illegal use of non-static member

hi!
i am a totally newbie either with c++ and symbian programming, and i'm trying to develop a simple and minimal image viewer just to make a little practice.
i attached the program in the case my explanation will not be of much use.
i still have to develop the slideshow feature but i will do this later. now i have problem in listing bitmaps names to browse and select for viewing.
i used some of the engine code from the Graphics Tutorial on symbian.com in my AppUi.. but i've got problems (and also that's for displaying thumbnails, not file names but i'll change this later).. the compiler gives me a "illegal use of a non-static member" error. this error is about a ConstructL which i call in my AppUi.

Here's the code:

this is taken from the graphics tutorial

CListFiles* CListFiles::NewL()
{
CListFiles* self = new (ELeave) CListFiles();
CleanupStack::PushL(self);
self->ConstructL();
CleanupStack::Pop();
return self;
}

void CListFiles::ConstructL()
{
iLoadUtility = CMdaImageFileToBitmapUtility::NewL(*this);
iImageNames = new(ELeave) CArrayVarFlat<HBufC*>(1);
iBitmaps = new(ELeave) CArrayVarFlat<CFbsBitmap*>(1);
CollectFilesL();
}

and here's the error

void CProvaAppUi::ConstructL()
{
CQikAppUi::ConstructL();
CListFiles::ConstructL(); //here's the error
...

i would really pleased if you'd like to help me.. i really need to get a little skilled in order to make a future (hope i'll end it before july) simple project for my degree.
cheers,
TOOL