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Revision as of 09:48, 5 March 2012 by hamishwillee (Talk | contribs)

How to use QCompass sensor

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This code snippet shows how to use Qt's QCompass sensor and display sensor data on the screen.

Article Metadata
Code ExampleTested with
Devices(s): N8,C7,E7
Compatibility
Platform(s): Symbian
Symbian
Article
Keywords: QCompass,Qt Mobility ,Sensor API
Created: chintandave_er (29 Nov 2010)
Last edited: hamishwillee (05 Mar 2012)

Contents

Project File (.pro file)

  • Add the Qt Mobility project configuration option in the .Pro file as shown below
CONFIG += mobility
MOBILITY += sensors
  • here is the full project(.pro) file.
QT       += core gui
 
TARGET = QtCompasSensor
TEMPLATE = app
 
 
SOURCES += main.cpp\
qtcompassensor.cpp
 
HEADERS += qtcompassensor.h
 
CONFIG += mobility
CONFIG += debug
MOBILITY = sensors
 
symbian {
TARGET.UID3 = 0xe00fb3c0
# TARGET.CAPABILITY +=
TARGET.EPOCSTACKSIZE = 0x14000
TARGET.EPOCHEAPSIZE = 0x020000 0x800000
}


Header

  • Add the Qt Mobility namespace to use Qt Mobiltiy in header file
QTM_USE_NAMESPACE

Here is the qtcompassensor.h header file.

#include <QtGui/QMainWindow>
#include <QGraphicsView>
#include <QBasicTimer>
#include <QTimer>
#include <QCompass> // Add Sensor Class
 
// add Qt Mobility Project Namespace
QTM_USE_NAMESPACE
 
class QGraphicsRectItem;
class QGraphicsSimpleTextItem;
 
class QtCompasSensor : public QGraphicsView
{
Q_OBJECT
 
public:
QtCompasSensor(QWidget *parent = 0);
 
protected:
bool event(QEvent *event);
 
private:
void updateCompasSensor();
 
private:
QGraphicsRectItem *Rect;
QGraphicsSimpleTextItem *text;
QCompass *CompasSensor;
QBasicTimer Timer;
QTimer inactiveTimer;
};


Source

Here is the qtcompassensor.cpp source file.

#include "qtcompassensor.h"
#include <QGraphicsRectItem>
#include <QGraphicsSimpleTextItem>
#include <QResizeEvent>
 
// include timer event
#include <QTimerEvent>
#include <QDebug>
 
QtCompasSensor::QtCompasSensor(QWidget *parent)
: QGraphicsView(parent), Rect(0), text(0), CompasSensor(0)
{
QGraphicsScene *scene = new QGraphicsScene(this);
setScene(scene);
 
Rect = new QGraphicsRectItem();
 
text = new QGraphicsSimpleTextItem(Rect);
text->setBrush(Qt::gray);
scene->addItem(Rect);
 
CompasSensor = new QCompass(this);
inactiveTimer.setSingleShot(true);
 
if (!Timer.isActive())
Timer.start(20, this);
 
// start the sensor
if (!CompasSensor->isActive())
CompasSensor->start();
 
if (!CompasSensor->isActive())
{
qDebug() << "Compas Sensor didn't start!" << endl;
}
 
setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
}
 
bool QtCompasSensor::event(QEvent *event)
{
switch (event->type()) {
case QEvent::Timer:
if (static_cast<QTimerEvent*>(event)->timerId() == Timer.timerId())
updateCompasSensor(); // update the sensor data
break;
default:
break;
}
return QGraphicsView::event(event);
}
 
void QtCompasSensor::updateCompasSensor()
{
QCompassReading *reading = CompasSensor->reading();
qreal azi = 0.0f;
qreal calibrationLevel = 0.0f;
if (reading) {
azi = reading->azimuth();
calibrationLevel = reading->calibrationLevel();
 
// set the text and display it on the screen
QLocale c(QLocale::C);
text->setText("azimuth: " + c.toString(azi) + "\n\nCompass Sensor Calibration Level: " + c.toString(calibrationLevel));
 
}
}

Postconditions

Here is the QtCompassSensor Application's Screenshot. You can change the Compass Sensor data like azimuth and Calibration Level from Qt Simulator.

QtCompassSimulator.png QtCompassExample.png

Example Application

Example application can be found on the following link File:QtCompassSensorExample.zip.

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