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<?xml version="1.0" encoding="iso-8859-1"?>
<!DOCTYPE html
PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<!-- loader.qdoc -->
<head>
<title>Loading Documents</title>
<link href="classic.css" rel="stylesheet" type="text/css" />
</head>
<body>
<table border="0" cellpadding="0" cellspacing="0" width="100%">
<tr>
<td align="left" valign="top" width="32"><img src="images/qt-logo.png" align="left" width="57" height="67" border="0" /></td>
<td width="1"> </td><td class="postheader" valign="center"><a href="index.html"><font color="#004faf">Home</font></a></td>
</tr></table><h1 class="title">Loading Documents<br /><span class="subtitle"></span>
</h1>
<p>The application in this example loads or prints the documents passed as commandline parameters to further instances of this application.</p>
<pre><span class="comment"> /****************************************************************************
**
** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
** All rights reserved.
**
** Contact: Nokia Corporation (qt-info@nokia.com)
**
** This file is part of a Qt Solutions component.
**
** You may use this file under the terms of the BSD license as follows:
**
** "Redistribution and use in source and binary forms, with or without
** modification, are permitted provided that the following conditions are
** met:
** * Redistributions of source code must retain the above copyright
** notice, this list of conditions and the following disclaimer.
** * Redistributions in binary form must reproduce the above copyright
** notice, this list of conditions and the following disclaimer in
** the documentation and/or other materials provided with the
** distribution.
** * Neither the name of Nokia Corporation and its Subsidiary(-ies) nor
** the names of its contributors may be used to endorse or promote
** products derived from this software without specific prior written
** permission.
**
** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
**
****************************************************************************/</span>
#include <qtsingleapplication.h>
#include <QtCore/QFile>
#include <QtGui/QMainWindow>
#include <QtGui/QPrinter>
#include <QtGui/QPainter>
#include <QtGui/QTextEdit>
#include <QtGui/QMdiArea>
#include <QtCore/QTextStream>
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
MainWindow();
public slots:
void handleMessage(const QString& message);
signals:
void needToShow();
private:
QMdiArea *workspace;
};</pre>
<p>The user interface in this application is a <a href="http://qt.nokia.com/doc/4.6/qmainwindow.html">QMainWindow</a> subclass with a <a href="http://qt.nokia.com/doc/4.6/qmdiarea.html">QMdiArea</a> as the central widget. It implements a slot <tt>handleMessage()</tt> that will be connected to the messageReceived() signal of the <a href="qtsingleapplication.html">QtSingleApplication</a> class.</p>
<pre> MainWindow::MainWindow()
{
workspace = new QMdiArea(this);
setCentralWidget(workspace);
}</pre>
<p>The <a href="http://qt.nokia.com/doc/4.6/designer-to-know.html">MainWindow</a> constructor creates a minimal user interface.</p>
<pre> void MainWindow::handleMessage(const QString& message)
{
enum Action {
Nothing,
Open,
Print
} action;
action = Nothing;
QString filename = message;
if (message.toLower().startsWith("/print ")) {
filename = filename.mid(7);
action = Print;
} else if (!message.isEmpty()) {
action = Open;
}
if (action == Nothing) {
emit needToShow();
return;
}
QFile file(filename);
QString contents;
if (file.open(QIODevice::ReadOnly))
contents = file.readAll();
else
contents = "[[Error: Could not load file " + filename + "]]";
QTextEdit *view = new QTextEdit;
view->setPlainText(contents);
switch(action) {</pre>
<p>The handleMessage() slot interprets the message passed in as a filename that can be prepended with <i>/print</i> to indicate that the file should just be printed rather than loaded.</p>
<pre> case Print:
{
QPrinter printer;
view->print(&printer);
delete view;
}
break;
case Open:
{
workspace->addSubWindow(view);
view->setWindowTitle(message);
view->show();
emit needToShow();
}
break;
default:
break;
};
}</pre>
<p>Loading the file will also activate the window.</p>
<pre> #include "main.moc"
int main(int argc, char **argv)
{
QtSingleApplication instance("File loader QtSingleApplication example", argc, argv);
QString message;
for (int a = 1; a < argc; ++a) {
message += argv[a];
if (a < argc-1)
message += " ";
}
if (instance.sendMessage(message))
return 0;</pre>
<p>The <tt>main</tt> entry point function creates a <a href="qtsingleapplication.html">QtSingleApplication</a> object, and creates a message to send to a running instance of the application. If the message was sent successfully the process exits immediately.</p>
<pre> MainWindow mw;
mw.handleMessage(message);
mw.show();
QObject::connect(&instance, SIGNAL(messageReceived(const QString&)),
&mw, SLOT(handleMessage(const QString&)));
instance.setActivationWindow(&mw, false);
QObject::connect(&mw, SIGNAL(needToShow()), &instance, SLOT(activateWindow()));
return instance.exec();
}</pre>
<p>If the message could not be sent the application starts up. Note that <tt>false</tt> is passed to the call to setActivationWindow() to prevent automatic activation for every message received, e.g. when the application should just print a file. Instead, the message handling function determines whether activation is requested, and signals that by emitting the needToShow() signal. This is then simply connected directly to <a href="qtsingleapplication.html">QtSingleApplication</a>'s activateWindow() slot.</p>
<p /><address><hr /><div align="center">
<table width="100%" cellspacing="0" border="0"><tr class="address">
<td width="30%" align="left">Copyright © 2010 Nokia Corporation and/or its subsidiary(-ies)</td>
<td width="40%" align="center"><a href="http://qt.nokia.com/doc/trademarks.html">Trademarks</a></td>
<td width="30%" align="right"><div align="right">Qt Solutions</div></td>
</tr></table></div></address></body>
</html>
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