Qt 5.8 | Qt Positioning | Log File Position Source (C++) | logfilepositionsource.cpp Example File

Qt 5.8.0 Reference Documentation

# logfilepositionsource.cpp Example File

logfilepositionsource/logfilepositionsource.cpp

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      ** This file is part of the examples of the Qt Toolkit.
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      #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;
      }