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<li>Carnet d'adresses 3 - Navigation entre les éléments</li>
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<h3><a name="toc">Contents</a></h3>
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<li class="level1"><a href="#d-finition-de-la-classe-addressbook">Définition de la classe AddressBook</a></li>
<li class="level1"><a href="#impl-mentation-de-la-classe-addressbook">Implémentation de la classe AddressBook</a></li>
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<h1 class="title">Carnet d'adresses 3 - Navigation entre les éléments</h1>
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<!-- $$$tutorials/addressbook-fr/part3-description -->
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<p>Files:</p>
<ul>
<li><a href="tutorials-addressbook-fr-part3-addressbook-cpp.html">tutorials/addressbook-fr/part3/addressbook.cpp</a></li>
<li><a href="tutorials-addressbook-fr-part3-addressbook-h.html">tutorials/addressbook-fr/part3/addressbook.h</a></li>
<li><a href="tutorials-addressbook-fr-part3-main-cpp.html">tutorials/addressbook-fr/part3/main.cpp</a></li>
<li><a href="tutorials-addressbook-fr-part3-part3-pro.html">tutorials/addressbook-fr/part3/part3.pro</a></li>
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<p>L'application "Carnet d'adresses" est maintenant à moitié terminée. Il nous faut maintenant ajouter quelques fonctions pour naviguer entre les contacts. Avant de commencer, il faut se décider sur le type de structure de données le plus approprié pour stocker les contacts.</p>
<p>Dans le chapitre 2, nous avons utilisé un <a href="qmap.html">QMap</a> utilisant des paires clé-valeur, avec le nom du contact comme <i>clé</i>, et l'adresse du contact comme <i>valeur</i>. Cela fonctionnait bien jusqu'ici, mais pour ajouter la navigation entre les entrées, quelques améliorations sont nécessaires.</p>
<p>Nous améliorerons le <a href="qmap.html">QMap</a> en le faisant ressembler à une structure de données similaire à une liste liée, où tous les éléments sont connectés, y compris le premier et le dernier élément. La figure ci-dessous illustre cette structure de donnée.</p>
<p class="centerAlign"><img src="images/addressbook-tutorial-part3-linkedlist.png" alt="" /></p><a name="d-finition-de-la-classe-addressbook"></a>
<h2>Définition de la classe AddressBook</h2>
<p>Pour ajouter les fonctions de navigation au carnet d'adresses, nous avons besoin de deux slots supplémentaires dans notre classe <tt>AddressBook</tt>: <tt>next()</tt> et <tt>previous()</tt>. Ceux-ci sont ajoutés au fichier addressbook.h:</p>
<pre class="cpp"> <span class="type">void</span> next();
<span class="type">void</span> previous();</pre>
<p>Nous avons aussi besoin de deux nouveaux objets <a href="qpushbutton.html">QPushButton</a>, nous ajoutons donc les variables privées <tt>nextButton</tt> et <tt>previousButton</tt>.</p>
<pre class="cpp"> <span class="type"><a href="qpushbutton.html">QPushButton</a></span> <span class="operator">*</span>nextButton;
<span class="type"><a href="qpushbutton.html">QPushButton</a></span> <span class="operator">*</span>previousButton;</pre>
<a name="impl-mentation-de-la-classe-addressbook"></a>
<h2>Implémentation de la classe AddressBook</h2>
<p>A l'intérieur du constructeur de <tt>AddressBook</tt>, dans <tt>addressbook.cpp</tt>, nous instancions <tt>nextButton</tt> et <tt>previousButton</tt> et nous les désactivons par défaut. Nous faisons ceci car la navigation ne doit être activée que lorsqu'il y a plus d'un contact dans le carnet d'adresses.</p>
<pre class="cpp"> nextButton <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="qpushbutton.html">QPushButton</a></span>(tr(<span class="string">"&Next"</span>));
nextButton<span class="operator">-</span><span class="operator">></span>setEnabled(<span class="keyword">false</span>);
