unit UCallHwnd;interfaceuses  Classes, Messages, Windows;const  WM_USER_MSG = WM_USER + 1;type  TCallHwnd = class(TObject)  private    FHwnd: THandle;  protected    procedure DoUserMessage(var AMsg: TMessage);  public    constructor Create;    destructor Destroy; override;    //调用测试    function CallHwndTest: Boolean;  end;implementation{ TCallHwnd }function TCallHwnd.CallHwndTest: Boolean;begin  Result := PostMessage(FHwnd, WM_USER_MSG, 1, 2)end;constructor TCallHwnd.Create;begin  FHwnd := AllocateHWnd(DoUserMessage);end;destructor TCallHwnd.Destroy;begin  DeallocateHWnd(FHwnd);  inherited;end;procedure TCallHwnd.DoUserMessage(var AMsg: TMessage);begin  if AMsg.Msg = WM_USER_MSG then  begin    //AMsg.LParam 2    //AMsg.WParam 1    //do something  end  else    AMsg.Result := DefWindowProc(FHwnd, AMsg.Msg, AMsg.WPARAM, AMsg.LPARAM);end;end.