<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html>
<html lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<!-- addressbook-tutorial.qdoc -->
<title>Part 5 - Adding a Find Function | 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 >Part 5 - Adding a Find Function</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="#defining-the-finddialog-class">Defining the FindDialog Class</a></li>
<li class="level1"><a href="#implementing-the-finddialog-class">Implementing the FindDialog Class</a></li>
<li class="level1"><a href="#defining-the-addressbook-class">Defining the AddressBook Class</a></li>
<li class="level1"><a href="#implementing-the-addressbook-class">Implementing the AddressBook Class</a></li>
</ul>
</div>
<div class="sidebar-content" id="sidebar-content"></div></div>
<h1 class="title">Part 5 - Adding a Find Function</h1>
<span class="subtitle"></span>
<!-- $$$tutorials/addressbook/part5-description -->
<div class="descr"> <a name="details"></a>
<p>Here we look at ways to locate contacts and addresses in the address book.</p>
<p class="centerAlign"><img src="images/addressbook-tutorial-part5-screenshot.png" alt="" /></p><p>As we add contacts to our address book, it becomes tedious to navigate the list with the <i>Next</i> and <i>Previous</i> buttons. A <i>Find</i> function would be more efficient. The screenshot above shows the <i>Find</i> button and its position on the panel of buttons.</p>
<p>When the user clicks on the <i>Find</i> button, it is useful to display a dialog that prompts for a contact's name. Qt provides <a href="qdialog.html">QDialog</a>, which we subclass here to implement a <code>FindDialog</code> class.</p>
<a name="defining-the-finddialog-class"></a>
<h2 id="defining-the-finddialog-class">Defining the FindDialog Class</h2>
<p class="centerAlign"><img src="images/addressbook-tutorial-part5-finddialog.png" alt="" /></p><p>In order to subclass <a href="qdialog.html">QDialog</a>, we first include the header for <a href="qdialog.html">QDialog</a> in the <code>finddialog.h</code> file. Also, we use forward declaration to declare <a href="qlineedit.html">QLineEdit</a> and <a href="qpushbutton.html">QPushButton</a> since we will be using those widgets in our dialog class.</p>
<p>As in our <code>AddressBook</code> class, the <code>FindDialog</code> class includes the <a href="../qtcore/qobject.html#Q_OBJECT">Q_OBJECT</a> macro and its constructor is defined to accept a parent <a href="qwidget.html">QWidget</a>, even though the dialog will be opened as a separate window.</p>
<pre class="cpp">
<span class="preprocessor">#include <QDialog></span>
<span class="keyword">class</span> <span class="type"><a href="qlineedit.html">QLineEdit</a></span>;
<span class="keyword">class</span> <span class="type"><a href="qpushbutton.html">QPushButton</a></span>;
<span class="keyword">class</span> FindDialog : <span class="keyword">public</span> <span class="type"><a href="qdialog.html">QDialog</a></span>
{
Q_OBJECT
<span class="keyword">public</span>:
FindDialog(<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="type"><a href="../qtcore/qstring.html">QString</a></span> getFindText();
<span class="keyword">public</span> <span class="keyword">slots</span>:
<span class="type">void</span> findClicked();
<span class="keyword">private</span>:
<span class="type"><a href="qpushbutton.html">QPushButton</a></span> <span class="operator">*</span>findButton;
<span class="type"><a href="qlineedit.html">QLineEdit</a></span> <span class="operator">*</span>lineEdit;
<span class="type"><a href="../qtcore/qstring.html">QString</a></span> findText;
};
</pre>
<p>We define a public function, <code>getFindText()</code>, to be used by classes that instantiate <code>FindDialog</code>. This function allows these classes to obtain the search string entered by the user. A public slot, <code>findClicked()</code>, is also defined to handle the search string when the user clicks the <b>Find</b> button.</p>
<p>Lastly, we define the private variables, <code>findButton</code>, <code>lineEdit</code> and <code>findText</code>, corresponding to the <b>Find</b> button, the line edit into which the user types the search string, and an internal string used to store the search string for later use.</p>
<a name="implementing-the-finddialog-class"></a>
<h2 id="implementing-the-finddialog-class">Implementing the FindDialog Class</h2>
<p>Within the constructor of <code>FindDialog</code>, we set up the private variables, <code>lineEdit</code>, <code>findButton</code> and <code>findText</code>. We use a <a href="qhboxlayout.html">QHBoxLayout</a> to position the widgets.</p>
<pre class="cpp">
FindDialog<span class="operator">::</span>FindDialog(<span class="type"><a href="qwidget.html">QWidget</a></span> <span class="operator">*</span>parent)
: <span class="type"><a href="qdialog.html">QDialog</a></span>(parent)
{
