-</span><span class="operator">></span>addAction(exitAct);
menuBar()<span class="operator">-</span><span class="operator">></span>addSeparator();
helpMenu <span class="operator">=</span> menuBar()<span class="operator">-</span><span class="operator">></span>addMenu(tr(<span class="string">"&Help"</span>));
helpMenu<span class="operator">-</span><span class="operator">></span>addAction(aboutAct);
helpMenu<span class="operator">-</span><span class="operator">></span>addAction(aboutQtAct);
}</pre>
<p>The example also provides an <tt>about()</tt> slot to describe its purpose.</p>
<pre class="cpp"> <span class="type">void</span> MainWindow<span class="operator">::</span>about()
{
<span class="type"><a href="qmessagebox.html">QMessageBox</a></span><span class="operator">::</span>about(<span class="keyword">this</span><span class="operator">,</span> tr(<span class="string">"About Previewer"</span>)<span class="operator">,</span>
tr(<span class="string">"The <b>Previewer</b> example demonstrates how to "</span>
<span class="string">"view HTML documents using a QWebView."</span>));
}</pre>
<p>The <tt>MainWindow</tt> class provides two types of <b>Open</b> functions: <tt>open()</tt> and <tt>openUrl()</tt>. The <tt>open()</tt> function opens an HTML file with <tt>fileName</tt>, and reads it with <a href="qtextstream.html">QTextStream</a>. The function then displays the output on <tt>plainTextEdit</tt>. The file's name is obtained using <a href="qfiledialog.html">QFileDialog</a>'s <a href="qfiledialog.html#getOpenFileName">getOpenFileName()</a> function.</p>
<pre class="cpp"> <span class="type">void</span> MainWindow<span class="operator">::</span>open()
{
<span class="type"><a href="qstring.html">QString</a></span> fileName <span class="operator">=</span> <span class="type"><a href="qfiledialog.html">QFileDialog</a></span><span class="operator">::</span>getOpenFileName(<span class="keyword">this</span>);
<span class="keyword">if</span> (<span class="operator">!</span>fileName<span class="operator">.</span>isEmpty()) {
<span class="comment">// read from file</span>
<span class="type"><a href="qfile.html">QFile</a></span> file(fileName);
<span class="keyword">if</span> (<span class="operator">!</span>file<span class="operator">.</span>open(<span class="type"><a href="qiodevice.html">QIODevice</a></span><span class="operator">::</span>ReadOnly)) {
<span class="type"><a href="qmessagebox.html">QMessageBox</a></span><span class="operator">::</span>information(<span class="keyword">this</span><span class="operator">,</span> tr(<span class="string">"Unable to open file"</span>)<span class="operator">,</span>
file<span class="operator">.</span>errorString());
<span class="keyword">return</span>;
}
<span class="type"><a href="qtextstream.html">QTextStream</a></span> out(<span class="operator">&</span>file);
<span class="type"><a href="qstring.html">QString</a></span> output <span class="operator">=</span> out<span class="operator">.</span>readAll();
<span class="comment">// display contents</span>
centralWidget<span class="operator">-</span><span class="operator">></span>plainTextEdit<span class="operator">-</span><span class="operator">></span>setPlainText(output);
centralWidget<span class="operator">-</span><span class="operator">></span>setBaseUrl(<span class="type"><a href="qurl.html">QUrl</a></span><span class="operator">::</span>fromLocalFile(fileName));
}
}</pre>
<p>The <tt>openUrl()</tt> function, on the other hand, displays a <a href="qinputdialog.html">QInputDialog</a> to obtain a URL, and displays it on <tt>webView</tt>.</p>
<pre class="cpp"> <span class="type">void</span> MainWindow<span class="operator">::</span>openUrl()
{
<span class="type">bool</span> ok;
<span class="type"><a href="qstring.html">QString</a></span> url <span class="operator">=</span> <span class="type"><a href="qinputdialog.html">QInputDialog</a></span><span class="operator">::</span>getText(<span class="keyword">this</span><span class="operator">,</span> tr(<span class="string">"Enter a URL"</span>)<span class="operator">,</span>
tr(<span class="string">"URL:"</span>)<span class="operator">,</span> <span class="type"><a href="qlineedit.html">QLineEdit</a></span><span class="operator">::</span>Normal<span class="operator">,</span> <span class="string">"http://"</span><span class="operator">,</span> <span class="operator">&</span>ok);
<span class="keyword">if</span> (ok <span class="operator">&</span><span class="operator">&</span> <span class="operator">!</span>url<span class="operator">.</span>isEmpty()) {
centralWidget<span class="operator">-</span><span class="operator">></span>webView<span class="operator">-</span><span class="operator">></span>setUrl(url);
}
}</pre>
<p>In order to save a HTML file, the <tt>save()</tt> function first extracts the contents of <tt>plainTextEdit</tt> and displays a <a href="qfiledialog.html">QFileDialog</a> to obtain <tt>fileName</tt>. Then, we use a <a href="qtextstream.html">QTextStream</a> object, <tt>in</tt>, to write to <tt>file</tt>.</p>
