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<a href="index.html" class="qtref"><span>Qt Reference Documentation</span></a>
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<h1 class="title">Two-way Button Example</h1>
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<p>Files:</p>
<ul>
<li><a href="statemachine-twowaybutton-main-cpp.html">statemachine/twowaybutton/main.cpp</a></li>
<li><a href="statemachine-twowaybutton-twowaybutton-pro.html">statemachine/twowaybutton/twowaybutton.pro</a></li>
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<p>The Two-way button example shows how to use <a href="statemachine-api.html">The State Machine Framework</a> to implement a simple state machine that toggles the current state when a button is clicked.<pre class="cpp"> <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"><a href="qapplication.html">QApplication</a></span> app(argc<span class="operator">,</span> argv);
<span class="type"><a href="qpushbutton.html">QPushButton</a></span> button;
<span class="type"><a href="qstatemachine.html">QStateMachine</a></span> machine;</pre>
<p>The application's main() function begins by constructing the application object, a button and a state machine.</p>
<pre class="cpp"> <span class="type"><a href="qstate.html">QState</a></span> <span class="operator">*</span>off <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="qstate.html">QState</a></span>();
off<span class="operator">-</span><span class="operator">></span>assignProperty(<span class="operator">&</span>button<span class="operator">,</span> <span class="string">"text"</span><span class="operator">,</span> <span class="string">"Off"</span>);
off<span class="operator">-</span><span class="operator">></span>setObjectName(<span class="string">"off"</span>);
<span class="type"><a href="qstate.html">QState</a></span> <span class="operator">*</span>on <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="qstate.html">QState</a></span>();
on<span class="operator">-</span><span class="operator">></span>setObjectName(<span class="string">"on"</span>);
on<span class="operator">-</span><span class="operator">></span>assignProperty(<span class="operator">&</span>button<span class="operator">,</span> <span class="string">"text"</span><span class="operator">,</span> <span class="string">"On"</span>);</pre>
<p>The state machine has two states; <tt>on</tt> and <tt>off</tt>. When either state is entered, the text of the button will be set accordingly.</p>
<pre class="cpp"> off<span class="operator">-</span><span class="operator">></span>addTransition(<span class="operator">&</span>button<span class="operator">,</span> SIGNAL(clicked())<span class="operator">,</span> on);
on<span class="operator">-</span><span class="operator">></span>addTransition(<span class="operator">&</span>button<span class="operator">,</span> SIGNAL(clicked())<span class="operator">,</span> off);</pre>
<p>When the state machine is in the <tt>off</tt> state and the button is clicked, it will transition to the <tt>on</tt> state; when the state machine is in the <tt>on</tt> state and the button is clicked, it will transition to the <tt>off</tt> state.</p>
<pre class="cpp"> machine<span class="operator">.</span>addState(off);
machine<span class="operator">.</span>addState(on);</pre>
<p>The states are added to the state machine; they become top-level (sibling) states.</p>
<pre class="cpp"> machine<span class="operator">.</span>setInitialState(off);
machine<span class="operator">.</span>start();</pre>
<p>The initial state is <tt>off</tt>; this is the state the state machine will immediately transition to once the state machine is started.</p>
<pre class="cpp"> <span class="preprocessor">#if defined(Q_OS_SYMBIAN)</span>
button<span class="operator">.</span>showMaximized();
<span class="preprocessor">#elif defined(Q_WS_MAEMO_5) || defined(Q_WS_SIMULATOR)</span>
button<span class="operator">.</span>show();
<span class="preprocessor">#else</span>
button<span class="operator">.</span>resize(<span class="number">100</span><span class="operator">,</span> <span class="number">50</span>);
button<span class="operator">.</span>show();
<span class="preprocessor">#endif</span>
<span class="keyword">return</span> app<span class="operator">.</span>exec();
}</pre>
<p>Finally, the button is resized and made visible, and the application event loop is entered.</p>
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