unit1.pas

ScaleBar比例尺；基于MapX 4.5的比例尺类。 并演示了Delphi中如何利用接口技术在DLL中封装对象。

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, MapXLib_TLB, StdCtrls, OleCtrls, IScaleBar;
type
  TForm1 = class(TForm)
    Map1: TMap;
    btnHideScaleBar: TButton;
    btnShowScaleBar: TButton;
    Button1: TButton;
    Map2: TMap;
    procedure btnHideScaleBarClick(Sender: TObject);
    procedure btnShowScaleBarClick(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
    procedure Button1Click(Sender: TObject);
  private
    FScaleBar: IScaleBarObject;
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

function ScaleBarObject: IScaleBarObject; external 'MapScaleBar.dll';

implementation

{$R *.dfm}

procedure TForm1.btnHideScaleBarClick(Sender: TObject);
begin
  FScaleBar.Hide(Map1);
  FScaleBar.Hide(Map2);
end;

procedure TForm1.btnShowScaleBarClick(Sender: TObject);
begin
  if not Assigned(FScaleBar) then
    FScaleBar := ScaleBarObject;
  FScaleBar.Show(Map1);
  FScaleBar.Show(Map2);
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  FScaleBar := nil;
end;

procedure TForm1.Button1Click(Sender: TObject);
type
  TScaleBarObject = function: IScaleBarObject;
var
  MyScaleBar: TScaleBarObject;
  ScaleBarHandle: Thandle;
begin
  {动态装载动态链接库}
  ScaleBarHandle := LoadLibrary('MapScaleBar.dll');
  try
    if ScaleBarHandle <> 0 then
      @MyScaleBar := GetProcAddress(ScaleBarHandle, 'ScaleBarObject');
    if MyScaleBar <> nil then
      MyScaleBar.Show(Map1);
      MyScaleBar.Show(Map2);
  finally
    FreeLibrary(ScaleBarHandle);
  end;
end;

end.