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<h3><a name="toc">Contents</a></h3>
<ul>
<li class="level1"><a href="#ftpwindow-class-definition">FtpWindow Class Definition</a></li>
<li class="level1"><a href="#ftpwindow-class-implementation">FtpWindow Class Implementation</a></li>
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<h1 class="title">FTP Example</h1>
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<p>Files:</p>
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<li><a href="network-qftp-ftpwindow-cpp.html">network/qftp/ftpwindow.cpp</a></li>
<li><a href="network-qftp-ftpwindow-h.html">network/qftp/ftpwindow.h</a></li>
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<p>The FTP example demonstrates a simple FTP client that can be used to list the available files on an FTP server and download them.<p class="centerAlign"><img src="images/ftp-example.png" alt="" /></p><p>The user of the example can enter the address or hostname of an FTP server in the <b>Ftp Server</b> line edit, and then push the <b>Connect</b> button to connect to it. A list of the server's top-level directory is then presented in the <b>File List</b> tree view. If the selected item in the view is a file, the user can download it by pushing the <b>Download</b> button. An item representing a directory can be double clicked with the mouse to show the contents of that directory in the view.</p>
<p>The functionality required for the example is implemented in the <a href="qftp.html">QFtp</a> class, which provides an easy, high-level interface to the file transfer protocol. FTP operations are requested through <a href="qftp.html#Command-enum">QFtp::Command</a>s. The operations are asynchronous. <a href="qftp.html">QFtp</a> will notify us through signals when commands are started and finished.</p>
<p>We have one class, <tt>FtpWindow</tt>, which sets up the GUI and handles the FTP functionality. We will now go through its definition and implementation - focusing on the code concerning FTP. The code for managing the GUI is explained in other examples.</p>
<a name="ftpwindow-class-definition"></a>
<h2>FtpWindow Class Definition</h2>
<p>The <tt>FtpWindow</tt> class displays a window, in which the user can connect to and browse the contents of an FTP server. The slots of <tt>FtpWindow</tt> are connected to its widgets, and contain the functionality for managing the FTP connection. We also connect to signals in <a href="qftp.html">QFtp</a>, which tells us when the <a href="qftp.html#Command-enum">commands</a> we request are finished, the progress of current commands, and information about files on the server.</p>
<pre class="cpp"> <span class="keyword">private</span> <span class="keyword">slots</span>:
<span class="type">void</span> connectOrDisconnect();
<span class="type">void</span> downloadFile();
<span class="type">void</span> cancelDownload();
<span class="type">void</span> connectToFtp();
<span class="type">void</span> ftpCommandFinished(<span class="type">int</span> commandId<span class="operator">,</span> <span class="type">bool</span> error);
<span class="type">void</span> addToList(<span class="keyword">const</span> <span class="type"><a href="qurlinfo.html">QUrlInfo</a></span> <span class="operator">&</span>urlInfo);
<span class="type">void</span> processItem(<span class="type"><a href="qtreewidgetitem.html">QTreeWidgetItem</a></span> <span class="operator">*</span>item<span class="operator">,</span> <span class="type">int</span> column);
<span class="type">void</span> cdToParent();
<span class="type">void</span> updateDataTransferProgress(<span class="type"><a href="qtglobal.html#qint64-typedef">qint64</a></span> readBytes<span class="operator">,</span>
<span class="type"><a href="qtglobal.html#qint64-typedef">qint64</a></span> totalBytes);
<span class="type">void</span> enableDownloadButton();
<span class="type">void</span> enableConnectButton();</pre>
<p>We will look at each slot when we examine the <tt>FtpWindow</tt> implementation in the next section. We also make use of a few private variables:</p>
<pre class="cpp"> <span class="type"><a href="qhash.html">QHash</a></span><span class="operator"><</span><span class="type"><a href="qstring.html">QString</a></span><span class="operator">,</span> <span class="type">bool</span><span class="operator">></span> isDirectory;
<span class="type"><a href="qstring.html">QString</a></span> currentPath;
<span class="type"><a href="qftp.html">QFtp</a></span> <span class="operator">*</span>ftp;
<span class="type"><a href="qfile.html">QFile</a></span> <span class="operator">*</span>file;
