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Breadcrumbs go here --> <li>Qt Declarative UI Runtime</li> </ul> </div> <div class="toolbuttons toolblock"> <ul> <li id="smallA" class="t_button">A</li> <li id="medA" class="t_button active">A</li> <li id="bigA" class="t_button">A</li> <li id="print" class="t_button"><a href="javascript:this.print();"> <span>Print</span></a></li> </ul> </div> </div> <div class="content mainContent"> <div class="toc"> <h3><a name="toc">Contents</a></h3> <ul> <li class="level1"><a href="#deploying-qml-based-applications">Deploying QML-based applications</a></li> <li class="level2"><a href="#deploying-with-qdeclarativeview">Deploying with QDeclarativeView</a></li> <li class="level2"><a href="#creating-a-qdeclarativeengine-directly">Creating a QDeclarativeEngine directly</a></li> <li class="level1"><a href="#developing-and-prototyping-with-qml-viewer">Developing and prototyping with QML Viewer</a></li> </ul> </div> <h1 class="title">Qt Declarative UI Runtime</h1> <span class="subtitle"></span> <!-- $$$qmlruntime.html-description --> <div class="descr"> <a name="details"></a> <p>QML documents are loaded and executed by the QML runtime. This includes the Declarative UI engine along with the built-in QML elements and plugin modules, and it also provides access to third-party QML elements and modules.</p> <p>Applications that use QML need to invoke the QML runtime in order to execute QML documents. This can be done by creating a <a href="qdeclarativeview.html">QDeclarativeView</a> or a <a href="qdeclarativeengine.html">QDeclarativeEngine</a>, as described below. In addition, the Declarative UI package includes the <i>Qt QML Viewer</i> tool, which loads <tt>.qml</tt> files. This tool is useful for developing and testing QML code without the need to write a C++ application to load the QML runtime.</p> <a name="deploying-qml-based-applications"></a> <h2>Deploying QML-based applications</h2> <p>To deploy an application that uses QML, the QML runtime must be invoked by the application. This is done by writing a Qt C++ application that loads the <a href="qdeclarativeengine.html">QDeclarativeEngine</a> by either:</p> <ul> <li>Loading the QML file through a <a href="qdeclarativeview.html">QDeclarativeView</a> instance, or</li> <li>Creating a <a href="qdeclarativeengine.html">QDeclarativeEngine</a> instance and loading QML files with <a href="qdeclarativecomponent.html">QDeclarativeComponent</a></li> </ul> <a name="deploying-with-qdeclarativeview"></a> <h3>Deploying with QDeclarativeView</h3> <p><a href="qdeclarativeview.html">QDeclarativeView</a> is a <a href="qwidget.html">QWidget</a>-based class that is able to load QML files. For example, if there is a QML file, <tt>application.qml</tt>, like this:</p> <pre class="qml"> import QtQuick 1.0 <span class="type"><a href="qml-rectangle.html">Rectangle</a></span> { <span class="name">width</span>: <span class="number">100</span>; <span class="name">height</span>: <span class="number">100</span>; <span class="name">color</span>: <span class="string">"red"</span> }</pre> <p>It can be loaded in a Qt application's <tt>main.cpp</tt> file like this:</p> <pre class="cpp"> <span class="preprocessor">#include <QApplication></span> <span class="preprocessor">#include <QDeclarativeView></span> <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); <span class="type"><a href="qdeclarativeview.html">QDeclarativeView</a></span> view; view<span class="operator">.</span>setSource(<span class="type"><a href="qurl.html">QUrl</a></span><span class="operator">::</span>fromLocalFile(<span class="string">"application.qml"</span>)); view<span class="operator">.</span>show(); <span class="keyword">return</span> app<span class="operator">.</span>exec(); }</pre> <p>This creates a <a href="qwidget.html">QWidget</a>-based view that displays the contents of <tt>application.qml</tt>.</p> <p>The application's <tt>.pro</tt> <a href="qmake-project-files.html">project file</a> must specify the <tt>declarative</tt> module for the <tt>QT</tt> variable. For example:</p> <pre class="cpp"> TEMPLATE <span class="operator">+</span><span class="operator">=</span> app QT <span class="operator">+</span><span class="operator">=</span> gui declarative SOURCES <span class="operator">+</span><span class="operator">=</span> main<span class="operator">.</span>cpp</pre> <a name="creating-a-qdeclarativeengine-directly"></a> <h3>Creating a QDeclarativeEngine directly</h3> <p>If <tt>application.qml</tt> does not have any graphical components, or if it is preferred to avoid <a href="qdeclarativeview.html">QDeclarativeView</a> for other reasons, the <a href="qdeclarativeengine.html">QDeclarativeEngine</a> can be constructed directly instead. In this case, <tt>application.qml</tt> is loaded as a <a href="qdeclarativecomponent.html">QDeclarativeComponent</a> instance rather than placed into a view:</p> <pre class="cpp"> <span class="preprocessor">#include <QApplication></span> <span class="preprocessor">#include <QDeclarativeEngine></span> <span class="preprocessor">#include <QDeclarativeContext></span> <span class="preprocessor">#include <QDeclarativeComponent></span> <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); <span class="type"><a href="qdeclarativeengine.html">QDeclarativeEngine</a></span> engine; <span class="type"><a href="qdeclarativecontext.html">QDeclarativeContext</a></span> <span class="operator">*</span>objectContext <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="qdeclarativecontext.html">QDeclarativeContext</a></span>(engine<span class="operator">.</span>rootContext()); <span class="type"><a href="qdeclarativecomponent.html">QDeclarativeComponent</a></span> component(<span class="operator">&</span>engine<span class="operator">,</span> <span class="string">"application.qml"</span>); <span class="type"><a href="qobject.html">QObject</a></span> <span class="operator">*</span>object <span class="operator">=</span> component<span class="operator">.</span>create(objectContext); <span class="comment">// ... delete object and objectContext when necessary</span> <span class="keyword">return</span> app<span class="operator">.</span>exec(); }</pre> <p>See <a href="qtbinding.html">Using QML Bindings in C++ Applications</a> for more information about using <a href="qdeclarativeengine.html">QDeclarativeEngine</a>, <a href="qdeclarativecontext.html">QDeclarativeContext</a> and <a href="qdeclarativecomponent.html">QDeclarativeComponent</a>, as well as details on including QML files through <a href="resources.html">Qt's Resource system</a>.</p> <a name="developing-and-prototyping-with-qml-viewer"></a> <h2>Developing and prototyping with QML Viewer</h2> <p>The Declarative UI package includes a QML runtime tool, the <i>Qt QML Viewer</i>, which loads and displays QML documents. This is useful during the application development phase for prototyping QML-based applications without writing your own C++ applications to invoke the QML runtime.</p> <p>See the <a href="qmlviewer.html">QML Viewer</a> documentation for more details.</p> </div> <!-- @@@qmlruntime.html --> </div> </div> </div> <div class="ft"> <span></span> </div> </div> <div class="footer"> <p> <acronym title="Copyright">©</acronym> 2013 Digia Plc and/or its subsidiaries. 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