<pre class="cpp"> <span class="type">void</span> MainWindow<span class="operator">::</span>save()
{
<span class="type"><a href="qstring.html">QString</a></span> content <span class="operator">=</span> centralWidget<span class="operator">-</span><span class="operator">></span>plainTextEdit<span class="operator">-</span><span class="operator">></span>toPlainText();
<span class="type"><a href="qstring.html">QString</a></span> fileName <span class="operator">=</span> <span class="type"><a href="qfiledialog.html">QFileDialog</a></span><span class="operator">::</span>getSaveFileName(<span class="keyword">this</span>);
<span class="keyword">if</span> (<span class="operator">!</span>fileName<span class="operator">.</span>isEmpty()) {
<span class="comment">// save to file</span>
<span class="type"><a href="qfile.html">QFile</a></span> file(fileName);
<span class="keyword">if</span> (<span class="operator">!</span>file<span class="operator">.</span>open(<span class="type"><a href="qiodevice.html">QIODevice</a></span><span class="operator">::</span>WriteOnly)) {
<span class="type"><a href="qmessagebox.html">QMessageBox</a></span><span class="operator">::</span>information(<span class="keyword">this</span><span class="operator">,</span> tr(<span class="string">"Unable to open file"</span>)<span class="operator">,</span>
file<span class="operator">.</span>errorString());
<span class="keyword">return</span>;
}
<span class="type"><a href="qtextstream.html">QTextStream</a></span> in(<span class="operator">&</span>file);
in <span class="operator"><</span><span class="operator"><</span> content;
}
}</pre>
<p>Earlier, in <tt>MainWindow</tt>'s constructor, we connected <tt>webView</tt>'s <a href="qwebview.html#loadFinished">loadFinished()</a> signal to our private <tt>updateTextEdit()</tt> slot. This slot updates the contents of <tt>plainTextEdit</tt> with the HTML source of the web page's main frame, obtained using <a href="qwebframe.html">QWebFrame</a>'s <a href="qwebframe.html#toHtml">toHtml()</a> function.</p>
<pre class="cpp"> <span class="type">void</span> MainWindow<span class="operator">::</span>updateTextEdit()
{
<span class="type"><a href="qwebframe.html">QWebFrame</a></span> <span class="operator">*</span>mainFrame <span class="operator">=</span> centralWidget<span class="operator">-</span><span class="operator">></span>webView<span class="operator">-</span><span class="operator">></span>page()<span class="operator">-</span><span class="operator">></span>mainFrame();
<span class="type"><a href="qstring.html">QString</a></span> frameText <span class="operator">=</span> mainFrame<span class="operator">-</span><span class="operator">></span>toHtml();
centralWidget<span class="operator">-</span><span class="operator">></span>plainTextEdit<span class="operator">-</span><span class="operator">></span>setPlainText(frameText);
}</pre>
<p>To provide a description about the Previewer example, when it starts up, we use the <tt>setStartupText()</tt> function, as shown below:</p>
<pre class="cpp"> <span class="type">void</span> MainWindow<span class="operator">::</span>setStartupText()
{
<span class="type"><a href="qstring.html">QString</a></span> string <span class="operator">=</span> <span class="string">"<html><body><h1>HTML Previewer</h1>"</span>
<span class="string">" <p>This example shows you how to use QWebView to"</span>
<span class="string">" preview HTML data written in a QPlainTextEdit.</p>"</span>
<span class="string">" </body></html>"</span>;
centralWidget<span class="operator">-</span><span class="operator">></span>webView<span class="operator">-</span><span class="operator">></span>setHtml(string);
}</pre>
<a name="the-function"></a>
<h2>The <tt>main()</tt> Function</h2>
<p>The <tt>main()</tt> function instantiates a <tt>MainWindow</tt> object, <tt>mainWindow</tt>, and displays it with the <a href="qwidget.html#show">show()</a> function.</p>
<pre class="cpp"> <span class="type">int</span> main(<span class="type">int</span> argc<span class="operator">,</span> <span class="type">char</span> <span class="operator">*</span> argv<span class="operator">[</span><span class="operator">]</span>)
{
<span class="type"><a href="qapplication.html">QApplication</a></span> app(argc<span class="operator">,</span> argv);
MainWindow mainWindow;
<span class="preprocessor">#if defined Q_OS_SYMBIAN || defined Q_WS_HILDON || defined Q_WS_MAEMO_5 || defined Q_WS_SIMULATOR</span>
mainWindow<span class="operator">.</span>showMaximized();
<span class="preprocessor">#else</span>
mainWindow<span class="operator">.</span>show();
<span class="preprocessor">#endif</span>
<span class="keyword">return</span> app<span class="operator">.</span>exec();
}</pre>
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