previousButton <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="qpushbutton.html">QPushButton</a></span>(tr(<span class="string">"&Previous"</span>));
previousButton<span class="operator">-</span><span class="operator">></span>setEnabled(<span class="keyword">false</span>);</pre>
<p>Nous connectons alors ces boutons à leur slots respectifs:</p>
<pre class="cpp"> connect(nextButton<span class="operator">,</span> SIGNAL(clicked())<span class="operator">,</span> <span class="keyword">this</span><span class="operator">,</span> SLOT(next()));
connect(previousButton<span class="operator">,</span> SIGNAL(clicked())<span class="operator">,</span> <span class="keyword">this</span><span class="operator">,</span> SLOT(previous()));</pre>
<p>L'image ci-dessous montre l'interface utilisateur que nous allons créer. Remarquez que cela ressemble de plus en plus à l'interface du programme complet.</p>
<p class="centerAlign"><img src="images/addressbook-tutorial-part3-screenshot.png" alt="" /></p><p>Nous suivons les conventions pour les fonctions <tt>next()</tt> et <tt>previous()</tt> en plaçant <tt>nextButton</tt> à droite et <tt>previousButton</tt> à gauche. Pour faire cette mise en page intuitive, nous utilisons un <a href="qhboxlayout.html">QHBoxLayout</a> pour placer les widgets côte à côte:</p>
<pre class="cpp"> <span class="type"><a href="qhboxlayout.html">QHBoxLayout</a></span> <span class="operator">*</span>buttonLayout2 <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="qhboxlayout.html">QHBoxLayout</a></span>;
buttonLayout2<span class="operator">-</span><span class="operator">></span>addWidget(previousButton);
buttonLayout2<span class="operator">-</span><span class="operator">></span>addWidget(nextButton);</pre>
<p>L'objet <a href="qhboxlayout.html">QHBoxLayout</a>, <tt>buttonLayout2</tt>, est ensuite ajouté à <tt>mainLayout</tt>.</p>
<pre class="cpp"> mainLayout<span class="operator">-</span><span class="operator">></span>addLayout(buttonLayout2<span class="operator">,</span> <span class="number">2</span><span class="operator">,</span> <span class="number">1</span>);</pre>
<p>La figure ci-dessous montre les systèmes de coordonnées pour les widgets du <tt>mainLayout</tt>.</p>
<p class="centerAlign"><img src="images/addressbook-tutorial-part3-labeled-layout.png" alt="" /></p><p>Dans notre méthode <tt>addContact()</tt>, nous avons desactivé ces boutons pour être sûr que l'utilisateur n'utilise pas la navigation lors de l'ajout d'un contact.</p>
<pre class="cpp"> nextButton<span class="operator">-</span><span class="operator">></span>setEnabled(<span class="keyword">false</span>);
previousButton<span class="operator">-</span><span class="operator">></span>setEnabled(<span class="keyword">false</span>);</pre>
<p>Dans notre méthode <tt>submitContact()</tt>, nous activons les boutons de navigation, <tt>nextButton</tt> et <tt>previousButton</tt>, en fonction de la taille de <tt>contacts</tt>. Commen mentionné plus tôt, la navigation n'est activée que si il y a plus d'un contact dans le carnet d'adresses. Les lignes suivantes montrent comment faire cela:</p>
<pre class="cpp"> <span class="type">int</span> number <span class="operator">=</span> contacts<span class="operator">.</span>size();
nextButton<span class="operator">-</span><span class="operator">></span>setEnabled(number <span class="operator">></span> <span class="number">1</span>);
previousButton<span class="operator">-</span><span class="operator">></span>setEnabled(number <span class="operator">></span> <span class="number">1</span>);</pre>
<p>Nous incluons aussi ces lignes de code dans le bouton <tt>cancel()</tt>.</p>
<p>Souvenez vous que nous voulons émuler une liste-liée ciruculaire à l'aide de l'objet <a href="qmap.html">QMap</a>, <tt>contacts</tt>. Pour faire cela, nous obtenons un itérateur sur <tt>contact</tt> dans la méthode <tt>next()</tt>, et ensuite:</p>
<ul>
