main.pas

《Kylix程序设计》一书中附带的例程源代码

unit Main;

interface

uses
  SysUtils, Types, Classes, Variants, QGraphics, QControls, QForms, QDialogs,
  QStdCtrls, QExtCtrls;

type
  TFrmMain = class(TForm)
    BtnShow: TButton;
    RadGrpClassType: TRadioGroup;
    procedure BtnShowClick(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  FrmMain: TFrmMain;

implementation

uses Shapes;

{$R *.xfm}

procedure TFrmMain.BtnShowClick(Sender: TObject);
var
  X, Y: Integer;
  str: string;
  Point, ToPoint: TPoint;
  Rect: TRect;
  Shape: TGeoShape;
begin
  X := 10;
  Y := 10;

  case RadGrpClassType.ItemIndex of
    0: // TGeoShape
    begin
      Shape := TGeoShape.Create();  // Error. Constructing instance of 'TGeoShape' containing abstract methods
      Shape.Draw( Canvas );
      FreeAndNil( Shape );
    end;
    1: // TGeoPoint
    begin
      Point.X := 10;
      Point.Y := 50;
      Shape := TGeoPoint.Create();
      TGeoPoint( Shape ).SetValue( Point );
      Shape.Draw( Canvas );
      FreeAndNil( Shape );
    end;
    2: // TGeoLine
    begin
      Point.X := 10;
      Point.Y := 50;
      ToPoint.X := 200;
      ToPoint.Y := 50;
      Shape := TGeoLine.Create();
      TGeoLine( Shape ).SetValue( Point, ToPoint );
      Shape.Draw( Canvas );
      FreeAndNil( Shape );
    end;
    3: // TGeoRect
    begin
      Rect.Left := 10;
      Rect.Top := 10;
      Rect.Right := 200;
      Rect.Bottom := 200;
      Shape := TGeoRect.Create();
      TGeoRect( Shape ).SetValue( Rect );
      Shape.Draw( Canvas );
      FreeAndNil( Shape );
    end;
  end;
end;

end.