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Geocoding

Geocoding is the process of transforming a street address or other description of a location into a (latitude, longitude) coordinate. Reverse geocoding is the process of transforming a (latitude, longitude) coordinate into a (partial) address. The amount of detail in a reverse geocoded location description may vary, for example one might contain the full street address of the closest building, while another might contain only a city name and postal code.

Geocoding is provided through the Location.service.geocoder variable which is an instance of the Geocoder interface.

Support​

Not every device will support geocoding. Android devices require a backend service that is not included in the core android framework, however most of the major handset providers do provide this.

In order to determine if geocoding is available you should check the isSupported flag.

if (Location.service.geocoder.isSupported)
{
    // Geocoding supported
}

If geocoding returns false you should not expect any of the other functionality of the Geocoder implementation to function.

Reverse Geocoding​

Reverse-geocoding requests take a latitude and longitude value and find a user-readable address.

This is done by using the getFromLocation() function and passing the latitude and longitude of interest.

This function will return either true or false indicating whether the operation was started successfully. You also need to pass in a maxResults value, indicating the maximum number of results you wish to be returned. 

var success:Boolean = Location.service.geocoder.getFromLocation( -27.493222, 152.9912969, 5 );

Calling getFromLocation() will result in an event being dispatch when the geocoding is complete:

  • GeocoderEvent.GET_FROM_LOCATION_COMPLETE: Dispatched when the call has completed and geocoding results are available

When the complete event is dispatched the event will contain the array of geocoded addresses. An address is represented by the Address class:

Location.service.geocoder.addEventListener( GeocoderEvent.GET_FROM_LOCATION_COMPLETE, completeHandler );
Location.service.geocoder.getFromLocation( -27.493222, 152.9912969, 5 );

function completeHandler( event:GeocoderEvent ):void 
{
    for each (var address:Address in event.addresses)
    {
        for (var i:int = 0; i < address.addressLines.length; i ++)
        {
            message( "ADDRESS: " + address.addressLines[i] );
        }
        message( "ADDRESS: locality : " + address.locality );
        message( "ADDRESS: postCode : " + address.postCode );
        message( "ADDRESS: country  : " + address.countryName );
    }
}

Forward Geocoding​

Forward-geocoding requests take a user-readable address and find the corresponding latitude and longitude value. Forward-geocoding requests may also return additional information about the specified location, such as a point of interest or building at that location.

This is done by using the getFromLocationName() function and passing the string description of the location.

This function will return either true or false indicating whether the operation was started successfully. You also need to pass in a maxResults value, indicating the maximum number of results you wish to be returned. 

var success:Boolean = Location.service.geocoder.getFromLocationName( "Parliament Dr, Canberra ACT 2600", 5 );

Calling getFromLocation() will result in an event being dispatch when the geocoding is complete:

  • GeocoderEvent.GET_FROM_LOCATION_NAME_COMPLETE: Dispatched when the call has completed and geocoding results are available

When the complete event is dispatched the event will contain the array of geocoded addresses. An address is represented by the Address class:

Location.service.geocoder.addEventListener( GeocoderEvent.GET_FROM_LOCATION_NAME_COMPLETE, completeHandler );
Location.service.geocoder.getFromLocationName( "Parliament Dr, Canberra ACT 2600", 5 );

function completeHandler( event:GeocoderEvent ):void 
{
    for each (var address:Address in event.addresses)
    {
        for (var i:int = 0; i < address.addressLines.length; i ++)
        {
            message( "ADDRESS: " + address.addressLines[i] );
        }
        message( "ADDRESS: locality : " + address.locality );
        message( "ADDRESS: postCode : " + address.postCode );
        message( "ADDRESS: country  : " + address.countryName );
    }
}