<span class="type"><a href="qnetworksession.html">QNetworkSession</a></span> <span class="operator">*</span>networkSession;
<span class="type"><a href="qnetworkconfigurationmanager.html">QNetworkConfigurationManager</a></span> manager;</pre>
<p>The <tt>isDirectory</tt> hash keeps a history of all entries explored on the FTP server, and registers whether an entry represents a directory or a file. We use the <a href="qfile.html">QFile</a> object to download files from the FTP server.</p>
<a name="ftpwindow-class-implementation"></a>
<h2>FtpWindow Class Implementation</h2>
<p>We skip the <tt>FtpWindow</tt> constructor as it only contains code for setting up the GUI, which is explained in other examples.</p>
<p>We move on to the slots, starting with <tt>connectOrDisconnect()</tt>.</p>
<pre class="cpp"> <span class="type">void</span> FtpWindow<span class="operator">::</span>connectOrDisconnect()
{
<span class="keyword">if</span> (ftp) {
ftp<span class="operator">-</span><span class="operator">></span>abort();
ftp<span class="operator">-</span><span class="operator">></span>deleteLater();
ftp <span class="operator">=</span> <span class="number">0</span>;</pre>
<p>If <tt>ftp</tt> is already pointing to a <a href="qftp.html">QFtp</a> object, we <a href="qftp.html#Command-enum">QFtp::Close</a> its FTP connection and delete the object it points to. Note that we do not delete the object using standard C++ <tt>delete</tt> as we need it to finish its abort operation.</p>
<pre class="qml"> ...
ftp <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="qftp.html">QFtp</a></span>(<span class="keyword">this</span>);
connect(ftp<span class="operator">,</span> SIGNAL(commandFinished(<span class="type">int</span><span class="operator">,</span><span class="type">bool</span>))<span class="operator">,</span>
<span class="keyword">this</span><span class="operator">,</span> SLOT(ftpCommandFinished(<span class="type">int</span><span class="operator">,</span><span class="type">bool</span>)));
connect(ftp<span class="operator">,</span> SIGNAL(listInfo(<span class="type"><a href="qurlinfo.html">QUrlInfo</a></span>))<span class="operator">,</span>
<span class="keyword">this</span><span class="operator">,</span> SLOT(addToList(<span class="type"><a href="qurlinfo.html">QUrlInfo</a></span>)));
connect(ftp<span class="operator">,</span> SIGNAL(dataTransferProgress(<span class="type"><a href="qtglobal.html#qint64-typedef">qint64</a></span><span class="operator">,</span><span class="type"><a href="qtglobal.html#qint64-typedef">qint64</a></span>))<span class="operator">,</span>
<span class="keyword">this</span><span class="operator">,</span> SLOT(updateDataTransferProgress(<span class="type"><a href="qtglobal.html#qint64-typedef">qint64</a></span><span class="operator">,</span><span class="type"><a href="qtglobal.html#qint64-typedef">qint64</a></span>)));
fileList<span class="operator">-</span><span class="operator">></span>clear();
currentPath<span class="operator">.</span>clear();
isDirectory<span class="operator">.</span>clear();</pre>
<p>If we get here, <tt>connectOrDisconnect()</tt> was called to establish a new FTP connection. We create a new <a href="qftp.html">QFtp</a> for our new connection, and connect its signals to slots in <tt>FtpWindow</tt>. The <a href="qftp.html#listInfo">listInfo()</a> signal is emitted whenever information about a single file on the sever has been resolved. This signal is sent when we ask <a href="qftp.html">QFtp</a> to <a href="qftp.html#list">list()</a> the contents of a directory. Finally, the <a href="qftp.html#dataTransferProgress">dataTransferProgress()</a> signal is emitted repeatedly during an FTP file transfer, giving us progress reports.</p>
<pre class="cpp"> <span class="type"><a href="qurl.html">QUrl</a></span> url(ftpServerLineEdit<span class="operator">-</span><span class="operator">></span>text());
<span class="keyword">if</span> (<span class="operator">!</span>url<span class="operator">.</span>isValid() <span class="operator">|</span><span class="operator">|</span> url<span class="operator">.</span>scheme()<span class="operator">.</span>toLower() <span class="operator">!</span><span class="operator">=</span> QLatin1String(<span class="string">"ftp"</span>)) {
ftp<span class="operator">-</span><span class="operator">></span>connectToHost(ftpServerLineEdit<span class="operator">-</span><span class="operator">></span>text()<span class="operator">,</span> <span class="number">21</span>);
ftp<span class="operator">-</span><span class="operator">></span>login();
