C++/Qt/QEvent
Extend QObject to create keyboard filter
<source lang="cpp"> Foundations of Qt Development\Chapter06\eventfilter\main.cpp /*
* Copyright (c) 2006-2007, Johan Thelin * * All rights reserved. * * 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 APress 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. * */
- include <QApplication>
- include <QLineEdit>
- include <QKeyEvent>
class KeyboardFilter : public QObject { public:
KeyboardFilter( QObject *parent = 0 ) : QObject( parent ) {}
protected:
bool eventFilter( QObject *dist, QEvent *event ) { if( event->type() == QEvent::KeyPress ) { QKeyEvent *keyEvent = static_cast<QKeyEvent*>( event ); if( QString("1234567890").indexOf( keyEvent->text() ) != -1 ) return true; } return false; }
}; int main( int argc, char **argv ) {
QApplication app( argc, argv ); QLineEdit lineEdit; KeyboardFilter filter; lineEdit.installEventFilter( &filter ); lineEdit.show(); return app.exec();
}
</source>
Subclass QEvent
<source lang="cpp"> /****************************************************************************
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- Contact: Nokia Corporation (qt-info@nokia.com)
- This file is part of the documentation of the Qt Toolkit.
- $QT_BEGIN_LICENSE:LGPL$
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- Licensees holding valid Qt Commercial licenses may use this file in
- accordance with the Qt Commercial License Agreement provided with the
- Software or, alternatively, in accordance with the terms contained in
- a written agreement between you and Nokia.
- GNU Lesser General Public License Usage
- Alternatively, this file may be used under the terms of the GNU Lesser
- General Public License version 2.1 as published by the Free Software
- Foundation and appearing in the file LICENSE.LGPL included in the
- packaging of this file. Please review the following information to
- ensure the GNU Lesser General Public License version 2.1 requirements
- will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
- In addition, as a special exception, Nokia gives you certain additional
- rights. These rights are described in the Nokia Qt LGPL Exception
- version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
- GNU General Public License Usage
- Alternatively, this file may be used under the terms of the GNU
- General Public License version 3.0 as published by the Free Software
- Foundation and appearing in the file LICENSE.GPL included in the
- packaging of this file. Please review the following information to
- ensure the GNU General Public License version 3.0 requirements will be
- met: http://www.gnu.org/copyleft/gpl.html.
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- /
- include <QCheckBox>
- include <QMouseEvent>
class MyCheckBox : public QCheckBox { public:
void mousePressEvent(QMouseEvent *event);
}; void MyCheckBox::mousePressEvent(QMouseEvent *event) {
if (event->button() == Qt::LeftButton) { // handle left mouse button here } else { // pass on other buttons to base class QCheckBox::mousePressEvent(event); }
} class MyWidget : public QWidget { public:
bool event(QEvent *event);
}; static const int MyCustomEventType = 1099; class MyCustomEvent : public QEvent { public:
MyCustomEvent() : QEvent((QEvent::Type)MyCustomEventType) {}
}; bool MyWidget::event(QEvent *event) {
if (event->type() == QEvent::KeyPress) { QKeyEvent *ke = static_cast<QKeyEvent *>(event); if (ke->key() == Qt::Key_Tab) { return true; } } else if (event->type() == MyCustomEventType) { MyCustomEvent *myEvent = static_cast<MyCustomEvent *>(event); return true; } return QWidget::event(event);
} int main() { }
</source>