用DLL实现插件的简单演示

这是DLL的代码

library MyDll;

uses
SysUtils,
Dialogs,
Classes;

procedure ShowInfo(info:PChar);stdcall;
begin
ShowMessage('您选择了【'+info+'】');
end;

function GetCaption:Pchar;
begin
Result := '中国';
end;

exports ShowInfo,
GetCaption;

{$R *.res}

begin
end.

这是调用窗体的代码
本例只使用了一个DLL，所以当有多个DLL时，需要循环DLL所在目录，依次加载DLL

unit Main;

interface

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

type
TShowInfo = procedure (info:PChar);stdcall;
TGetCaption = function : PChar;stdcall;

TForm1 = class(TForm)
Button1: TButton;
Button2: TButton;
MainMenu1: TMainMenu;
Image1: TImage;
procedure Button2Click(Sender: TObject);  private
{ Private declarations }
FHandel : THandle;     //DLL句柄
FProAddress: Pointer;  //DLL中ShowInfo的地址
showinfo: TShowInfo;   //为动态加载DLL而设
procedure LoadPlusIn;  //加载插件（DLL）
procedure ItemClick(Sender: TObject);   //自定义菜单点击事件
public
{ Public declarations }
end;

var
Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button2Click(Sender: TObject);
begin
LoadPlusIn;
end;

procedure TForm1.ItemClick(Sender: TObject);
begin
@showinfo := FProAddress;     //取地址
if @showinfo <> nil then
showinfo(PWideChar(TMenuItem(Sender).Caption));  //执行DLL中的ShowInfo
end;

procedure TForm1.LoadPlusIn;
var
getcaption: TGetCaption;
item : TMenuItem;
begin
FHandel := LoadLibrary('MyDll.dll');   //加载
if FHandel = 0 then
begin
ShowMessage('加载失败！');
Exit;
end
else
begin
@getcaption := GetProcAddress(FHandel,'GetCaption');    //取DLL中GetCaption地址
if @getcaption <> nil then
begin
item := TMenuItem.Create(MainMenu1);    //创建一个菜单
item.Caption := getcaption;             //取Caption，即调用DLL中的GetCaption
FProAddress := GetProcAddress(FHandel,'ShowInfo');  //取得DLL中ShowInfo的地址
item.OnClick := ItemClick;              //赋予菜单项的点击事件
MainMenu1.Items.Add(item);              //添加到主菜单
end;

end;
end;

end.