Revision as of 16:43, 4 June 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 is not so fast to access to 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.start();
        }
    }
 
    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.