<li>Si l'itérateur n'est pas à la fin de <tt>contacts</tt>, nous l'incrémentons</li>
<li>Si l'itérateur est à la fin de <tt>contacts</tt>, nous changeons sa position jusqu'au début de <tt>contacts</tt>. Cela donne l'illusion que notre <a href="qmap.html">QMap</a> fonctionne comme une liste circulaire.</li>
</ul>
<pre class="cpp"> <span class="type">void</span> AddressBook<span class="operator">::</span>next()
{
<span class="type"><a href="qstring.html">QString</a></span> name <span class="operator">=</span> nameLine<span class="operator">-</span><span class="operator">></span>text();
<span class="type"><a href="qmap.html">QMap</a></span><span class="operator"><</span><span class="type"><a href="qstring.html">QString</a></span><span class="operator">,</span> <span class="type"><a href="qstring.html">QString</a></span><span class="operator">></span><span class="operator">::</span>iterator i <span class="operator">=</span> contacts<span class="operator">.</span>find(name);
<span class="keyword">if</span> (i <span class="operator">!</span><span class="operator">=</span> contacts<span class="operator">.</span>end())
i<span class="operator">+</span><span class="operator">+</span>;
<span class="keyword">if</span> (i <span class="operator">=</span><span class="operator">=</span> contacts<span class="operator">.</span>end())
i <span class="operator">=</span> contacts<span class="operator">.</span>begin();
nameLine<span class="operator">-</span><span class="operator">></span>setText(i<span class="operator">.</span>key());
addressText<span class="operator">-</span><span class="operator">></span>setText(i<span class="operator">.</span>value());
}</pre>
<p>Une fois que nous avons itéré jusqu'à l'objet recherché dans <tt>contacts</tt>, nous affichons son contenu sur <tt>nameLine</tt> et <tt>addressText</tt>.</p>
<p>De la même façon, pour la méthode <tt>previous()</tt>, nous obtenons un itérateur sur <tt>contacts</tt> et ensuite:</p>
<ul>
<li>Si l'itérateur est à la fin de <tt>contacts</tt>, on réinitialise l'affichage et on retourne.</li>
<li>Si l'itérateur est au début de <tt>contacts</tt>, on change sa position jusqu'à la fin</li>
<li>Ensuite, on décrémente l'itérateur</li>
</ul>
<pre class="cpp"> <span class="type">void</span> AddressBook<span class="operator">::</span>previous()
{
<span class="type"><a href="qstring.html">QString</a></span> name <span class="operator">=</span> nameLine<span class="operator">-</span><span class="operator">></span>text();
<span class="type"><a href="qmap.html">QMap</a></span><span class="operator"><</span><span class="type"><a href="qstring.html">QString</a></span><span class="operator">,</span> <span class="type"><a href="qstring.html">QString</a></span><span class="operator">></span><span class="operator">::</span>iterator i <span class="operator">=</span> contacts<span class="operator">.</span>find(name);
<span class="keyword">if</span> (i <span class="operator">=</span><span class="operator">=</span> contacts<span class="operator">.</span>end()){
nameLine<span class="operator">-</span><span class="operator">></span>clear();
addressText<span class="operator">-</span><span class="operator">></span>clear();
<span class="keyword">return</span>;
}
<span class="keyword">if</span> (i <span class="operator">=</span><span class="operator">=</span> contacts<span class="operator">.</span>begin())
i <span class="operator">=</span> contacts<span class="operator">.</span>end();
i<span class="operator">-</span><span class="operator">-</span>;
nameLine<span class="operator">-</span><span class="operator">></span>setText(i<span class="operator">.</span>key());
addressText<span class="operator">-</span><span class="operator">></span>setText(i<span class="operator">.</span>value());
}</pre>
<p>à nouveau, nous affichons le contenu de l'objet courant dans <tt>contacts</tt>.</p>
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