Delphi 用DLL实现插件的简单实例

Delphi 用DLL实现插件的简单实例

这是DLL的代码  

实现代码： 

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.

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