delphi无边框可拖动窗体

unit UFrmModless;

interface

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

type
  TFrmModeless = class(TForm)
    lblInfo: TLabel;
    btnClose: TButton;
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
    procedure FormDestroy(Sender: TObject);
    procedure btnCloseClick(Sender: TObject);
  private
    { Private declarations }
    procedure WMNCHITTEST(var Msg:TWMNCHITTEST);message WM_NCHITTEST;
  public
    { Public declarations }
    procedure CreateParams(var params: TCreateParams); override;
  end;

var
  FrmModeless: TFrmModeless;

implementation

{$R *.dfm}
procedure TFrmModeless.CreateParams(var params: TCreateParams);
begin
    inherited CreateParams(params);
    params.Style := WS_THICKFRAME or WS_POPUP or WS_BORDER;
end;

procedure TFrmModeless.WMNCHITTEST(var Msg: TWMNCHITTEST);
begin
    inherited;
    Msg.Result:=HTCaption;
end;

procedure TFrmModeless.FormClose(Sender: TObject;
  var Action: TCloseAction);
begin
    Action := caFree;
//    FrmModeless := nil;
end;

procedure TFrmModeless.FormDestroy(Sender: TObject);
begin
    FrmModeless := nil;
end;

procedure TFrmModeless.btnCloseClick(Sender: TObject);
begin
    self.Close;
end;

end.