<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html>
<html lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<!-- digitalclock.qdoc -->
<title>Digital Clock Example | Qt Widgets 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="qtwidgets-index.html">Qt Widgets</a></td><td ><a href="examples-widgets.html">Qt Widgets Examples</a></td><td >Digital Clock Example</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="#digitalclock-class-definition">DigitalClock Class Definition</a></li>
<li class="level1"><a href="#digitalclock-class-implementation">DigitalClock Class Implementation</a></li>
</ul>
</div>
<div class="sidebar-content" id="sidebar-content"></div></div>
<h1 class="title">Digital Clock Example</h1>
<span class="subtitle"></span>
<!-- $$$widgets/digitalclock-description -->
<div class="descr"> <a name="details"></a>
<div class="border"><p class="centerAlign"><img src="images/digitalclock-example.png" alt="" /></p></div><p class="figCaption">Screenshot of the Digital Clock example</p>
<p>This example also demonstrates how <a href="../qtcore/qtimer.html">QTimer</a> can be used to update a widget at regular intervals.</p>
<a name="digitalclock-class-definition"></a>
<h2 id="digitalclock-class-definition">DigitalClock Class Definition</h2>
<p>The <code>DigitalClock</code> class provides a clock widget showing the time with hours and minutes separated by a blinking colon. We subclass <a href="qlcdnumber.html">QLCDNumber</a> and implement a private slot called <code>showTime()</code> to update the clock display:</p>
<pre class="cpp">
<span class="keyword">class</span> DigitalClock : <span class="keyword">public</span> <span class="type"><a href="qlcdnumber.html">QLCDNumber</a></span>
{
Q_OBJECT
<span class="keyword">public</span>:
DigitalClock(<span class="type"><a href="qwidget.html">QWidget</a></span> <span class="operator">*</span>parent <span class="operator">=</span> <span class="number">0</span>);
<span class="keyword">private</span> <span class="keyword">slots</span>:
<span class="type">void</span> showTime();
};
</pre>
<a name="digitalclock-class-implementation"></a>
<h2 id="digitalclock-class-implementation">DigitalClock Class Implementation</h2>
<pre class="cpp">
DigitalClock<span class="operator">::</span>DigitalClock(<span class="type"><a href="qwidget.html">QWidget</a></span> <span class="operator">*</span>parent)
: <span class="type"><a href="qlcdnumber.html">QLCDNumber</a></span>(parent)
{
setSegmentStyle(Filled);
<span class="type"><a href="../qtcore/qtimer.html">QTimer</a></span> <span class="operator">*</span>timer <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="../qtcore/qtimer.html">QTimer</a></span>(<span class="keyword">this</span>);
connect(timer<span class="operator">,</span> SIGNAL(timeout())<span class="operator">,</span> <span class="keyword">this</span><span class="operator">,</span> SLOT(showTime()));
timer<span class="operator">-</span><span class="operator">></span>start(<span class="number">1000</span>);
showTime();
setWindowTitle(tr(<span class="string">"Digital Clock"</span>));
resize(<span class="number">150</span><span class="operator">,</span> <span class="number">60</span>);
}
</pre>
<p>In the constructor, we first change the look of the LCD numbers. The <a href="qlcdnumber.html#SegmentStyle-enum">QLCDNumber::Filled</a> style produces raised segments filled with the foreground color (typically black). We also set up a one-second timer to keep track of the current time, and we connect its <a href="../qtcore/qtimer.html#timeout">timeout()</a> signal to the private <code>showTime()</code> slot so that the display is updated every second. Then, we call the <code>showTime()</code> slot; without this call, there would be a one-second delay at startup before the time is shown.</p>
<pre class="cpp">
<span class="type">void</span> DigitalClock<span class="operator">::</span>showTime()
{
<span class="type"><a href="../qtcore/qtime.html">QTime</a></span> time <span class="operator">=</span> <span class="type"><a href="../qtcore/qtime.html">QTime</a></span><span class="operator">::</span>currentTime();
<span class="type"><a href="../qtcore/qstring.html">QString</a></span> text <span class="operator">=</span> time<span class="operator">.</span>toString(<span class="string">"hh:mm"</span>);
<span class="keyword">if</span> ((time<span class="operator">.</span>second() <span class="operator">%</span> <span class="number">2</span>) <span class="operator">=</span><span class="operator">=</span> <span class="number">0</span>)
text<span class="operator">[</span><span class="number">2</span><span class="operator">]</span> <span class="operator">=</span> <span class="char">' '</span>;
display(text);
}
</pre>
<p>The <code>showTime()</code> slot is called whenever the clock display needs to be updated.</p>
<p>The current time is converted into a string with the format "hh:mm". When <a href="../qtcore/qtime.html#second">QTime::second</a>() is a even number, the colon in the string is replaced with a space. This makes the colon appear and vanish every other second.</p>
<p>Finally, we call <a href="qlcdnumber.html#display">QLCDNumber::display</a>() to update the widget.</p>
<p>Files:</p>
<ul>
<li><a href="qtwidgets-widgets-digitalclock-digitalclock-cpp.html">widgets/digitalclock/digitalclock.cpp</a></li>
<li><a href="qtwidgets-widgets-digitalclock-digitalclock-h.html">widgets/digitalclock/digitalclock.h</a></li>
<li><a href="qtwidgets-widgets-digitalclock-main-cpp.html">widgets/digitalclock/main.cpp</a></li>
<li><a href="qtwidgets-widgets-digitalclock-digitalclock-pro.html">widgets/digitalclock/digitalclock.pro</a></li>
</ul>
</div>
<!-- @@@widgets/digitalclock -->
</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>
distrib
>
Mageia
>
6
>
armv5tl
>
media
>
core-updates
>
by-pkgid
>
768f7d9f703884aa2562bf0a651086df
>
files
>
4483
