<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE html> <html lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <!-- mediaplayer-widgets-static.qdoc --> <title>Qt SCXML Media Player Example (Static) | Qt SCXML 5.9</title> <link rel="stylesheet" type="text/css" href="style/offline-simple.css" /> <script type="text/javascript"> document.getElementsByTagName("link").item(0).setAttribute("href", "style/offline.css"); // loading style sheet breaks anchors that were jumped to before // so force jumping to anchor again setTimeout(function() { var anchor = location.hash; // need to jump to different anchor first (e.g. none) location.hash = "#"; setTimeout(function() { location.hash = anchor; }, 0); }, 0); </script> </head> <body> <div class="header" id="qtdocheader"> <div class="main"> <div class="main-rounded"> <div class="navigationbar"> <table><tr> <td >Qt 5.9</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> <td id="buildversion" width="100%" align="right">Qt 5.9.4 Reference Documentation</td> </tr></table> </div> </div> <div class="content"> <div class="line"> <div class="content mainContent"> <div class="sidebar"> <div class="toc"> <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> </ul> </div> <div class="sidebar-content" id="sidebar-content"></div></div> <h1 class="title">Qt SCXML Media Player Example (Static)</h1> <span class="subtitle"></span> <!-- $$$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="qml"> <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="qml"> QT += widgets scxml </pre> <p>We then specify the state machine to compile:</p> <pre class="qml"> 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="qml"> <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="qml"> <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="qml"> 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-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> <li><a href="qtscxml-mediaplayer-widgets-static-mediaplayer-widgets-static-pro.html">mediaplayer-widgets-static/mediaplayer-widgets-static.pro</a></li> </ul> </div> <!-- @@@mediaplayer-widgets-static --> </div> </div> </div> </div> </div> <div class="footer"> <p> <acronym title="Copyright">©</acronym> 2017 The Qt Company Ltd. Documentation contributions included herein are the copyrights of their respective owners.<br> The documentation provided herein is licensed under the terms of the <a href="http://www.gnu.org/licenses/fdl.html">GNU Free Documentation License version 1.3</a> as published by the Free Software Foundation.<br> Qt and respective logos are trademarks of The Qt Company Ltd. in Finland and/or other countries worldwide. All other trademarks are property of their respective owners. </p> </div> </body> </html>