capture a column resize event in a TListView?

下面这个控件可以做到：

{

 Question:

 How do I capture a column resize event in TListView, the OnResize

 only works when the ListView is changed?

 Answer:

 The event can be added with a bit of work. See the custom TListview derivative

 below. It has 3 new events:

 OnColumnResize, OnBeginColumnResize, OnEndColumnResize

}

unit PBExListview ;

interface

uses

 Windows , Messages , SysUtils , Classes , Graphics , Controls , Forms ,

 Dialogs , ComCtrls ;

type

 TLVColumnResizeEvent = procedure ( Sender : TCustomListview ;

   columnindex : Integer ;

   columnwidth : Integer ) of object ;

 TPBExListview = class ( TListview )

  private

   FBeginColumnResizeEvent : TLVColumnResizeEvent ;

   FEndColumnResizeEvent : TLVColumnResizeEvent ;

   FColumnResizeEvent : TLVColumnResizeEvent ;

  protected

    procedure DoBeginColumnResize ( columnindex , columnwidth : Integer );

      virtual ;

    procedure DoEndColumnResize ( columnindex , columnwidth : Integer );

      virtual ;

    procedure DoColumnResize ( columnindex , columnwidth : Integer );

      virtual ;

    procedure WMNotify ( var Msg : TWMNotify ); message WM_NOTIFY ;

    function FindColumnIndex ( pHeader : pNMHdr ): Integer ;

    function FindColumnWidth ( pHeader : pNMHdr ): Integer ;

    procedure CreateWnd ; override ;

  published

    property OnBeginColumnResize : TLVColumnResizeEvent

      read FBeginColumnResizeEvent write FBeginColumnResizeEvent ;

    property OnEndColumnResize : TLVColumnResizeEvent

      read FEndColumnResizeEvent write FEndColumnResizeEvent ;

    property OnColumnResize : TLVColumnResizeEvent

      read FColumnResizeEvent write FColumnResizeEvent ;

  end ;

procedure Register ;

implementation

uses CommCtrl ;

procedure Register ;

begin

 RegisterComponents ( 'PBGoodies' , [ TPBExListview ]);

end ;

procedure TPBExListview . DoBeginColumnResize ( columnindex , columnwidth : Integer );

begin

  if Assigned ( FBeginColumnResizeEvent ) then

   FBeginColumnResizeEvent ( Self , columnindex , columnwidth );

end ;

procedure TPBExListview . DoEndColumnResize ( columnindex , columnwidth : Integer );

begin

  if Assigned ( FEndColumnResizeEvent ) then

   FEndColumnResizeEvent ( Self , columnindex , columnwidth );

end ;

procedure TPBExListview . DoColumnResize ( columnindex , columnwidth : Integer );

begin

  if Assigned ( FColumnResizeEvent ) then

   FColumnResizeEvent ( Self , columnindex , columnwidth );

end ;

function TPBExListview . FindColumnIndex ( pHeader : pNMHdr ): Integer ;

var

 hwndHeader         : HWND ;

 iteminfo           : THdItem ;

 ItemIndex         : Integer ;

 buf               : array [ 0 .. 128 ] of Char ;

begin

 Result := - 1 ;

 hwndHeader := pHeader ^. hwndFrom ;

 ItemIndex := pHDNotify ( pHeader )^. Item ;

 FillChar ( iteminfo , SizeOf ( iteminfo ), 0 );

 iteminfo . Mask := HDI_TEXT ;

 iteminfo . pszText := buf ;

 iteminfo . cchTextMax := SizeOf ( buf ) - 1 ;

 Header_GetItem ( hwndHeader , ItemIndex , iteminfo );

  if CompareStr ( Columns [ ItemIndex ]. Caption , iteminfo . pszText ) = 0 then

   Result := ItemIndex

  else

  begin

    for ItemIndex := 0 to Columns . Count - 1 do

      if CompareStr ( Columns [ ItemIndex ]. Caption , iteminfo . pszText ) = 0 then

      begin

       Result := ItemIndex ;

       Break ;

      end ;

  end ;

end ;

procedure TPBExListview . WMNotify ( var Msg : TWMNotify );

begin

  inherited ;

  case Msg . NMHdr ^. code of

   HDN_ENDTRACK :

     DoEndColumnResize ( FindColumnIndex ( Msg . NMHdr ),

       FindColumnWidth ( Msg . NMHdr ));

   HDN_BEGINTRACK :

     DoBeginColumnResize ( FindColumnIndex ( Msg . NMHdr ),

       FindColumnWidth ( Msg . NMHdr ));

   HDN_TRACK :

     DoColumnResize ( FindColumnIndex ( Msg . NMHdr ),

       FindColumnWidth ( Msg . NMHdr ));

  end ;

end ;

procedure TPBExListview . CreateWnd ;

var

 wnd               : HWND ;

begin

  inherited ;

 wnd := GetWindow ( Handle , GW_CHILD );

 SetWindowLong ( wnd , GWL_STYLE ,

   GetWindowLong ( wnd , GWL_STYLE ) and not HDS_FULLDRAG );

end ;

function TPBExListview . FindColumnWidth ( pHeader : pNMHdr ): Integer ;

begin

 Result := - 1 ;

  if Assigned ( PHDNotify ( pHeader )^. pItem ) and

    (( PHDNotify ( pHeader )^. pItem ^. mask and HDI_WIDTH ) <> 0 ) then

   Result := PHDNotify ( pHeader )^. pItem ^. cxy ;

end ;

end .