Retrieving location information

These classes demonstrates how to obtain information related to the current location of the mobile device.

Article Metadata

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Article

Created: Den123 (21 Apr 2008)

Last edited: hamishwillee (07 Feb 2012)

Headers required:

#include <lbs.h>
#include <lbspositioninfo.h>
#include <lbssatellite.h>

Link against:

LIBRARY  lbs.lib

Classes:

// helper class-observer
class MPositionReaderObserver
{
   public:
      // if successful reading
      virtual void ReadingComplete( TPositionInfoBase& aPosInfo ) = 0;
      // if error occurred
      virtual void ReadingError( TInt aErrorNo ) = 0;
};
 
// location info reader
class CPositionReader : public CActive
{
   public:	
      static CPositionReader* NewL( MPositionReaderObserver* anObserver );
      ~CPositionReader();
 
      // requests for reading
      void ReadPosInfo();
      void ReadCourseInfo();
      void ReadSatelliteInfo();
 
      // data access
      const TPositionInfo& PosInfo();
      const TPositionCourseInfo& CourseInfo();
      const TPositionSatelliteInfo& SatelliteInfo();
 
   public: // from CActive	          
      void RunL();
      void DoCancel();
 
   private:
      CPositionReader();
      void ConstructL( MPositionReaderObserver* anObserver );	  
      void ReadInternal( TPositionInfoBase& anInfo );
 
   private:	   	   
      MPositionReaderObserver* iObserver;
 
      // used to make the primary connection to the location server	   
      RPositionServer iServer;
      // used to create a sub-session with the server 
      RPositioner iPositioner;
 
      TPositionInfoBase*     iCurInfo;  // points to the current info
      TPositionInfo          iPositionInfo;          // location info
      TPositionCourseInfo    iPositionCourseInfo;    // course info
      TPositionSatelliteInfo iPositionSatelliteInfo; // satellites info
};

The body:

// factory
CPositionReader* CPositionReader :: NewL( MPositionReaderObserver* anObserver )
{
   CPositionReader* self = new (ELeave) CPositionReader();
   CleanupStack :: PushL( self );
   self->ConstructL( anObserver );
   CleanupStack :: Pop( self );	
   return self;
}
 
// c++ destructor
CPositionReader :: ~CPositionReader()
{
   Cancel();
   iPositioner.Close();
   iServer.Close();	
}
 
void CPositionReader :: ReadPosInfo()
{
   ReadInternal( iPositionInfo );
}
const TPositionInfo& CPositionReader :: PosInfo()
{
   return iPositionInfo;
}
 
void CPositionReader :: ReadCourseInfo()
{
   ReadInternal( iPositionCourseInfo );
}
const TPositionCourseInfo& CPositionReader :: CourseInfo()
{
   return iPositionCourseInfo;
}
 
void CPositionReader :: ReadSatelliteInfo()
{
   ReadInternal( iPositionSatelliteInfo );
}
const TPositionSatelliteInfo& CPositionReader :: SatelliteInfo()
{
   return iPositionSatelliteInfo;
}
 
void CPositionReader :: RunL()
{
   if( iStatus == KErrNone )
   {
      // location retrieved. Operation finished.
      iObserver->ReadingComplete( *iCurInfo );
   }
   else
      // error occurred 
      iObserver->ReadingError( iStatus.Int() );
}
 
void CPositionReader :: DoCancel()
{	
   // cancel update notify
   iPositioner.CancelRequest( EPositionerNotifyPositionUpdate );	
}
 
CPositionReader :: CPositionReader():
	CActive( CActive :: EPriorityStandard )
{
   CActiveScheduler :: Add( this );
}
 
void CPositionReader :: ConstructL( MPositionReaderObserver* anObserver )
{
   iObserver = anObserver;
 
    // connect to the location server
   User :: LeaveIfError( iServer.Connect() );
 
    // open the default positioner
   User :: LeaveIfError( iPositioner.Open( iServer ) );
 
   _LIT( KAppName, "YourAppName" ); // define your application name
   User::LeaveIfError( iPositioner.SetRequestor(
                          CRequestor :: ERequestorService,
                          CRequestor :: EFormatApplication,
                          KAppName ) );
 
   // set maximum allowed time for a location request
   const TInt KTimeout = 50000000; // 50 sec
   TTimeIntervalMicroSeconds timeOut( KTimeout );
   TPositionUpdateOptions updateOptions;
   updateOptions.SetUpdateTimeOut( timeOut );
   User::LeaveIfError( iPositioner.SetUpdateOptions( updateOptions ) );    
}
 
 
void CPositionReader :: ReadInternal( TPositionInfoBase& anInfo )
{
   iCurInfo = &anInfo;
 
   // prepare active object 
   Cancel();
   iStatus = KRequestPending;	
 
   // issuer request
   iPositioner.NotifyPositionUpdate( anInfo, iStatus );
   SetActive();
}

How to use:

• implement interface MPositionReaderObserver in your class
• include CPositionReader* iReader as a class member
• activate request:

iReader = CPositionReader :: NewL( this ); // new reader
iReader->ReadSatelliteInfo();   // request satellites info

• process results of reading:

void YourClass :: ReadingComplete( TPositionInfoBase& aPosInfo )
{
   TPositionSatelliteInfo& info = ( TPositionSatelliteInfo& )aPosInfo;
   TInt iSatellitesInView = info.NumSatellitesInView(); // count of satellites in view 
        iSatellitesUsed   = info.NumSatellitesUsed();   // count of used satellites
   ...
}

Related Links:

• Landmarks/web client example using Carbide.c++ and UI designer
• How to use Landmarks API
• How to select and show a landmark
• How to compact local landmark databases
• How to export landmarks from database to file
• How to import landmarks from file to database
• Execution of landmark operations
• How to obtain and save current location
• How to manage landmark categories