关于TListView的OnChanging消息(100分)

在TListView的OnChanging消息中如何区分以下操作：
1、无选择项目时，点击一项目选中；
2、有选择项目时，点击另一项目改变选择；
3、有选择项目时，点击原选择项目；
4、点击项目前的CheckBox，改变CheckBox的选择状态（包括当前选择的项目、其它项目）；

1、2：
if ListView1.Selected = nil then
ShowMessage('无选择项目时，点击一项目选中')
else
ShowMessage('有选择项目时，点击另一项目改变选择')

3：
if ListView1.Selected <> nil then
AllowChange := False;

CheckBox1.Checked:=True;
注意，不要在它的Click事件中写：CheckBox1.Checked:=not CheckBox1.Checked;

我是要区分4种操作的不同，而不是要得到ItemIndex、ItemFocused、selected
的值。

这些状态好象是没办法区分的，因为listview的onchanging里只有三种状态，就是：
ctText, ctImage, ctState，具体的说明是：
ctText A change to the Caption property of the list item.
ctImage A change to the list item抯 ImageIndex property or the list view抯 image list.
ctState A change to the list item抯 Cut, Focused, or Selected property.

楼上所说的四种改变状态都是属于ctState的改变。

to chenxz:我就是想在OnChanging中区分ctState的几种不同情况，你能有什么办法吗？

你只需要判断Change为csState，然后再根据我上面写的判断就可以了。
难道不是吗？

to yzhshi：1、3如何区分。
我是要同时区分四种状态。

>>3、有选择项目时，点击原选择项目；
能详细解释一下你的需求吗？我上面给的单独对3的代码不可以吗？

我是要在选择项目时检查数据是否要保存，如用户要保存，则取消掉选择操作，
恢复原选择项目；如用户不要保存则正常选择新项目。同时在用户选择一个项目时，
显示一些项目的相关信息给用户修改。在用户改变CheckBox是要记录下来数据改变。
所以要同时区分四种状态。

procedure TForm1.ListView1Changing(Sender: TObject; Item: TListItem;
Change: TItemChange; var AllowChange: Boolean);
begin
if ctstate in [change] then
begin
if ListView1.Selected = nil then
Caption := '原来没有选择什么，让它改变吧'
else if CheckBox1.Checked then
begin
if Application.MessageBox('数据已经修改，是否继续？', '询问', 32 + mb_YesNo) = mrNo then
AllowChange := False
else
AllowChange := True
end;
end;
end;

private
{ Private declarations }
public
{ Public declarations }
end;

var
Form1 : TForm1;

implementation

var
vl_SelItem: Integer;
vl_Chk_Item: array of Boolean;

{$R *.DFM}

procedure TForm1.ListView1Changing(Sender: TObject; Item: TListItem;
Change: TItemChange; var AllowChange: Boolean);
begin
if (Item.Checked <> vl_Chk_Item[Item.Index]) then
begin
vl_Chk_Item[Item.Index] := not vl_Chk_Item[Item.Index];
ShowMessage('改变');
Exit;
end;

if vl_SelItem = -1 then
ShowMessage('原来没项目,点击一项目选中')
else
if vl_SelItem <> Item.Index then
ShowMessage('原来有项目，选中了另一项目')
else
ShowMessage('原来有项目，选中了原来同一项目');

vl_SelItem := Item.Index;
end;

procedure TForm1.FormCreate(Sender: TObject);
var
I : Integer;
l_Item : TListItem;
begin
ListView1.OnChanging := nil;

for I := 0 to 20 do
with ListView1 do
begin
l_Item := Items.Add;
l_Item.Caption := IntToStr(I);
end;

SetLength(vl_Chk_Item, ListView1.Items.Count);
for I := 0 to ListView1.Items.Count - 1 do
vl_Chk_Item := ListView1.Items.Checked;

vl_SelItem := -1;

ListView1.OnChanging := ListView1Changing;
end;