} <span class="keyword">else</span> {
ftp<span class="operator">-</span><span class="operator">></span>connectToHost(url<span class="operator">.</span>host()<span class="operator">,</span> url<span class="operator">.</span>port(<span class="number">21</span>));
<span class="keyword">if</span> (<span class="operator">!</span>url<span class="operator">.</span>userName()<span class="operator">.</span>isEmpty())
ftp<span class="operator">-</span><span class="operator">></span>login(<span class="type"><a href="qurl.html">QUrl</a></span><span class="operator">::</span>fromPercentEncoding(url<span class="operator">.</span>userName()<span class="operator">.</span>toLatin1())<span class="operator">,</span> url<span class="operator">.</span>password());
<span class="keyword">else</span>
ftp<span class="operator">-</span><span class="operator">></span>login();
<span class="keyword">if</span> (<span class="operator">!</span>url<span class="operator">.</span>path()<span class="operator">.</span>isEmpty())
ftp<span class="operator">-</span><span class="operator">></span>cd(url<span class="operator">.</span>path());
}</pre>
<p>The <b>Ftp Server</b> line edit contains the IP address or hostname of the server to which we want to connect. We first check that the URL is a valid FTP sever address. If it isn't, we still try to connect using the plain text in <tt>ftpServerLineEdit</tt>. In either case, we assume that port <tt>21</tt> is used.</p>
<p>If the URL does not contain a user name and password, we use <a href="qftp.html#login">QFtp::login</a>(), which will attempt to log into the FTP sever as an anonymous user. The <a href="qftp.html">QFtp</a> object will now notify us when it has connected to the FTP server; it will also send a signal if it fails to connect or the username and password were rejected.</p>
<p>We move on to the <tt>downloadFile()</tt> slot:</p>
<pre class="cpp"> <span class="type">void</span> FtpWindow<span class="operator">::</span>downloadFile()
{
<span class="type"><a href="qstring.html">QString</a></span> fileName <span class="operator">=</span> fileList<span class="operator">-</span><span class="operator">></span>currentItem()<span class="operator">-</span><span class="operator">></span>text(<span class="number">0</span>);
...
file <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="qfile.html">QFile</a></span>(fileName);
<span class="keyword">if</span> (<span class="operator">!</span>file<span class="operator">-</span><span class="operator">></span>open(<span class="type"><a href="qiodevice.html">QIODevice</a></span><span class="operator">::</span>WriteOnly)) {
<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">"FTP"</span>)<span class="operator">,</span>
tr(<span class="string">"Unable to save the file %1: %2."</span>)
<span class="operator">.</span>arg(fileName)<span class="operator">.</span>arg(file<span class="operator">-</span><span class="operator">></span>errorString()));
<span class="keyword">delete</span> file;
<span class="keyword">return</span>;
}
ftp<span class="operator">-</span><span class="operator">></span>get(fileList<span class="operator">-</span><span class="operator">></span>currentItem()<span class="operator">-</span><span class="operator">></span>text(<span class="number">0</span>)<span class="operator">,</span> file);
progressDialog<span class="operator">-</span><span class="operator">></span>setLabelText(tr(<span class="string">"Downloading %1..."</span>)<span class="operator">.</span>arg(fileName));
downloadButton<span class="operator">-</span><span class="operator">></span>setEnabled(<span class="keyword">false</span>);
progressDialog<span class="operator">-</span><span class="operator">></span>exec();
}</pre>
<p>We first fetch the name of the file, which we find in the selected item of <tt>fileList</tt>. We then start the download by using <a href="qftp.html#get">QFtp::get</a>(). <a href="qftp.html">QFtp</a> will send progress signals during the download and a signal when the download is completed.</p>
<pre class="cpp"> <span class="type">void</span> FtpWindow<span class="operator">::</span>cancelDownload()
{
ftp<span class="operator">-</span><span class="operator">></span>abort();
<span class="keyword">if</span> (file<span class="operator">-</span><span class="operator">></span>exists()) {
file<span class="operator">-</span><span class="operator">></span>close();
file<span class="operator">-</span><span class="operator">></span>remove();
}
<span class="keyword">delete</span> file;
}</pre>
