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<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 Traffic Light QML Example (Static)</td></tr></table><table class="buildversion"><tr>
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<h3><a name="toc">Contents</a></h3>
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<li class="level1"><a href="#running-the-example">Running the Example</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 Traffic Light QML Example (Static)</h1>
<span class="subtitle"></span>
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<div class="descr"> <a name="details"></a>
<p class="centerAlign"><img src="images/trafficlight.png" alt="" /></p><p><i>Traffic Light QML Example (Static)</i> demonstrates how to connect to the active properties of a state in a state machine that is compiled to a class.</p>
<p>The UI is created using Qt Quick.</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="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 += qml scxml
</pre>
<p>We then specify the state machine to compile:</p>
<pre class="qml">
STATECHARTS = ../trafficlight-common/statemachine.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 state machine as follows:</p>
<pre class="qml">
import TrafficLightStateMachine 1.0
<span class="type">TrafficLight</span> {
<span class="name">stateMachine</span>: <span class="name">TrafficLightStateMachine</span> {
<span class="name">running</span>: <span class="number">true</span>
}
</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="qml">
<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="qml">
<span class="name">states</span>: [
<span class="type">State</span> {
<span class="name">name</span>: <span class="string">"Red"</span>
<span class="name">when</span>: <span class="name">stateMachine</span>.<span class="name">red</span>
<span class="type">PropertyChanges</span> {
<span class="name">target</span>: <span class="name">redLight</span>
<span class="name">opacity</span>: <span class="number">1</span>
}
},
<span class="type">State</span> {
<span class="name">name</span>: <span class="string">"RedGoingGreen"</span>
<span class="name">when</span>: <span class="name">stateMachine</span>.<span class="name">redGoingGreen</span>
<span class="type">PropertyChanges</span> {
<span class="name">target</span>: <span class="name">redLight</span>
<span class="name">opacity</span>: <span class="number">1</span>
}
<span class="type">PropertyChanges</span> {
<span class="name">target</span>: <span class="name">yellowLight</span>
<span class="name">opacity</span>: <span class="number">1</span>
}
},
<span class="type">State</span> {
<span class="name">name</span>: <span class="string">"Yellow"</span>
<span class="name">when</span>: <span class="name">stateMachine</span>.<span class="name">yellow</span> <span class="operator">||</span> <span class="name">stateMachine</span>.<span class="name">blinking</span>
<span class="type">PropertyChanges</span> {
<span class="name">target</span>: <span class="name">yellowLight</span>
<span class="name">opacity</span>: <span class="number">1</span>
}
},
<span class="type">State</span> {
<span class="name">name</span>: <span class="string">"Green"</span>
<span class="name">when</span>: <span class="name">stateMachine</span>.<span class="name">green</span>
<span class="type">PropertyChanges</span> {
<span class="name">target</span>: <span class="name">greenLight</span>
<span class="name">opacity</span>: <span class="number">1</span>
}
}
]
</pre>
<p>Files:</p>
<ul>
<li><a href="qtscxml-trafficlight-qml-static-statemachine-cpp.html">trafficlight-qml-static/statemachine.cpp</a></li>
<li><a href="qtscxml-trafficlight-qml-static-statemachine-h.html">trafficlight-qml-static/statemachine.h</a></li>
<li><a href="qtscxml-trafficlight-qml-static-trafficlight-qml-static-cpp.html">trafficlight-qml-static/trafficlight-qml-static.cpp</a></li>
<li><a href="qtscxml-trafficlight-qml-static-trafficlight-qml-static-qml.html">trafficlight-qml-static/trafficlight-qml-static.qml</a></li>
<li><a href="qtscxml-trafficlight-qml-static-trafficlight-qml-static-pro.html">trafficlight-qml-static/trafficlight-qml-static.pro</a></li>
<li><a href="qtscxml-trafficlight-qml-static-trafficlight-qml-static-qrc.html">trafficlight-qml-static/trafficlight-qml-static.qrc</a></li>
</ul>
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