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Breadcrumbs go here --> <li><a href="all-examples.html">Examples</a></li> <li>Digital Clock Example</li> </ul> </div> <div class="toolbuttons toolblock"> <ul> <li id="smallA" class="t_button">A</li> <li id="medA" class="t_button active">A</li> <li id="bigA" class="t_button">A</li> <li id="print" class="t_button"><a href="javascript:this.print();"> <span>Print</span></a></li> </ul> </div> </div> <div class="content mainContent"> <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> <h1 class="title">Digital Clock Example</h1> <span class="subtitle"></span> <!-- $$$widgets/digitalclock-description --> <div class="descr"> <a name="details"></a> <p>Files:</p> <ul> <li><a href="widgets-digitalclock-digitalclock-cpp.html">widgets/digitalclock/digitalclock.cpp</a></li> <li><a href="widgets-digitalclock-digitalclock-h.html">widgets/digitalclock/digitalclock.h</a></li> <li><a href="widgets-digitalclock-main-cpp.html">widgets/digitalclock/main.cpp</a></li> <li><a href="widgets-digitalclock-digitalclock-pro.html">widgets/digitalclock/digitalclock.pro</a></li> </ul> <p>The Digital Clock example shows how to use <a href="qlcdnumber.html">QLCDNumber</a> to display a number with LCD-like digits.<p class="centerAlign"><img src="images/digitalclock-example.png" alt="Screenshot of the Digital Clock example" /></p><p>This example also demonstrates how <a href="qtimer.html">QTimer</a> can be used to update a widget at regular intervals.</p> <a name="digitalclock-class-definition"></a> <h2>DigitalClock Class Definition</h2> <p>The <tt>DigitalClock</tt> 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 <tt>showTime()</tt> 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>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="qtimer.html">QTimer</a></span> <span class="operator">*</span>timer <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="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="qtimer.html#timeout">timeout()</a> signal to the private <tt>showTime()</tt> slot so that the display is updated every second. Then, we call the <tt>showTime()</tt> 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="qtime.html">QTime</a></span> time <span class="operator">=</span> <span class="type"><a href="qtime.html">QTime</a></span><span class="operator">::</span>currentTime(); <span class="type"><a href="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 <tt>showTime()</tt> 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="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#intValue-prop">QLCDNumber::display</a>() to update the widget.</p> </div> <!-- @@@widgets/digitalclock --> </div> </div> </div> <div class="ft"> <span></span> </div> </div> <div class="footer"> <p> <acronym title="Copyright">©</acronym> 2013 Digia Plc and/or its subsidiaries. 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