子类化窗口辅助类NativeWindow

子类化窗口在高级开发中的重要利器。受c#中NativeWindow的启发，实现了下面这样一个简单的类，来帮助更容易地对窗口实现子类化。

unit NativeWindow;

interface

uses

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

Type

TzwNativeWindow = class

private

m_OldWinProc:FARPROC ;

m_NewWinProc:FARPROC ;

m_Handle:THandle;

protected

procedure WndProc(var Message: TMessage); virtual;

public

constructor Create;

destructor Destroy;override;

procedure AssignHandle(WndHandle:THandle);

procedure ReleaseHandle;

property Handle:THandle read m_Handle;

end;

implementation

{ TzwNativeWindow }

procedure TzwNativeWindow.AssignHandle(WndHandle: THandle);

begin

if (m_Handle<>WndHandle) then

begin

ReleaseHandle;

end;

m_Handle := WndHandle;

m_NewWinProc := MakeObjectInstance (WndProc );

m_OldWinProc := pointer(GetWindowLong (m_Handle ,GWL_WNDPROC ));

SetWindowLong(m_Handle , GWL_WNDPROC, LongInt(m_NewWinProc));

end;

constructor TzwNativeWindow.Create;

begin

m_Handle := INVALID_HANDLE_VALUE;

m_OldWinProc := nil;

m_NewWinProc := nil;

end;

destructor TzwNativeWindow.Destroy;

begin

ReleaseHandle;

inherited;

end;

procedure TzwNativeWindow.ReleaseHandle;

begin

if (m_Handle<>INVALID_HANDLE_VALUE) then

try

SetWindowLong(m_Handle,GWL_WNDPROC,LongInt(m_OldWinProc));

finally

m_Handle := INVALID_HANDLE_VALUE;

m_OldWinProc := nil;

m_NewWinProc := nil;

end;

end;

procedure TzwNativeWindow.WndProc(var Message: TMessage);

begin

with Message do

begin

Result := CallWindowProc(m_OldWinProc , m_Handle , Msg, wParam, lParam);

end;

end;

end.