<span class="type"><a href="qlabel.html">QLabel</a></span> <span class="operator">*</span>findLabel <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="qlabel.html">QLabel</a></span>(tr(<span class="string">"Enter the name of a contact:"</span>));
lineEdit <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="qlineedit.html">QLineEdit</a></span>;
findButton <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="qpushbutton.html">QPushButton</a></span>(tr(<span class="string">"&Find"</span>));
findText <span class="operator">=</span> <span class="string">""</span>;
<span class="type"><a href="qhboxlayout.html">QHBoxLayout</a></span> <span class="operator">*</span>layout <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="qhboxlayout.html">QHBoxLayout</a></span>;
layout<span class="operator">-</span><span class="operator">></span>addWidget(findLabel);
layout<span class="operator">-</span><span class="operator">></span>addWidget(lineEdit);
layout<span class="operator">-</span><span class="operator">></span>addWidget(findButton);
setLayout(layout);
setWindowTitle(tr(<span class="string">"Find a Contact"</span>));
connect(findButton<span class="operator">,</span> SIGNAL(clicked())<span class="operator">,</span> <span class="keyword">this</span><span class="operator">,</span> SLOT(findClicked()));
connect(findButton<span class="operator">,</span> SIGNAL(clicked())<span class="operator">,</span> <span class="keyword">this</span><span class="operator">,</span> SLOT(accept()));
}
</pre>
<p>We set the layout and window title, as well as connect the signals to their respective slots. Notice that <code>findButton</code>'s <a href="qabstractbutton.html#clicked">clicked()</a> signal is connected to <code>findClicked()</code> and <a href="qdialog.html#accept">accept()</a>. The <a href="qdialog.html#accept">accept()</a> slot provided by <a href="qdialog.html">QDialog</a> hides the dialog and sets the result code to <a href="qdialog.html#DialogCode-enum">Accepted</a>. We use this function to help <code>AddressBook</code>'s <code>findContact()</code> function know when the <code>FindDialog</code> object has been closed. We will explain this logic in further detail when discussing the <code>findContact()</code> function.</p>
<p class="centerAlign"><img src="images/addressbook-tutorial-part5-signals-and-slots.png" alt="" /></p><p>In <code>findClicked()</code>, we validate <code>lineEdit</code> to ensure that the user did not click the <b>Find</b> button without entering a contact's name. Then, we set <code>findText</code> to the search string, extracted from <code>lineEdit</code>. After that, we clear the contents of <code>lineEdit</code> and hide the dialog.</p>
<pre class="cpp">
<span class="type">void</span> FindDialog<span class="operator">::</span>findClicked()
{
<span class="type"><a href="../qtcore/qstring.html">QString</a></span> text <span class="operator">=</span> lineEdit<span class="operator">-</span><span class="operator">></span>text();
<span class="keyword">if</span> (text<span class="operator">.</span>isEmpty()) {
<span class="type"><a href="qmessagebox.html">QMessageBox</a></span><span class="operator">::</span>information(<span class="keyword">this</span><span class="operator">,</span> tr(<span class="string">"Empty Field"</span>)<span class="operator">,</span>
tr(<span class="string">"Please enter a name."</span>));
<span class="keyword">return</span>;
} <span class="keyword">else</span> {
findText <span class="operator">=</span> text;
lineEdit<span class="operator">-</span><span class="operator">></span>clear();
hide();
}
}
</pre>
<p>The <code>findText</code> variable has a public getter function, <code>getFindText()</code>, associated with it. Since we only ever set <code>findText</code> directly in both the constructor and in the <code>findClicked()</code> function, we do not create a setter function to accompany <code>getFindText()</code>. Because <code>getFindText()</code> is public, classes instantiating and using <code>FindDialog</code> can always access the search string that the user has entered and accepted.</p>
<pre class="cpp">
<span class="type"><a href="../qtcore/qstring.html">QString</a></span> FindDialog<span class="operator">::</span>getFindText()
{
<span class="keyword">return</span> findText;
}
</pre>
<a name="defining-the-addressbook-class"></a>
<h2 id="defining-the-addressbook-class">Defining the AddressBook Class</h2>
<p>To ensure we can use <code>FindDialog</code> from within our <code>AddressBook</code> class, we include <code>finddialog.h</code> in the <code>addressbook.h</code> file.</p>
<pre class="cpp">
<span class="preprocessor">#include "finddialog.h"</span>
</pre>
<p>So far, all our address book features have a <a href="qpushbutton.html">QPushButton</a> and a corresponding slot. Similarly, for the <b>Find</b> feature we have <code>findButton</code> and <code>findContact()</code>.</p>
<p>The <code>findButton</code> is declared as a private variable and the <code>findContact()</code> function is declared as a public slot.</p>
<pre class="cpp">
<span class="type">void</span> findContact();
...