<p><a href="qftp.html">QFtp</a> supports canceling the download of files. We make sure that any file that is currently being written to is closed and removed, and tidy up by deleting the file object.</p>
<pre class="cpp"> <span class="type">void</span> FtpWindow<span class="operator">::</span>ftpCommandFinished(<span class="type">int</span><span class="operator">,</span> <span class="type">bool</span> error)
{
<span class="preprocessor">#ifndef QT_NO_CURSOR</span>
setCursor(<span class="type"><a href="qt.html">Qt</a></span><span class="operator">::</span>ArrowCursor);
<span class="preprocessor">#endif</span>
<span class="keyword">if</span> (ftp<span class="operator">-</span><span class="operator">></span>currentCommand() <span class="operator">=</span><span class="operator">=</span> <span class="type"><a href="qftp.html">QFtp</a></span><span class="operator">::</span>ConnectToHost) {
<span class="keyword">if</span> (error) {
<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">"FTP"</span>)<span class="operator">,</span>
tr(<span class="string">"Unable to connect to the FTP server "</span>
<span class="string">"at %1. Please check that the host "</span>
<span class="string">"name is correct."</span>)
<span class="operator">.</span>arg(ftpServerLineEdit<span class="operator">-</span><span class="operator">></span>text()));
connectOrDisconnect();
<span class="keyword">return</span>;
}
statusLabel<span class="operator">-</span><span class="operator">></span>setText(tr(<span class="string">"Logged onto %1."</span>)
<span class="operator">.</span>arg(ftpServerLineEdit<span class="operator">-</span><span class="operator">></span>text()));
fileList<span class="operator">-</span><span class="operator">></span>setFocus();
downloadButton<span class="operator">-</span><span class="operator">></span>setDefault(<span class="keyword">true</span>);
connectButton<span class="operator">-</span><span class="operator">></span>setEnabled(<span class="keyword">true</span>);
<span class="keyword">return</span>;
}</pre>
<p>The <tt>ftpCommandFinished()</tt> slot is called when <a href="qftp.html">QFtp</a> has finished a <a href="qftp.html#Command-enum">QFtp::Command</a>. If an error occurred during the command, <a href="qftp.html">QFtp</a> will set <tt>error</tt> to one of the values in the <a href="qftp.html#Error-enum">QFtp::Error</a> enum; otherwise, <tt>error</tt> is zero.</p>
<pre class="cpp"> <span class="keyword">if</span> (ftp<span class="operator">-</span><span class="operator">></span>currentCommand() <span class="operator">=</span><span class="operator">=</span> <span class="type"><a href="qftp.html">QFtp</a></span><span class="operator">::</span>Login)
ftp<span class="operator">-</span><span class="operator">></span>list();</pre>
<p>After login, the <a href="qftp.html#list">QFtp::list</a>() function will list the top-level directory on the server. addToList() is connected to <a href="qftp.html#listInfo">QFtp::listInfo</a>(), and will be invoked for each entry in that directory.</p>
<pre class="cpp"> <span class="keyword">if</span> (ftp<span class="operator">-</span><span class="operator">></span>currentCommand() <span class="operator">=</span><span class="operator">=</span> <span class="type"><a href="qftp.html">QFtp</a></span><span class="operator">::</span>Get) {
<span class="keyword">if</span> (error) {
statusLabel<span class="operator">-</span><span class="operator">></span>setText(tr(<span class="string">"Canceled download of %1."</span>)
<span class="operator">.</span>arg(file<span class="operator">-</span><span class="operator">></span>fileName()));
file<span class="operator">-</span><span class="operator">></span>close();
file<span class="operator">-</span><span class="operator">></span>remove();
} <span class="keyword">else</span> {
statusLabel<span class="operator">-</span><span class="operator">></span>setText(tr(<span class="string">"Downloaded %1 to current directory."</span>)
<span class="operator">.</span>arg(file<span class="operator">-</span><span class="operator">></span>fileName()));
file<span class="operator">-</span><span class="operator">></span>close();
}
<span class="keyword">delete</span> file;
enableDownloadButton();
progressDialog<span class="operator">-</span><span class="operator">></span>hide();</pre>
<p>When a <a href="qftp.html#Command-enum">Get</a> command is finished, a file has finished downloading (or an error occurred during the download).</p>
<pre class="cpp"> } <span class="keyword">else</span> <span class="keyword">if</span> (ftp<span class="operator">-</span><span class="operator">></span>currentCommand() <span class="operator">=</span><span class="operator">=</span> <span class="type"><a href="qftp.html">QFtp</a></span><span class="operator">::</span>List) {
