Moving items in a ListView

This is a discussion on Moving items in a ListView within the Windows Programming forums, part of the Platform Specific Boards category; Since it seems the ListView control had no real way to move items, I attempted to write my own. It's ...

  1. #1
    int x = *((int *) NULL); Cactus_Hugger's Avatar
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    Moving items in a ListView

    Since it seems the ListView control had no real way to move items, I attempted to write my own. It's not working. It moves the item, but the subitems of the new item are all blank.

    Here's the code...
    Code:
    /*
     * Moves the selected list view item up or down.
     * hwnd = list view
     * change = -1 for up 1, 1 for down 1, -2 for up two, etc.
     * Returns 0 on success, nonzero on failure.
     */
    int ListView_Move(HWND hwnd, int change)
    {
    	LV_ITEM lvi = {0};
    	int iOld, iNew = -1;
    	char text_buf[1024];
    	int iColumn, nColumns, ret;
    
    	if(!change) return 1;
    	if(change > 0) ++change;
    
    	iOld = ListView_GetNextItem(hwnd, -1, LVNI_SELECTED);
    	if(iOld == -1) return 1;
    
    	lvi.mask = LVIF_TEXT | LVIF_IMAGE | LVIF_STATE | LVIF_PARAM;
    	lvi.iItem = iOld;
    	lvi.pszText = text_buf;
    	lvi.cchTextMax = 1024;
    
    	// Create the new item, with all the info of the old...
    	ListView_GetItem(hwnd, &lvi);
    
    	lvi.iItem += change;
    	iNew = ListView_InsertItem(hwnd, &lvi);
    	// If we create an item above the old one, then the old one moves down one...
    	if(change < 0) ++iOld;
    
    	nColumns = Header_GetItemCount(ListView_GetHeader(hwnd));
    
    	sprintf(text_buf, "%d columns...", nColumns);
    	MessageBox(GetParent(hwnd), text_buf, "", 0);
    
    	// Copy all the subitems from the old to the new
    	for(iColumn = 1; iColumn < nColumns; ++iColumn)
    	{
    		ZeroMemory(&lvi, sizeof(LV_ITEM));
    
    		lvi.mask = LVIF_TEXT | LVIF_IMAGE | LVIF_STATE | LVIF_PARAM;
    		lvi.iItem = iOld;
    		lvi.iSubItem = iColumn;
    		lvi.pszText = text_buf;
    		lvi.cchTextMax = 1024;
    		ListView_GetItem(hwnd, &lvi);
    		MessageBox(GetParent(hwnd), text_buf, "", 0);
    
    		lvi.iItem = iNew;
    		ret = ListView_SetItem(hwnd, &lvi);
    		sprintf(text_buf, "%d = ret... (iNew = %d) last_err = %d?", ret, iNew, GetLastError());
    		MessageBox(hwnd, text_buf, "", 0);
    	}
    
    	ListView_DeleteItem(hwnd, iOld);
    
    	return 0;
    }
    The message boxes are for debugging...
    The first one says there are 3 columns (correct), the second one should say what each subitem's text is (it does, so: correct), and the last tells other stuff. (The return value of ListView_SetItem, iNew (the index of the new item), and GetLastError().) The last messagebox says 0, a correct index value, and 0. GetLastError() is returning 0 (success) and ListView_SetItem is returning 0 (failure). (It apperantly doesn't call SetLastError...)

    Why, though, does ListView_SetItem fail? I'm only changing the iItem member... the rest of it was filled in by ListView_GetItem().

    Thanks in Advance for any help...
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  2. #2
    Yes, my avatar is stolen anonytmouse's Avatar
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    According to MSDN, sub-items do not support LVIF_STATE or LVIF_PARAM:
    Quote Originally Posted by MSDN ListView_SetItem
    You cannot set the state or lParam members for subitems because subitems do not have these attributes. In version 4.70 and later, you can set the iImage member for subitems.
    Therefore, the solution is simple, just remove these mask values when you get and set the sub-items:
    Code:
    lvi.mask = LVIF_TEXT | LVIF_IMAGE;
    You may also wish to add a call to move the focus and selection before deleting the old item:
    Code:
    	ListView_SetItemState(hwnd, iNew, LVIS_SELECTED | LVIS_FOCUSED, LVIS_SELECTED | LVIS_FOCUSED);
    	ListView_DeleteItem(hwnd, iOld);
    I thought of a novel way to do this, although much less efficient than your code:
    Code:
    /*
     * ListView_Move helper function.
     */
    int CALLBACK LVMoveCompareFunc(LPARAM lParam1, LPARAM lParam2, LPARAM lParamSort)
    {
    	struct CTX { int src, trg; } *pctx = (struct CTX*) lParamSort;
    
    	if (lParam1 == pctx->src)
    		return (lParam2 >= pctx->trg ? -1 : +1);
    	else if (lParam2 == pctx->src)
    		return (lParam1 >= pctx->trg ? +1 : -1);
    	else
    		return (lParam1 >= lParam2   ? +1 : -1);
    }
    
    /*
     * Moves the selected list view item up or down.
     * hwnd = list view
     * change = -1 for up 1, 1 for down 1, -2 for up two, etc.
     * Returns TRUE on success, FALSE on failure.
     */
    BOOL ListView_Move(HWND hwnd, int change)
    {
    	struct CTX { int src, trg; } ctx;
    
    	ctx.src = ListView_GetNextItem(hwnd, -1, LVNI_SELECTED);
    	ctx.trg = ctx.src + change + (change > 0 ? 1 : 0);
    
    	return ListView_SortItemsEx(hwnd, LVMoveCompareFunc, (LPARAM) &ctx);
    }

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