2011年08月13日星期六 10:49 A.M.

最终编辑 qhh_2008

在vc++中，对CListCtrl类有一个很常见的操作，即选中list中的若干项，然后单击左键进行拖拉，比较常见的是拖拉到CTreeCtrl的某个节点里，见资源管理器。在拖拉的操作过程中，鼠标处会画出选中项的图标，用于模拟显示，类似下图。

如果用户选中了多个项目，可以采用以下的算法来画图标：

const CImageList* CDragDrogDialog::CreateDragImageEx(CListCtrl *pList, LPPOINT lpPoint)
{
//如果没有选择任何行
if   (pList->GetSelectedCount() <= 0)
{
    return NULL;
}

CRect   rectSingle;
CRect   rectComplete(0,0,0,0);

//计算客户区图像的宽度
pList->GetClientRect(rectSingle);
int nWidth = rectSingle.Width();

//可视区的开始和结束行
int nTopIndex = pList->GetTopIndex() - 1;
int nBottomIndex = pList->GetTopIndex() + pList->GetCountPerPage() - 1;
//如果pList没有占满
if (nBottomIndex > (pList->GetItemCount() - 1))
{
   nBottomIndex = pList->GetItemCount() - 1;
}

//计算拖拉的图标尺寸,此时nTopIndex已经变为选择区的第一行
while (-1 != (nTopIndex = pList->GetNextItem(nTopIndex, LVNI_SELECTED)))
{
     if (nTopIndex > nBottomIndex)
     {
        break;
     }

     pList->GetItemRect(nTopIndex, rectSingle, LVIR_BOUNDS);

     if (rectSingle.left < 0)
     {
         rectSingle.left = 0;
     }

     if (rectSingle.right > nWidth)
     {
         rectSingle.right = nWidth;
     }

     rectComplete.UnionRect(rectComplete,   rectSingle);
}

CClientDC dcClient(this);
CDC    dcMem;
CBitmap   Bitmap;

if (!dcMem.CreateCompatibleDC(&dcClient))
{
    return NULL;
}

if (!Bitmap.CreateCompatibleBitmap(&dcClient, rectComplete.Width(), rectComplete.Height)))
{
     return NULL;
}

//填充拖拉的背景，一般选用绿色
CBitmap *pOldMemDCBitmap = dcMem.SelectObject(&Bitmap);
dcMem.FillSolidRect(0, 0, rectComplete.Width(), rectComplete.Height(), RGB(0, 255, 0));

//开始画图标
nTopIndex = pList->GetTopIndex() - 1;
while (-1 != (nTopIndex = pList->GetNextItem(nTopIndex, LVNI_SELECTED)))
{
  if (nTopIndex > nBottomIndex)
    {
        break;
   }

   CPoint pt;
   CImageList* pSingleImageList = pList->CreateDragImage(nIndex, &pt);

  if (pSingleImageList)
   {
       pList->GetItemRect(nTopIndex, rectSingle, LVIR_BOUNDS);
       pSingleImageList->Draw(&dcMem, 0, CPoint(rectSingle.left - rectComplete.left,     rectSingle.top - rectComplete.top),ILD_MASK);
       pSingleImageList->DeleteImageList();
      //一定要记得delete，否则溢出，见MSN
       delete pSingleImageList;
     }
}

dcMem.SelectObject(pOldMemDCBitmap);
CImageList* pCompleteImageList = new CImageList;
ASSERT(pCompleteImageList);
pCompleteImageList->Create(rectComplete.Width(), rectComplete.Height(), ILC_COLOR | ILC_MASK, 0, 1);
pCompleteImageList->Add(&Bitmap, RGB(0, 255, 0));
Bitmap.DeleteObject();

if (lpPoint)
{
   lpPoint->x = rectComplete.left;
   lpPoint->y = rectComplete.top;
}

return pCompleteImageList;

}

===========================================

http://group.gimoo.net/review/88101

【话题】CListCtrl如何实现拖动多个Items

2009-06-24 22:05:38　来自:superworld 浏览数：17次

我选中多项, 进行拖动的时候. 只有鼠标拖动的那一个item有效果.