<span class="keyword">if</span> (isDirectory<span class="operator">.</span>isEmpty()) {
fileList<span class="operator">-</span><span class="operator">></span>addTopLevelItem(<span class="keyword">new</span> <span class="type"><a href="qtreewidgetitem.html">QTreeWidgetItem</a></span>(<span class="type"><a href="qstringlist.html">QStringList</a></span>() <span class="operator"><</span><span class="operator"><</span> tr(<span class="string">"<empty>"</span>)));
fileList<span class="operator">-</span><span class="operator">></span>setEnabled(<span class="keyword">false</span>);
}
}</pre>
<p>After a <a href="qftp.html#Command-enum">List</a> command is performed, we have to check if no entries were found (in which case our <tt>addToList()</tt> function would not have been called).</p>
<p>Let's continue with the <tt>addToList()</tt> slot:</p>
<pre class="cpp"> <span class="type">void</span> FtpWindow<span class="operator">::</span>addToList(<span class="keyword">const</span> <span class="type"><a href="qurlinfo.html">QUrlInfo</a></span> <span class="operator">&</span>urlInfo)
{
<span class="type"><a href="qtreewidgetitem.html">QTreeWidgetItem</a></span> <span class="operator">*</span>item <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="qtreewidgetitem.html">QTreeWidgetItem</a></span>;
item<span class="operator">-</span><span class="operator">></span>setText(<span class="number">0</span><span class="operator">,</span> urlInfo<span class="operator">.</span>name());
item<span class="operator">-</span><span class="operator">></span>setText(<span class="number">1</span><span class="operator">,</span> <span class="type"><a href="qstring.html">QString</a></span><span class="operator">::</span>number(urlInfo<span class="operator">.</span>size()));
item<span class="operator">-</span><span class="operator">></span>setText(<span class="number">2</span><span class="operator">,</span> urlInfo<span class="operator">.</span>owner());
item<span class="operator">-</span><span class="operator">></span>setText(<span class="number">3</span><span class="operator">,</span> urlInfo<span class="operator">.</span>group());
item<span class="operator">-</span><span class="operator">></span>setText(<span class="number">4</span><span class="operator">,</span> urlInfo<span class="operator">.</span>lastModified()<span class="operator">.</span>toString(<span class="string">"MMM dd yyyy"</span>));
<span class="type"><a href="qpixmap.html">QPixmap</a></span> pixmap(urlInfo<span class="operator">.</span>isDir() <span class="operator">?</span> <span class="string">":/images/dir.png"</span> : <span class="string">":/images/file.png"</span>);
item<span class="operator">-</span><span class="operator">></span>setIcon(<span class="number">0</span><span class="operator">,</span> pixmap);
isDirectory<span class="operator">[</span>urlInfo<span class="operator">.</span>name()<span class="operator">]</span> <span class="operator">=</span> urlInfo<span class="operator">.</span>isDir();
fileList<span class="operator">-</span><span class="operator">></span>addTopLevelItem(item);
<span class="keyword">if</span> (<span class="operator">!</span>fileList<span class="operator">-</span><span class="operator">></span>currentItem()) {
fileList<span class="operator">-</span><span class="operator">></span>setCurrentItem(fileList<span class="operator">-</span><span class="operator">></span>topLevelItem(<span class="number">0</span>));
fileList<span class="operator">-</span><span class="operator">></span>setEnabled(<span class="keyword">true</span>);
}
}</pre>
<p>When a new file has been resolved during a <a href="qftp.html#Command-enum">QFtp::List</a> command, this slot is invoked with a <a href="qurlinfo.html">QUrlInfo</a> describing the file. We create a separate row for the file in <tt>fileList</tt>. If <tt>fileList</tt> does not have a current item, we set the new item to be the current item.</p>
<pre class="cpp"> <span class="type">void</span> FtpWindow<span class="operator">::</span>processItem(<span class="type"><a href="qtreewidgetitem.html">QTreeWidgetItem</a></span> <span class="operator">*</span>item<span class="operator">,</span> <span class="type">int</span> <span class="comment">/*column*/</span>)
{
<span class="type"><a href="qstring.html">QString</a></span> name <span class="operator">=</span> item<span class="operator">-</span><span class="operator">></span>text(<span class="number">0</span>);