<span class="type"><a href="qpushbutton.html">QPushButton</a></span> <span class="operator">*</span>findButton;
</pre>
<p>Lastly, we declare the private variable, <code>dialog</code>, which we will use to refer to an instance of <code>FindDialog</code>.</p>
<pre class="cpp">
FindDialog <span class="operator">*</span>dialog;
</pre>
<p>Once we have instantiated a dialog, we will want to use it more than once; using a private variable allows us to refer to it from more than one place in the class.</p>
<a name="implementing-the-addressbook-class"></a>
<h2 id="implementing-the-addressbook-class">Implementing the AddressBook Class</h2>
<p>Within the <code>AddressBook</code> class's constructor, we instantiate our private objects, <code>findButton</code> and <code>findDialog</code>:</p>
<pre class="cpp">
findButton <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="qpushbutton.html">QPushButton</a></span>(tr(<span class="string">"&Find"</span>));
findButton<span class="operator">-</span><span class="operator">></span>setEnabled(<span class="keyword">false</span>);
...
dialog <span class="operator">=</span> <span class="keyword">new</span> FindDialog(<span class="keyword">this</span>);
</pre>
<p>Next, we connect the <code>findButton</code>'s <a href="qabstractbutton.html#clicked">clicked()</a> signal to <code>findContact()</code>.</p>
<pre class="cpp">
connect(findButton<span class="operator">,</span> SIGNAL(clicked())<span class="operator">,</span> <span class="keyword">this</span><span class="operator">,</span> SLOT(findContact()));
</pre>
<p>Now all that is left is the code for our <code>findContact()</code> function:</p>
<pre class="cpp">
<span class="type">void</span> AddressBook<span class="operator">::</span>findContact()
{
dialog<span class="operator">-</span><span class="operator">></span>show();
<span class="keyword">if</span> (dialog<span class="operator">-</span><span class="operator">></span>exec() <span class="operator">=</span><span class="operator">=</span> <span class="type"><a href="qdialog.html">QDialog</a></span><span class="operator">::</span>Accepted) {
<span class="type"><a href="../qtcore/qstring.html">QString</a></span> contactName <span class="operator">=</span> dialog<span class="operator">-</span><span class="operator">></span>getFindText();
<span class="keyword">if</span> (contacts<span class="operator">.</span>contains(contactName)) {
nameLine<span class="operator">-</span><span class="operator">></span>setText(contactName);
addressText<span class="operator">-</span><span class="operator">></span>setText(contacts<span class="operator">.</span>value(contactName));
} <span class="keyword">else</span> {
<span class="type"><a href="qmessagebox.html">QMessageBox</a></span><span class="operator">::</span>information(<span class="keyword">this</span><span class="operator">,</span> tr(<span class="string">"Contact Not Found"</span>)<span class="operator">,</span>
tr(<span class="string">"Sorry, \"%1\" is not in your address book."</span>)<span class="operator">.</span>arg(contactName));
<span class="keyword">return</span>;
}
}
updateInterface(NavigationMode);
}
</pre>
<p>We start out by displaying the <code>FindDialog</code> instance, <code>dialog</code>. This is when the user enters a contact name to look up. Once the user clicks the dialog's <code>findButton</code>, the dialog is hidden and the result code is set to <a href="qdialog.html#DialogCode-enum">QDialog::Accepted</a>. This ensures that our <code>if</code> statement is always true.</p>
<p>We then proceed to extract the search string, which in this case is <code>contactName</code>, using <code>FindDialog</code>'s <code>getFindText()</code> function. If the contact exists in our address book, we display it immediately. Otherwise, we display the <a href="qmessagebox.html">QMessageBox</a> shown below to indicate that their search failed.</p>
<p class="centerAlign"><img src="images/addressbook-tutorial-part5-notfound.png" alt="" /></p><p>Files:</p>
<ul>
<li><a href="qtwidgets-tutorials-addressbook-part5-addressbook-cpp.html">tutorials/addressbook/part5/addressbook.cpp</a></li>
<li><a href="qtwidgets-tutorials-addressbook-part5-addressbook-h.html">tutorials/addressbook/part5/addressbook.h</a></li>
<li><a href="qtwidgets-tutorials-addressbook-part5-finddialog-cpp.html">tutorials/addressbook/part5/finddialog.cpp</a></li>
<li><a href="qtwidgets-tutorials-addressbook-part5-finddialog-h.html">tutorials/addressbook/part5/finddialog.h</a></li>
<li><a href="qtwidgets-tutorials-addressbook-part5-main-cpp.html">tutorials/addressbook/part5/main.cpp</a></li>
<li><a href="qtwidgets-tutorials-addressbook-part5-part5-pro.html">tutorials/addressbook/part5/part5.pro</a></li>
</ul>
</div>
<!-- @@@tutorials/addressbook/part5 -->
</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
>
4420
