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Provide position through QGeoPositionInfoSource



  • Dear all, I am making an application which must show the location of a ship. The actual location comes from outside the application which I am making. To show the location, I want to make use of the LocationDisplay class. So I started a default ArcGIS application in Qt Creator (I tried both a QML and C++ app), and made a class, which is derived from QGeoPositionInfoSource, according to this example, linked by LDanzinger-esristaff, also on this forum. However, I just can't seem to get it to work. It seems I just don't understand it, and to be hones I'm getting a bit frustrated :)

    My code is as follows:

    #ifndef SHIPPOSITIONSOURCE_H
    #define SHIPPOSITIONSOURCE_H
    
    #include <QGeoPositionInfoSource>
    
    class ShipPositionSource : public QGeoPositionInfoSource
    {
        Q_OBJECT
    
    public:
        explicit ShipPositionSource(QObject* parent = nullptr);
        ~ShipPositionSource();
    
        QGeoPositionInfo lastKnownPosition(bool fromSatellitePositioningMethodsOnly = false) const override;
        PositioningMethods supportedPositioningMethods() const override;
        int minimumUpdateInterval() const override;
        QGeoPositionInfoSource::Error error() const override;
    
    public slots:
        void startUpdates() override;
        void stopUpdates() override;
        void requestUpdate(int timeout = 0) override;
    
        QGeoPositionInfo currentPosition;
        QGeoPositionInfoSource::Error lastError = QGeoPositionInfoSource::NoError;
    
        bool started;
    };
    
    #endif // SHIPPOSITIONSOURCE_H
    
    

    That was the header, here the source:

    #include "shippositionsource.h"
    
    ShipPositionSource::ShipPositionSource(QObject* parent) :
        QGeoPositionInfoSource(parent)
    {
        setUpdateInterval(500);
        currentPosition.setCoordinate(QGeoCoordinate(52.920905, 4.862173));
        emit positionUpdated(currentPosition);
    }
    
    ShipPositionSource::~ShipPositionSource()
    {}
    
    void ShipPositionSource::startUpdates()
    {
        if(started)
            return;
    
        started = true;
        //TODO: start communication with bridge
    }
    
    void ShipPositionSource::stopUpdates()
    {
        if(!started)
            return;
    
        started = false;
    
        //TODO: stop communication with bridge
    }
    
    void ShipPositionSource::requestUpdate(int timeout)
    {
        Q_UNIMPLEMENTED();
    }
    
    QGeoPositionInfo ShipPositionSource::lastKnownPosition(bool fromSatellitePositioningMethodsOnly) const
    {
        Q_UNUSED(fromSatellitePositioningMethodsOnly);
        return currentPosition;
    }
    
    QGeoPositionInfoSource::PositioningMethods ShipPositionSource::supportedPositioningMethods() const
    {
        return QGeoPositionInfoSource::PositioningMethod::NoPositioningMethods;
    }
    
    int ShipPositionSource::minimumUpdateInterval() const
    {
        return updateInterval();
    }
    
    QGeoPositionInfoSource::Error ShipPositionSource::error() const
    {
        return lastError;
    }
    
    

    I made a Quick C++ app, called TestProject, and in TestProject.cpp I only edited the TestProject::setMapView method with the following lines:

    m_mapView = mapView;
    m_mapView->locationDisplay()->setPositionSource(&positionSource);
        m_mapView->locationDisplay()->setAutoPanMode(LocationDisplayAutoPanMode::Recenter);
    m_mapView->locationDisplay()->start();
    m_mapView->setMap(m_map);
    

    The result is that I don't see any location updated, or the map centering on the position I gave in the constructor. I must be doing something wrong or I don't understand something, but I don't see what. I would be very thankful for hints and tips!


  • Lifetime Qt Champion

    @JustAJ said in Provide position through QGeoPositionInfoSource:

    locationDisplay

    What type of Qt class is this? I think this is no Qt class but on from ESRI ArcGIS runtime SDK ( https://developers.arcgis.com/qt/latest/cpp/api-reference/esri-arcgisruntime-locationdisplay.html ) so you should better ask here as we don't have any experience with this library.
    Also - where did you define positionSource - are you sure it's alive after you leave the function (I would guess no)?



  • @Christian-Ehrlicher said in Provide position through QGeoPositionInfoSource:

    @JustAJ said in Provide position through QGeoPositionInfoSource:

    locationDisplay

    What type of Qt class is this? I think this is no Qt class but on from ESRI ArcGIS runtime SDK ( https://developers.arcgis.com/qt/latest/cpp/api-reference/esri-arcgisruntime-locationdisplay.html ) so you should better ask here as we don't have any experience with this library.
    Also - where did you define positionSource - are you sure it's alive after you leave the function (I would guess no)?

    I am terribly sorry, I mixed up some stuff. This is indeed from the ArcGIS SDK. I will go ask there.

    Yes, positionSource is alive at that position. I defined it as a private attribute of the TestProject class, in the header


  • Lifetime Qt Champion

    @JustAJ said in Provide position through QGeoPositionInfoSource:

    I defined it as a private attribute of the TestProject class, in the header

    I just asked because the other members seems to be prefixed with 'm_'. Also I would check QGeoPositionInfoSource::error() and other functions provided by QGeoPositionInfoSource to see if it is really valid.



  • @Christian-Ehrlicher said in Provide position through QGeoPositionInfoSource:

    @JustAJ said in Provide position through QGeoPositionInfoSource:

    I defined it as a private attribute of the TestProject class, in the header

    I just asked because the other members seems to be prefixed with 'm_'. Also I would check QGeoPositionInfoSource::error() and other functions provided by QGeoPositionInfoSource to see if it is really valid.

    I've worked quite some time in a .NET environment, so I'm not very fond of the prefixes. This code was from an example, which I modified to my preferences.
    Regarding the error() method, it is a pure virtual method, so besides my own implementation, no useful information can be gotten.


  • Lifetime Qt Champion

    @JustAJ said in Provide position through QGeoPositionInfoSource:

    so besides my own implementation

    What does this mean? You wrote an own QGeoPositionInfoSource? Did you actually check if it is working correctly?



  • @Christian-Ehrlicher said in Provide position through QGeoPositionInfoSource:

    @JustAJ said in Provide position through QGeoPositionInfoSource:

    so besides my own implementation

    What does this mean? You wrote an own QGeoPositionInfoSource? Did you actually check if it is working correctly?

    I don't think I understand what you mean... I made my own class which inherits from QGeoPositionInfoSource, as you can see in the code I provided. The QGeoPositionInfoSource::error() you mentioned is a pure virtual method, so I cannot use this method to troubleshout if something goes wrong in QGeoPositionInfoSource, that's what I mean.


  • Lifetime Qt Champion

    Ok, mixed it up :)