- Qt 5.5
- Qt Positioning
- Log File Position Source (C++)
- logfilepositionsource.cpp Example File
- Qt 5.5.1 Reference Documentation

# logfilepositionsource.cpp Example File

logfilepositionsource/logfilepositionsource.cpp

    /****************************************************************************
    **
    ** Copyright (C) 2015 The Qt Company Ltd.
    ** Contact: http://www.qt.io/licensing/
    **
    ** This file is part of the examples of the Qt Toolkit.
    **
    ** $QT_BEGIN_LICENSE:BSD$
    ** 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 The Qt Company Ltd 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."
    **
    ** $QT_END_LICENSE$
    **
    ****************************************************************************/
    #include <QtCore>

    #include "logfilepositionsource.h"

    LogFilePositionSource::LogFilePositionSource(QObject *parent)
        : QGeoPositionInfoSource(parent),
          logFile(new QFile(this)),
          timer(new QTimer(this))
    {
        connect(timer, SIGNAL(timeout()), this, SLOT(readNextPosition()));

        logFile->setFileName(":/simplelog.txt");
        if (!logFile->open(QIODevice::ReadOnly))
            qWarning() << "Error: cannot open source file" << logFile->fileName();
    }

    QGeoPositionInfo LogFilePositionSource::lastKnownPosition(bool /*fromSatellitePositioningMethodsOnly*/) const
    {
        return lastPosition;
    }

    LogFilePositionSource::PositioningMethods LogFilePositionSource::supportedPositioningMethods() const
    {
        return AllPositioningMethods;
    }

    int LogFilePositionSource::minimumUpdateInterval() const
    {
        return 500;
    }

    void LogFilePositionSource::startUpdates()
    {
        int interval = updateInterval();
        if (interval < minimumUpdateInterval())
            interval = minimumUpdateInterval();

        timer->start(interval);
    }

    void LogFilePositionSource::stopUpdates()
    {
        timer->stop();
    }

    void LogFilePositionSource::requestUpdate(int /*timeout*/)
    {
        // For simplicity, ignore timeout - assume that if data is not available
        // now, no data will be added to the file later
        if (logFile->canReadLine())
            readNextPosition();
        else
            emit updateTimeout();
    }

    void LogFilePositionSource::readNextPosition()
    {
        QByteArray line = logFile->readLine().trimmed();
        if (!line.isEmpty()) {
            QList<QByteArray> data = line.split(' ');
            double latitude;
            double longitude;
            bool hasLatitude = false;
            bool hasLongitude = false;
            QDateTime timestamp = QDateTime::fromString(QString(data.value(0)), Qt::ISODate);
            latitude = data.value(1).toDouble(&hasLatitude);
            longitude = data.value(2).toDouble(&hasLongitude);

            if (hasLatitude && hasLongitude && timestamp.isValid()) {
                QGeoCoordinate coordinate(latitude, longitude);
                QGeoPositionInfo info(coordinate, timestamp);
                if (info.isValid()) {
                    lastPosition = info;
                    emit positionUpdated(info);
                }
            }
        }
    }

    QGeoPositionInfoSource::Error LogFilePositionSource::error() const
    {
        return QGeoPositionInfoSource::NoError;
    }