Categories: Symbian C++ | Location Based Services | How To | Code Examples

This page was last modified 06:06, 23 April 2008.

From Forum Nokia Wiki

The following code snippet demonstrates how to use class CPositionReader for obtaining current device position. This snippet also demonstrates, how to find the nearest landmark according to the current position.

Your class should implement interface CPositionReaderObserver and include instance of CPositionReader as a memeber.

It is necessary to include the following additional headers:

• epos_landmarks.h
• epos_cposlmitemiterator.h
• epos_cposlandmarkdatabase.h

Start async. request:

iReader = CPositionReader :: NewL( this );	
iReader->ReadPosInfo();

You should add the following code in the method ReadingComplete() for reading current location and finding the nearest landmark:

// read result device position
TPositionInfo& info = ( TPositionInfo& )aPosInfo;
TPosition position;
info.GetPosition( position );
   
// open default landmark DB
CPosLandmarkDatabase* db = CPosLandmarkDatabase :: OpenL();
CleanupStack :: PushL( db );
   
// create iterator
CPosLmItemIterator* iter = db->LandmarkIteratorL();        
CleanupStack :: PushL( iter );
 
// distance between device position and current landmark
TReal32 distance = KMaxTReal32;
   
TPosLmItemId itemId = iter->NextL(),  // current landmark ID
             resultItemId = KPosLmNullItemId; // nearest landmark ID
while( itemId != KPosLmNullItemId )	   
{
   // read current landmark
   CPosLandmark* lm = db->ReadLandmarkLC( itemId );
	   
   // get current landmark position
   TPosition lmPosition;
   if( lm->GetPosition( lmPosition ) == KErrNone  )
   {
      TReal32 d;
      // check distance
      if( position.Distance( lmPosition, d ) == KErrNone && d < distance )
      {	   
         resultItemId = itemId;
         distance = d;
      }		   		  		   
   }	   	   
 
   // read next landmark ID
   itemId = iter->NextL();	   
   CleanupStack :: PopAndDestroy(); // lm
}
 
// landmark was found
if( resultItemId != KPosLmNullItemId )
{
   // read landmark from DB
   CPosLandmark* resultLm = db->ReadLandmarkLC( resultItemId );
	   
   // read landmark name
   TPtrC lmName;
   resultLm->GetLandmarkName( lmName );
	   
   // show nearest landmark name
   CAknInformationNote* informationNote;
   informationNote = new ( ELeave ) CAknInformationNote;
   informationNote->ExecuteLD( lmName );			
 
   CleanupStack :: PopAndDestroy(); // resultLm
}
   
CleanupStack :: PopAndDestroy( 2 ); // iter db