HI,ALL;
This article below is from forum nokia wiki.

This document will very briefly explain how to change the active theme on a S60 3rd Edition device.

The information in this document is provided as is and the code samples are not meant to be of commercial quality.

Please note that you need to download and install the Extensions plug-in package for S60 3rd Edition SDK for Symbian OS, for C++, MR, Version 3 from here to gain access to the needed APIs.

At the time of writing, the API plugin is only available for S60 3rd MR.

1. CONNECT TO SKIN SERVER

#include // aknskinsrv.lib

RAknsSrvSession skinsSession;
User::LeaveIfError( skinsSession.Connect( this ) );
CleanupClosePushL( skinsSession );
2. FETCH THE PACKAGE ID OF THE CURRENT SKIN

#include // centralrepository.lib
#include
…// iOriginalSkinPid is of type TAknsPkgID
void CMyThemeManager::StoreCurrentSkinIdL()
{
TAknsPkgIDBuf pidBuf;
CRepository* repository =
CRepository::NewL( KCRUidPersonalisation );
TInt retVal = repository->Get( KPslnActiveSkinUid, pidBuf );
delete repository;
repository = NULL;
iOriginalSkinPid.SetFromDesL( pidBuf );
}3. GET A LIST OF INSTALLED SKIN PACKAGES

Please see aknssrvclient.h file for more details on how to work with skins residing on memory card.

CArrayPtr< CAknsSrvSkinInformationPkg >* skinInfoArray =
skinsSession.EnumerateSkinPackagesL();
CleanupStack::PushL( skinInfoArray );4. GO THROUGH INSTALLED PACKAGES AND SWITCH TO THE FIRST AVAILABLE NEW SKIN

TInt retValue( KErrNone );
TInt i( 0 );
if ( skinInfoArray->Count() > 0 )
{
for ( i; i < skinInfoArray->Count(); i++ )
{
TAknsPkgID pkgId = skinInfoArray->At( i )->PID();
if ( pkgId != iOriginalSkinPid )
{
//Activate a complete skin package at once.
retValue = skinsSession.SetAllDefinitionSets( pkgId );
if ( retValue == KErrNone )
{
SetNewSkinIdL( pkgId );
}
break;
}
}
}5. SAVE THE NEW SKIN PACKAGE ID IN CENTRAL REPOSITORY

void CMyThemeManager::SetNewSkinIdL( TAknsPkgID aPkgId )
{
TAknsPkgIDBuf pidBuf;
aPkgId.CopyToDes( pidBuf );
CRepository* repository =
CRepository::NewL( KCRUidPersonalisation );
TInt retVal = repository->Set( KPslnActiveSkinUid, pidBuf );

// KPslnActiveSkinLocation has to be changed also
// if new skin resides on mmc whereas old one resided in phone mem
// ...and vice versa

delete repository;
repository = NULL;
}6. FREE ALLOCATED RESOURCES (FROM PARTS 1&3)

skinInfoArray->ResetAndDestroy();
CleanupStack::PopAndDestroy( 2 ); // skinsSession, skinInfoArray
7.NECESSARY ABABILITIES
Writte devicedata.
the article ended.

I use the code in my program to change the active theme .Luckily,It could change the system
theme,but when I exit my program ,a kern exec 3 happen. I thought two days,but I still find
out the solution to it.I think this line "retValue = skinsSession.SetAllDefinitionSets( pkgId );"
cause the error.when I delete this line the error don't happen.But I can't delete this line ,
because this line set the new theme.
who can tell me the solution?
think you in advanced!!!