Revision as of 04:17, 11 October 2012

Introduction

Reverse geocoding is the process of back (reverse) coding of a point location (latitude, longitude) to a readable address or place name. This permits the identification of nearby street addresses, places, and/or areal subdivisions such as neighbourhoods, county, state, or country. Combined with geocoding and routing services, reverse geocoding is a critical component of mobile location-based services.
Nokia provides one of the best location based services available and reverse geocoding is well supported in Qt/C++ and HTML5, but sometimes could be tricky to access this service from QML.
QReverseGeocode provide a quick and easy solution to manage reverse geocoding from QML.

Installation

1. Download source code from here
2. Include QReverseGeocode directory into your project

.pro

include(./qreversegeocode/reversegeocode.pri)

main.cpp

#include <QtGui/QApplication>
#include "qmlapplicationviewer.h"
 
#include <QtDeclarative>
#include "qreversegeocode.h"
 
Q_DECL_EXPORT int main(int argc, char *argv[])
{
    QScopedPointer<QApplication> app(createApplication(argc, argv));
 
    qmlRegisterType<QReverseGeocode>("QReverseGeocode", 1, 0, "QReverseGeocode");
 
    QmlApplicationViewer viewer;
    viewer.setMainQmlFile(QLatin1String("qml/QReverseGeocodeSample/main.qml"));
    viewer.showExpanded();
 
    return app->exec();
}

QML

Note: QReverseGeocode have to be used in conjunction with PositionSource component as shown below

import QtQuick 1.1
import com.nokia.symbian 1.1
import QtWebKit 1.0
import QtMobility.location 1.2
import QReverseGeocode 1.0
 
Page {
    id: mainPage
 
    Text {
          id: place
          text: ""
     }
 
    PositionSource {
        id: positionSource
        active: true
 
        onPositionChanged: {
            reverseGeocoder.latitude  = positionSource.position.coordinate.latitude
            reverseGeocoder.longitude = positionSource.position.coordinate.longitude
            reverseGeocoder.process();
        }
    }
 
    QReverseGeocode {
        id:reverseGeocoder
        onReverseGeocodeFinished:{
            place.text=reverseGeocoder.postCode+" "+reverseGeocoder.city
        }
    }
 
}

API Reference

Properties ( To use before calling process() )

• latitude - Property that hold the latitude value
• longitude - Property that hold the longitude value

Properties ( Filled when onReverseGeocodeFinished() is emitted )

• city - Property that hold the city value
• postCode - Property that hold post code value
• street - Property that hold the street value
• country - Property that hold the country value

Signals (handlers)

• onLatitudeChanged() - Invoked when latitude property changes.
• onLongitudeChanged() - Invoked when the longitude changes.
• onReverseGeocodeFinished() - Invoked when the reverse geocode process is finished.

Slots

• process() - Start the reverse geocoding process. Before calling this method the latitude and longitude properties have to be filled.

onReverseGeocodeFinished

When onReverseGeocodeFinished() is emitted all address informations are stored into the properties described before, so you can compose your informations in the way you need. For example you could need to display just post code and city:

onReverseGeocodeFinished:{
            place.text=reverseGeocoder.postCode+" "+reverseGeocoder.city
}

or just city and country:

onReverseGeocodeFinished:{
            place.text=reverseGeocoder.city+" "+reverseGeocoder.country
}

rather than all informations:

onReverseGeocodeFinished:{
            place.text=reverseGeocoder.street+"<br/>"+reverseGeocoder.postCode+" "+reverseGeocoder.city+"<br/>"+reverseGeocoder.country
}