请问用什么方法可使ListBox中的某一item不可用(disable)?(30分)

修改一下TLitbox,增加一个ItemEnabled属性或干脆从TListbox继承自己做一个。

"某一item不可用"是个什么效果? 不能选中?

给你做了一个:
unit SrwListBox;

interface

uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
StdCtrls;

type
TSrwListBox = class(TListBox)
private
FDisableItemS : string;
{ Private declarations }
procedure CNDrawItem(var Message: TWMDrawItem); message CN_DRAWITEM;
protected
{ Protected declarations }
public
procedure EnableItem(Index: Integer);
procedure DisableItem(Index: Integer);
function isDisable(Index: Integer):boolean;
procedure ClearDisableRec;
{ Public declarations }
published
{ Published declarations }
end;

procedure Register;

implementation

procedure TSrwListBox.disableItem(Index: Integer);
var disindex : string;
begin
disindex := ','+IntToStr(Index)+',';
if Pos(disindex,FDisableItems) = 0 then
FDisableItemS := FDisableItems + disindex;
// SendMessage(Handle, LB_SETITEMDATA, Index, 0);
SendMessage(Handle, LB_SETSEL, Longint(False),Index);
// Refresh;
end;

procedure TSrwListBox.EnableItem(Index: Integer);
var disindex : string;
begin
disindex := ','+IntToStr(Index)+',';
if Pos(disindex,FDisableItems) > 0 then
delete(FDisableItemS, Pos(disindex,FDisableItems), Length(disindex));
SendMessage(Handle, LB_SETSEL, Longint(False),Index);
// Refresh;
end;

function TSrwListBox.isDisable(Index: Integer):boolean;
var disindex : string;
begin
disindex := ','+IntToStr(Index)+',';
Result := Pos(disindex,FDisableItems) > 0;
end;

procedure TSrwListBox.ClearDisableRec;
begin
FDisableItems := '';
end;

procedure TSrwListBox.CNDrawItem(var Message: TWMDrawItem);
var
State: TOwnerDrawState;
idx : integer;
begin
with Message.DrawItemStruct^ do
begin
idx := Integer(itemID);
if Pos(','+IntToStr(idx)+',',FDisableItems) > 0 then
State := [odDisabled]
else
State := TOwnerDrawState(WordRec(LongRec(itemState).Lo).Lo);
Canvas.Handle := hDC;
Canvas.Font := Font;
Canvas.Brush := Brush;
if (Integer(itemID) >= 0) and (odSelected in State) then
begin
Canvas.Brush.Color := clHighlight;
Canvas.Font.Color := clHighlightText
end
else if (odDisabled in State) then
Canvas.Font.Color := clGray;
if Integer(itemID) >= 0 then
DrawItem(itemID, rcItem, State) else
Canvas.FillRect(rcItem);
if odFocused in State then DrawFocusRect(hDC, rcItem);
Canvas.Handle := 0;
end;
end;

procedure Register;
begin
RegisterComponents('Srw', [TSrwListBox]);
end;

end.

做得真够周到的，服务到家了。