<span class="keyword">if</span> (isDirectory<span class="operator">.</span>value(name)) {
fileList<span class="operator">-</span><span class="operator">></span>clear();
isDirectory<span class="operator">.</span>clear();
currentPath <span class="operator">+</span><span class="operator">=</span> <span class="char">'/'</span>;
currentPath <span class="operator">+</span><span class="operator">=</span> name;
ftp<span class="operator">-</span><span class="operator">></span>cd(name);
ftp<span class="operator">-</span><span class="operator">></span>list();
cdToParentButton<span class="operator">-</span><span class="operator">></span>setEnabled(<span class="keyword">true</span>);
<span class="preprocessor">#ifndef QT_NO_CURSOR</span>
setCursor(<span class="type"><a href="qt.html">Qt</a></span><span class="operator">::</span>WaitCursor);
<span class="preprocessor">#endif</span>
<span class="keyword">return</span>;
}
}</pre>
<p>The <tt>processItem()</tt> slot is called when an item is double clicked in the <b>File List</b>. If the item represents a directory, we want to load the contents of that directory with <a href="qftp.html#list">QFtp::list</a>().</p>
<pre class="cpp"> <span class="type">void</span> FtpWindow<span class="operator">::</span>cdToParent()
{
<span class="preprocessor">#ifndef QT_NO_CURSOR</span>
setCursor(<span class="type"><a href="qt.html">Qt</a></span><span class="operator">::</span>WaitCursor);
<span class="preprocessor">#endif</span>
fileList<span class="operator">-</span><span class="operator">></span>clear();
isDirectory<span class="operator">.</span>clear();
currentPath <span class="operator">=</span> currentPath<span class="operator">.</span>left(currentPath<span class="operator">.</span>lastIndexOf(<span class="char">'/'</span>));
<span class="keyword">if</span> (currentPath<span class="operator">.</span>isEmpty()) {
cdToParentButton<span class="operator">-</span><span class="operator">></span>setEnabled(<span class="keyword">false</span>);
ftp<span class="operator">-</span><span class="operator">></span>cd(<span class="string">"/"</span>);
} <span class="keyword">else</span> {
ftp<span class="operator">-</span><span class="operator">></span>cd(currentPath);
}
ftp<span class="operator">-</span><span class="operator">></span>list();
}</pre>
<p><tt>cdToParent()</tt> is invoked when the user requests to go to the parent directory of the one displayed in the file list. After changing the directory, we <a href="qftp.html#Command-enum">QFtp::List</a> its contents.</p>
<pre class="cpp"> <span class="type">void</span> FtpWindow<span class="operator">::</span>updateDataTransferProgress(<span class="type"><a href="qtglobal.html#qint64-typedef">qint64</a></span> readBytes<span class="operator">,</span>
<span class="type"><a href="qtglobal.html#qint64-typedef">qint64</a></span> totalBytes)
{
progressDialog<span class="operator">-</span><span class="operator">></span>setMaximum(totalBytes);
progressDialog<span class="operator">-</span><span class="operator">></span>setValue(readBytes);
}</pre>
<p>The <tt>updateDataTransferProgress()</tt> slot is called regularly by <a href="qftp.html#dataTransferProgress">QFtp::dataTransferProgress</a>() when a file download is in progress. We use a <a href="qprogressdialog.html">QProgressDialog</a> to show the download progression to the user.</p>
<pre class="cpp"> <span class="type">void</span> FtpWindow<span class="operator">::</span>enableDownloadButton()
{
<span class="type"><a href="qtreewidgetitem.html">QTreeWidgetItem</a></span> <span class="operator">*</span>current <span class="operator">=</span> fileList<span class="operator">-</span><span class="operator">></span>currentItem();
<span class="keyword">if</span> (current) {
<span class="type"><a href="qstring.html">QString</a></span> currentFile <span class="operator">=</span> current<span class="operator">-</span><span class="operator">></span>text(<span class="number">0</span>);
downloadButton<span class="operator">-</span><span class="operator">></span>setEnabled(<span class="operator">!</span>isDirectory<span class="operator">.</span>value(currentFile));
} <span class="keyword">else</span> {
downloadButton<span class="operator">-</span><span class="operator">></span>setEnabled(<span class="keyword">false</span>);
}
}</pre>
<p>The <tt>enableDownloadButton()</tt> is called whenever the current item in <tt>fileList</tt> changes. If the item represents a file, the <b>Enable Download</b> Button should be enabled; otherwise, it is disabled.</p>
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