dcsimg

Sort list (numeric/text) using callback

WEBINAR:
On-Demand

Desktop-as-a-Service Designed for Any Cloud ? Nutanix Frame


This is a small class which permits to sort list controls. It works "substituting" every original item data with a small class (preserving the value), sort it using the standard (fast!) list control way, and then putting the things right back.

Step 1: implementing the class

The class will contain two subclasses to manage numeric and text column data. The numeric is provided to avoid the sorting of 11 before 2 as it would occur with string comparison; there are also 4 comparing routines (for ascending and descending text and integer columns).

The header file of the class should be like this:

class CSortClass
{
public:
	CSortClass(CListCtrl * _pWnd, const int _iCol, const bool _bIsNumeric);
	virtual ~CSortClass();
	
	int iCol;
	CListCtrl * pWnd;
	bool bIsNumeric;
	void Sort(const bool bAsc);
	
	static int CALLBACK CompareAsc(LPARAM lParam1, LPARAM lParam2, LPARAM lParamSort);
	static int CALLBACK CompareDes(LPARAM lParam1, LPARAM lParam2, LPARAM lParamSort);
	
	static int CALLBACK CompareAscI(LPARAM lParam1, LPARAM lParam2, LPARAM lParamSort);
	static int CALLBACK CompareDesI(LPARAM lParam1, LPARAM lParam2, LPARAM lParamSort);
	
public:
	class CSortItem
	{
	public:
		virtual  ~CSortItem();
		CSortItem(const DWORD _dw, const CString &_txt);
		CString txt;
		DWORD dw;
	};
	class CSortItemInt
	{
	public:
		CSortItemInt(const DWORD _dw, const CString &_txt);
		int iInt ;
		DWORD dw;
	};
};

The CPP file will implement all the above:

/////////////////////////////////////////////////////////////////////////////
// CSortClass

CSortClass::CSortClass(CListCtrl * _pWnd, const int _iCol, const bool _bIsNumeric)
{
	iCol = _iCol;
	pWnd = _pWnd;
	bIsNumeric = _bIsNumeric;
	
	ASSERT(pWnd);
	int max = pWnd->GetItemCount();
	DWORD dw;
	CString txt;
	if (bIsNumeric)
	{
		for (int t = 0; t < max; t++)
		{
			dw = pWnd->GetItemData(t);
			txt = pWnd->GetItemText(t, iCol);
			pWnd->SetItemData(t, (DWORD) new CSortItemInt(dw, txt));
		}
	}
	else
	{
		for (int t = 0; t < max; t++)
		{
			dw = pWnd->GetItemData(t);
			txt = pWnd->GetItemText(t, iCol);
			pWnd->SetItemData(t, (DWORD) new CSortItem(dw, txt));
		}
	}
}

CSortClass::~CSortClass()
{
	ASSERT(pWnd);
	int max = pWnd->GetItemCount();
	if (bIsNumeric)
	{
		CSortItemInt * pItem;
		for (int t = 0; t < max; t++)
		{
			pItem = (CSortItemInt *) pWnd->GetItemData(t);
			ASSERT(pItem);
			pWnd->SetItemData(t, pItem->dw);
			delete pItem;
		}
	}
	else
	{
		CSortItem * pItem;
		for (int t = 0; t < max; t++)
		{
			pItem = (CSortItem *) pWnd->GetItemData(t);
			ASSERT(pItem);
			pWnd->SetItemData(t, pItem->dw);
			delete pItem;
		}
	}
}

void
CSortClass::Sort(const bool bAsc)
{
	if (bIsNumeric)
	{
		if (bAsc)
			pWnd->SortItems(CompareAscI, 0L);
		else
			pWnd->SortItems(CompareDesI, 0L);
	}
	else
	{
		if (bAsc)
			pWnd->SortItems(CompareAsc, 0L);
		else
			pWnd->SortItems(CompareDes, 0L);
	}
}

int CALLBACK CSortClass::CompareAsc(LPARAM lParam1, LPARAM lParam2, LPARAM lParamSort)
{
	CSortItem * i1 = (CSortItem *) lParam1;
	CSortItem * i2 = (CSortItem *) lParam2;
	ASSERT(i1 && i2);
	return i1->txt.CompareNoCase(i2->txt);
}

int CALLBACK CSortClass::CompareDes(LPARAM lParam1, LPARAM lParam2, LPARAM lParamSort)
{
	CSortItem * i1 = (CSortItem *) lParam1;
	CSortItem * i2 = (CSortItem *) lParam2;
	ASSERT(i1 && i2);
	return i2->txt.CompareNoCase(i1->txt);
}

int CALLBACK CSortClass::CompareAscI(LPARAM lParam1, LPARAM lParam2, LPARAM lParamSort)
{
	CSortItemInt * i1 = (CSortItemInt *) lParam1;
	CSortItemInt * i2 = (CSortItemInt *) lParam2;
	ASSERT(i1 && i2);
	if (i1->iInt == i2->iInt) return 0;
	return i1->iInt > i2->iInt ? 1 : -1;
}

int CALLBACK CSortClass::CompareDesI(LPARAM lParam1, LPARAM lParam2, LPARAM lParamSort)
{
	CSortItemInt * i1 = (CSortItemInt *) lParam1;
	CSortItemInt * i2 = (CSortItemInt *) lParam2;
	ASSERT(i1 && i2);
	if (i1->iInt == i2->iInt) return 0;
	return i1->iInt < i2->iInt ? 1 : -1;
}

CSortClass::CSortItem::CSortItem(const DWORD _dw, const CString & _txt)
{
	dw = _dw;
	txt = _txt;
}

CSortClass::CSortItem::~CSortItem()
{
}

CSortClass::CSortItemInt::CSortItemInt(const DWORD _dw, const CString & _txt)
{
	iInt = atoi(_txt);
	dw = _dw;
}

Step 2: using it

The class is designed to be easy usable. In answer to a column click message in a list control, we can write something like this:
void CMyListCtrl::OnColumnclick(NMHDR* pNMHDR, LRESULT* pResult) 
{
	NM_LISTVIEW* pNMListView = (NM_LISTVIEW*)pNMHDR;
	
	// bAscending will be use to order from lower to higher or higher to lower
	bool bAscending = true;
	
	CSortClass csc(this, pNMListView->iSubItem, bAscending);
	csc.Sort(bAsc);
	
	*pResult = 0;
}



This article was originally published on August 6th, 1998

Most Popular Programming Stories

More for Developers

RSS Feeds

Thanks for your registration, follow us on our social networks to keep up-to-date