消息序列：
无选择项目，选择一个新项目。
=================================================================
OnChanging Item
Caption = 1
Focused = False
Selected = False
-----------------------------------------------------------------
ListView.Selected
Selected = nil
=================================================================
=================================================================
OnChange Item
Caption = 1
Focused = True
Selected = True
-----------------------------------------------------------------
ListView.Selected
Caption = 1
Focused = True
Selected = True
=================================================================
=================================================================
SelectItem Item
Caption = 1
Focused = True
Selected = True
-----------------------------------------------------------------
ListView.Selected
Caption = 1
Focused = True
Selected = True
=================================================================
已有选择项目，选择新项目
=================================================================
OnChanging Item
Caption = 1
Focused = True
Selected = True
-----------------------------------------------------------------
ListView.Selected
Caption = 1
Focused = True
Selected = True
=================================================================
=================================================================
OnChange Item
Caption = 1
Focused = False
Selected = True
-----------------------------------------------------------------
ListView.Selected
Caption = 1
Focused = False
Selected = True
=================================================================
=================================================================
OnChanging Item
Caption = 1
Focused = False
Selected = True
-----------------------------------------------------------------
ListView.Selected
Caption = 1
Focused = False
Selected = True
=================================================================
=================================================================
OnChange Item
Caption = 1
Focused = False
Selected = False
-----------------------------------------------------------------
ListView.Selected
Selected = nil
=================================================================
=================================================================
SelectItem Item
Caption = 1
Focused = False
Selected = False
-----------------------------------------------------------------
ListView.Selected
Selected = nil
=================================================================
=================================================================
OnChanging Item
Caption = 4
Focused = False
Selected = False
-----------------------------------------------------------------
ListView.Selected
Selected = nil
=================================================================
=================================================================
OnChange Item
Caption = 4
Focused = True
Selected = True
-----------------------------------------------------------------
ListView.Selected
Caption = 4
Focused = True
Selected = True
=================================================================
=================================================================
SelectItem Item
Caption = 4
Focused = True
Selected = True
-----------------------------------------------------------------
ListView.Selected
Caption = 4
Focused = True
Selected = True
=================================================================
选择自己
=================================================================
OnChanging Item
Caption = 1
Focused = True
Selected = True
-----------------------------------------------------------------
ListView.Selected
Caption = 1
Focused = True
Selected = True
=================================================================
=================================================================
OnChanging Item
Caption = 1
Focused = True
Selected = True
-----------------------------------------------------------------
ListView.Selected
Caption = 1
Focused = True
Selected = True
=================================================================
已有选择项目，选择无
=================================================================
OnChanging Item
Caption = 1
Focused = True
Selected = True
-----------------------------------------------------------------
ListView.Selected
Caption = 1
Focused = True
Selected = True
=================================================================
=================================================================
OnChange Item
Caption = 1
Focused = True
Selected = False
-----------------------------------------------------------------
ListView.Selected
Selected = nil
=================================================================
=================================================================
SelectItem Item
Caption = 1
Focused = True
Selected = False
-----------------------------------------------------------------
ListView.Selected
Selected = nil
=================================================================
有选择项目，选择无后，在点击空白
=================================================================
OnChanging Item
Caption = 4
Focused = True
Selected = False
-----------------------------------------------------------------
ListView.Selected
Selected = nil
=================================================================s

Check其它项目
=================================================================
OnChanging Item
Caption = 4
Focused = False
Selected = False
-----------------------------------------------------------------
ListView.Selected
Caption = 1
Focused = True
Selected = True
=================================================================
=================================================================
OnChange Item
Caption = 4
Focused = False
Selected = False
-----------------------------------------------------------------
ListView.Selected
Caption = 1
Focused = True
Selected = True
=================================================================
Check自己
=================================================================
OnChanging Item
Caption = 1
Focused = True
Selected = True
-----------------------------------------------------------------
ListView.Selected
Caption = 1
Focused = True
Selected = True
=================================================================
=================================================================
OnChange Item
Caption = 1
Focused = True
Selected = True
-----------------------------------------------------------------
ListView.Selected
Caption = 1
Focused = True
Selected = True
=================================================================

改在Click事件中自己判断解决。