如何构造拖动多个item拖动时候的cimagelist 实现类似资源管理器中拖动多项的效果

hyfang6673回复于24日22点18分　在BEGINDRAG是创建一个 CImageList,然后调用哪个BeginDrag就可以了,然后在拖动完毕是自己处理一下就可以了
CImageList* CAptFileZillaDlg::CreateDragImageEx(CListCtrl *pList, LPPOINT lpPoint)
{
if (pList->GetSelectedCount() <= 0)
return NULL; // no row selected

DWORD dwStyle = GetWindowLong(pList->m_hWnd, GWL_STYLE) & LVS_TYPEMASK;

CRect rectComplete(0, 0, 0, 0);

// Determine List Control Client width size
CRect rectClient;
pList->GetClientRect(rectClient);
int nWidth = rectClient.Width() + 50;

// Start and Stop index in view area
int nIndex = pList->GetTopIndex() - 1;
int nBottomIndex = pList->GetTopIndex() + pList->GetCountPerPage();
if (nBottomIndex > (pList->GetItemCount() - 1))
nBottomIndex = pList->GetItemCount() - 1;

// Determine the size of the drag image (limited for rows visibled and client width)
while ((nIndex = pList->GetNextItem(nIndex, LVNI_SELECTED)) != -1)
{
if (nIndex > nBottomIndex)
break;

CRect rectItem;
pList->GetItemRect(nIndex, rectItem, LVIR_BOUNDS);

if (rectItem.left < 0)
rectItem.left = 0;

if (rectItem.right > nWidth)
rectItem.right = nWidth;

rectComplete.UnionRect(rectComplete, rectItem);
}

// Create memory device context
CClientDC dcClient(this);
CDC dcMem;
CBitmap Bitmap;

if (!dcMem.CreateCompatibleDC(&dcClient))
return NULL;

if (!Bitmap.CreateCompatibleBitmap(&dcClient, rectComplete.Width(), rectComplete.Height()))
return NULL;

CBitmap *pOldMemDCBitmap = dcMem.SelectObject(&Bitmap);
// Use green as mask color
dcMem.FillSolidRect(0, 0, rectComplete.Width(), rectComplete.Height(), RGB(0,255,0));

// Don't use antialiased font for the dragimages
CFont *pFont = pList->GetFont();
LOGFONT lf;
pFont->GetLogFont(&lf);
lf.lfQuality = NONANTIALIASED_QUALITY;
CFont newFont;
newFont.CreateFontIndirect(&lf);

CFont *oldFont = dcMem.SelectObject(&newFont);

// Paint each DragImage in the DC
nIndex = pList->GetTopIndex() - 1;
while ((nIndex = pList->GetNextItem(nIndex, LVNI_SELECTED)) != -1)
{
if (nIndex > nBottomIndex)
break;

TCHAR buffer[1000];
LVITEM item = {0};
item.mask = LVIF_TEXT | LVIF_IMAGE;
item.iItem = nIndex;
item.pszText = buffer;
item.cchTextMax = 999;

pList->GetItem(&item);

// Draw the icon
CImageList* pSingleImageList = pList->GetImageList((dwStyle == LVS_ICON)?LVSIL_NORMAL:LVSIL_SMALL);
if (pSingleImageList)
{
CRect rectIcon;
pList->GetItemRect(nIndex, rectIcon, LVIR_ICON);

IMAGEINFO info;
pSingleImageList->GetImageInfo(item.iImage, &info);
CPoint p((rectIcon.left - rectComplete.left + rectIcon.right - rectComplete.left) / 2 - (info.rcImage.right - info.rcImage.left) / 2,
(rectIcon.top - rectComplete.top + rectIcon.bottom - rectComplete.top) / 2 - (info.rcImage.bottom - info.rcImage.top) / 2 + ((dwStyle == LVS_ICON)?2:0));

pSingleImageList->Draw( &dcMem, item.iImage,
p,
ILD_TRANSPARENT);
}

// Draw the text
CString text;
text = item.pszText;
CRect textRect;
pList->GetItemRect( nIndex, textRect, LVIR_LABEL );
textRect.top -= rectComplete.top - 2;
textRect.bottom -= rectComplete.top + 1;
textRect.left -= rectComplete.left - 2;
textRect.right -= rectComplete.left;

DWORD flags = DT_END_ELLIPSIS | DT_MODIFYSTRING;
if (dwStyle == LVS_ICON)
flags |= DT_CENTER | DT_WORDBREAK;
dcMem.DrawText(text, -1, textRect, flags);
}

dcMem.SelectObject(oldFont);

dcMem.SelectObject(pOldMemDCBitmap);

// Create drag image(list)
CImageList* pCompleteImageList = new CImageList;
pCompleteImageList->Create(rectComplete.Width(), rectComplete.Height(), ILC_COLOR32 | ILC_MASK, 0, 1);
pCompleteImageList->Add(&Bitmap, RGB(0, 255, 0)); // Green is used as mask color
Bitmap.DeleteObject();

if (lpPoint)
{
lpPoint->x = rectComplete.left;
lpPoint->y = rectComplete.top;
}

return pCompleteImageList;
}

chenhua回复于24日22点30分　

就是这个效果，，，

南方-1996回复于24日22点44分　

IDropSource
IDropTarget

要继承这两个类来协助完成，详细的情况那么需要找相关的例子来完成。

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