<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE html> <html lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <!-- twowaybutton.qdoc --> <title>Two-way Button Example | Qt Widgets 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="qtwidgets-index.html">Qt Widgets</a></td><td >Two-way Button Example</td></tr></table><table class="buildversion"><tr> <td id="buildversion" width="100%" align="right"><a href="qtwidgets-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="sidebar-content" id="sidebar-content"></div></div> <h1 class="title">Two-way Button Example</h1> <span class="subtitle"></span> <!-- $$$statemachine/twowaybutton-brief --> <p>The Two-way button example shows how to use <a href="../qtcore/statemachine-api.html">The State Machine Framework</a> to implement a simple state machine that toggles the current state when a button is clicked.</p> <!-- @@@statemachine/twowaybutton --> <!-- $$$statemachine/twowaybutton-description --> <div class="descr"> <a name="details"></a> <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="../qtcore/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="../qtcore/qstate.html">QState</a></span> <span class="operator">*</span>off <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="../qtcore/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="../qtcore/qstate.html">QState</a></span> <span class="operator">*</span>on <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="../qtcore/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; <code>on</code> and <code>off</code>. 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 <code>off</code> state and the button is clicked, it will transition to the <code>on</code> state; when the state machine is in the <code>on</code> state and the button is clicked, it will transition to the <code>off</code> 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 <code>off</code>; this is the state the state machine will immediately transition to once the state machine is started.</p> <pre class="cpp"> 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="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> <p>Files:</p> <ul> <li><a href="qtwidgets-statemachine-twowaybutton-main-cpp.html">statemachine/twowaybutton/main.cpp</a></li> <li><a href="qtwidgets-statemachine-twowaybutton-twowaybutton-pro.html">statemachine/twowaybutton/twowaybutton.pro</a></li> </ul> </div> <!-- @@@statemachine/twowaybutton --> </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>