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<td >Qt 5.12</td><td ><a href="qtscxml-index.html">Qt SCXML</a></td><td ><a href="examples-qtscxml.html">Qt SCXML Examples</a></td><td >Qt SCXML Media Player Example (Static)</td></tr></table><table class="buildversion"><tr>
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<h3><a name="toc">Contents</a></h3>
<ul>
<li class="level1"><a href="#running-the-example">Running the Example</a></li>
<li class="level1"><a href="#using-the-ecmascript-data-model">Using the ECMAScript Data Model</a></li>
<li class="level1"><a href="#compiling-the-state-machine">Compiling the State Machine</a></li>
<li class="level1"><a href="#instantiating-the-state-machine">Instantiating the State Machine</a></li>
<li class="level1"><a href="#connecting-to-states">Connecting to States</a></li>
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<h1 class="title">Qt SCXML Media Player Example (Static)</h1>
<span class="subtitle"></span>
<!-- $$$mediaplayer-widgets-static-brief -->
<p>A widget-based application that sends data to and receives it from a compiled ECMAScript data model.</p>
<!-- @@@mediaplayer-widgets-static -->
<!-- $$$mediaplayer-widgets-static-description -->
<div class="descr"> <a name="details"></a>
<p class="centerAlign"><img src="images/mediaplayer.png" alt="" /></p><p><i>Media Player Example (Static)</i> demonstrates how to access data from an ECMAScript data model that is compiled into a C++ class.</p>
<p>The UI is created using Qt Widgets.</p>
<a name="running-the-example"></a>
<h2 id="running-the-example">Running the Example</h2>
<p>To run the example from Qt Creator, open the <b>Welcome</b> mode and select the example from <b>Examples</b>. For more information, visit Building and Running an Example.</p>
<a name="using-the-ecmascript-data-model"></a>
<h2 id="using-the-ecmascript-data-model">Using the ECMAScript Data Model</h2>
<p>We specify the data model as a value of the <i>datamodel</i> attribute of the <code><scxml></code> element in <i>mediaplayer-common/mediaplayer.scxml</i>:</p>
<pre class="cpp">
<scxml
xmlns="http://www.w3.org/2005/07/scxml"
version="1.0"
name="MediaPlayerStateMachine"
initial="stopped"
datamodel="ecmascript"
>
<datamodel>
<data id="media"/>
</datamodel>
</pre>
<a name="compiling-the-state-machine"></a>
<h2 id="compiling-the-state-machine">Compiling the State Machine</h2>
<p>We link against the Qt SCXML module by adding the following line to the <i>.pro</i> file:</p>
<pre class="cpp">
QT += widgets scxml
</pre>
<p>We then specify the state machine to compile:</p>
<pre class="cpp">
STATECHARTS = ../mediaplayer-common/mediaplayer.scxml
</pre>
<p>The Qt SCXML Compiler, <code>qscxmlc</code>, is run automatically to generate <i>statemachine.h</i> and <i>statemachine.cpp</i>, and to add them to the <code>HEADERS</code> and <code>SOURCES</code> variables for compilation.</p>
<a name="instantiating-the-state-machine"></a>
<h2 id="instantiating-the-state-machine">Instantiating the State Machine</h2>
<p>We instantiate the generated <code>MediaPlayerStateMachine</code> class in <i>mediaplayer-widgets-static.cpp</i>:</p>
<pre class="cpp">
<span class="preprocessor">#include "mediaplayer.h"</span>
<span class="preprocessor">#include "../mediaplayer-common/mainwindow.h"</span>
<span class="preprocessor">#include <QApplication></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><span class="operator">*</span>argv)
{
<span class="type">QApplication</span> app(argc<span class="operator">,</span> argv);
MediaPlayerStateMachine machine;
MainWindow mainWindow(<span class="operator">&</span>machine);
</pre>
<a name="connecting-to-states"></a>
<h2 id="connecting-to-states">Connecting to States</h2>
<p>The media player state machine will send out events when users tap a control and when playback starts or stops, as specified in the SCXML file:</p>
<pre class="cpp">
<state id="stopped">
<transition event="tap" cond="isValidMedia()" target="playing"/>
</state>
<state id="playing">
<onentry>
<assign location="media" expr="_event.data.media"/>
<send event="playbackStarted">
<param name="media" expr="media"/>
</send>
</onentry>
<onexit>
<send event="playbackStopped">
<param name="media" expr="media"/>
</send>
</onexit>
<transition event="tap" cond="!isValidMedia() || media === _event.data.media" target="stopped"/>
<transition event="tap" cond="isValidMedia() &amp;&amp; media !== _event.data.media" target="playing"/>
</state>
</pre>
<p>To be notified when a state machine sends out an event, we connect to the corresponding signals:</p>
<pre class="cpp">
stateMachine<span class="operator">-</span><span class="operator">></span>connectToEvent(<span class="string">"playbackStarted"</span><span class="operator">,</span> <span class="keyword">this</span><span class="operator">,</span> <span class="operator">&</span>MainWindow<span class="operator">::</span>started);
stateMachine<span class="operator">-</span><span class="operator">></span>connectToEvent(<span class="string">"playbackStopped"</span><span class="operator">,</span> <span class="keyword">this</span><span class="operator">,</span> <span class="operator">&</span>MainWindow<span class="operator">::</span>stopped);
</pre>
<p>Files:</p>
<ul>
<li><a href="qtscxml-mediaplayer-widgets-static-mediaplayer-widgets-static-cpp.html">mediaplayer-widgets-static/mediaplayer-widgets-static.cpp</a></li>
<li><a href="qtscxml-mediaplayer-widgets-static-mediaplayer-widgets-static-pro.html">mediaplayer-widgets-static/mediaplayer-widgets-static.pro</a></li>
<li><a href="qtscxml-mediaplayer-widgets-static-mediaplayer-cpp.html">mediaplayer-widgets-static/mediaplayer.cpp</a></li>
<li><a href="qtscxml-mediaplayer-widgets-static-mediaplayer-h.html">mediaplayer-widgets-static/mediaplayer.h</a></li>
</ul>
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distrib
>
Mageia
>
7
>
armv7hl
>
media
>
core-updates
>
by-pkgid
>
6ed78e842caa17fd5c94d65d685685e0
>
files
>
149
