<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE html> <html lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <!-- trafficlight-widgets-dynamic.qdoc --> <title>Qt SCXML Traffic Light Example (Dynamic) | Qt SCXML 5.12.6</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 5.12</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 Traffic Light Example (Dynamic)</td></tr></table><table class="buildversion"><tr> <td id="buildversion" width="100%" align="right"><a href="qtscxml-index.html">Qt 5.12.6 Reference Documentation</a></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="#dynamically-loading-the-state-machine">Dynamically Loading 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 Traffic Light Example (Dynamic)</h1> <span class="subtitle"></span> <!-- $$$trafficlight-widgets-dynamic-brief --> <p>A widget-based application that uses a dynamically loaded state machine to implement a traffic light.</p> <!-- @@@trafficlight-widgets-dynamic --> <!-- $$$trafficlight-widgets-dynamic-description --> <div class="descr"> <a name="details"></a> <p class="centerAlign"><img src="images/trafficlight.png" alt="" /></p><p><i>Traffic Light Example (Dynamic)</i> demonstrates how to connect to the active properties of a state in a dynamically loaded state machine.</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="dynamically-loading-the-state-machine"></a> <h2 id="dynamically-loading-the-state-machine">Dynamically Loading the State Machine</h2> <p>We link against the Qt SCXML module by adding the following line to the example <i>.pro</i> file:</p> <pre class="cpp"> QT += widgets scxml </pre> <p>We dynamically create the state machine in <i>trafficlight-widgets-dynamic.cpp</i>:</p> <pre class="cpp"> <span class="preprocessor">#include "../trafficlight-common/trafficlight.h"</span> <span class="preprocessor">#include <QApplication></span> <span class="preprocessor">#include <QTextStream></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); <span class="type"><a href="qscxmlstatemachine.html">QScxmlStateMachine</a></span> <span class="operator">*</span>machine <span class="operator">=</span> <span class="type"><a href="qscxmlstatemachine.html">QScxmlStateMachine</a></span><span class="operator">::</span>fromFile( <span class="type">QStringLiteral</span>(<span class="string">":statemachine.scxml"</span>)); <span class="keyword">if</span> (<span class="operator">!</span>machine<span class="operator">-</span><span class="operator">></span>parseErrors()<span class="operator">.</span>isEmpty()) { <span class="type">QTextStream</span> errs(stderr<span class="operator">,</span> <span class="type">QIODevice</span><span class="operator">::</span>WriteOnly); <span class="keyword">const</span> <span class="keyword">auto</span> errors <span class="operator">=</span> machine<span class="operator">-</span><span class="operator">></span>parseErrors(); <span class="keyword">for</span> (<span class="keyword">const</span> <span class="type"><a href="qscxmlerror.html">QScxmlError</a></span> <span class="operator">&</span>error : errors) { errs <span class="operator"><</span><span class="operator"><</span> error<span class="operator">.</span>toString(); } <span class="keyword">return</span> <span class="operator">-</span><span class="number">1</span>; } </pre> <p>And then instantiate it:</p> <pre class="cpp"> TrafficLight widget(machine); widget<span class="operator">.</span>show(); machine<span class="operator">-</span><span class="operator">></span>setParent(<span class="operator">&</span>widget); machine<span class="operator">-</span><span class="operator">></span>start(); <span class="keyword">return</span> app<span class="operator">.</span>exec(); } </pre> <a name="connecting-to-states"></a> <h2 id="connecting-to-states">Connecting to States</h2> <p>In the SCXML file, we specify states for each light: red, yellow, and green. In the <code><onentry></code> element, we specify the event to send when entering the state and the delay in seconds before sending the event. In the <code><transition></code> element, we specify the event that triggers the transition to the state specified by the <code>target</code> attribute:</p> <pre class="cpp"> <state id="red"> <onentry> <send event="startGoingGreen" delay="3s"/> </onentry> <transition event="startGoingGreen" target="redGoingGreen"/> </state> <state id="yellow" initial="greenGoingRed"> <state id="redGoingGreen"> <onentry> <send event="goGreen" delay="1s"/> </onentry> <transition event="goGreen" target="green"/> </state> <state id="greenGoingRed"> <onentry> <send event="goRed" delay="1s"/> </onentry> <transition event="goRed" target="red"/> </state> </state> <state id="green"> <onentry> <send event="startGoingRed" delay="3s"/> </onentry> <transition event="startGoingRed" target="greenGoingRed"/> </state> </pre> <p>We connect to the states as follows:</p> <pre class="cpp"> machine<span class="operator">-</span><span class="operator">></span>connectToState(<span class="type">QStringLiteral</span>(<span class="string">"red"</span>)<span class="operator">,</span> widget<span class="operator">-</span><span class="operator">></span>redLight()<span class="operator">,</span> <span class="operator">&</span>LightWidget<span class="operator">::</span>switchLight); machine<span class="operator">-</span><span class="operator">></span>connectToState(<span class="type">QStringLiteral</span>(<span class="string">"redGoingGreen"</span>)<span class="operator">,</span> widget<span class="operator">-</span><span class="operator">></span>redLight()<span class="operator">,</span> <span class="operator">&</span>LightWidget<span class="operator">::</span>switchLight); machine<span class="operator">-</span><span class="operator">></span>connectToState(<span class="type">QStringLiteral</span>(<span class="string">"yellow"</span>)<span class="operator">,</span> widget<span class="operator">-</span><span class="operator">></span>yellowLight()<span class="operator">,</span> <span class="operator">&</span>LightWidget<span class="operator">::</span>switchLight); machine<span class="operator">-</span><span class="operator">></span>connectToState(<span class="type">QStringLiteral</span>(<span class="string">"blinking"</span>)<span class="operator">,</span> widget<span class="operator">-</span><span class="operator">></span>yellowLight()<span class="operator">,</span> <span class="operator">&</span>LightWidget<span class="operator">::</span>switchLight); machine<span class="operator">-</span><span class="operator">></span>connectToState(<span class="type">QStringLiteral</span>(<span class="string">"green"</span>)<span class="operator">,</span> widget<span class="operator">-</span><span class="operator">></span>greenLight()<span class="operator">,</span> <span class="operator">&</span>LightWidget<span class="operator">::</span>switchLight); </pre> <p>Files:</p> <ul> <li><a href="qtscxml-trafficlight-widgets-dynamic-trafficlight-widgets-dynamic-cpp.html">trafficlight-widgets-dynamic/trafficlight-widgets-dynamic.cpp</a></li> <li><a href="qtscxml-trafficlight-widgets-dynamic-trafficlight-widgets-dynamic-pro.html">trafficlight-widgets-dynamic/trafficlight-widgets-dynamic.pro</a></li> <li><a href="qtscxml-trafficlight-widgets-dynamic-trafficlight-widgets-dynamic-qrc.html">trafficlight-widgets-dynamic/trafficlight-widgets-dynamic.qrc</a></li> </ul> </div> <!-- @@@trafficlight-widgets-dynamic --> </div> </div> </div> </div> </div> <div class="footer"> <p> <acronym title="Copyright">©</acronym> 2019 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>