插件的编写与应用

应用程序预留接口，通过插件扩展功能，有时候很方便，亦可作为程序升级一种方式。

 

插件的应用原理：
      1、独立的功能模块可封装成独立的动态库，如本例中的两个插件就是两个动态库，每个插件的动态库都有统一规定的接口，以便应用程序调用，本例中的ShowPlugin, GetCaption便是这种接口，其中ShowPlugin用于显示插件的窗口，GetCaption用于显示在调用插件应用程序的菜单，另外之所以单独留有此函数也是因为菜单显示在先，插件显示（调用ShowPlugin）在后。
      2、应用程序端主程序创建时，动态载入插件。先是扫描应用程序目录及子目录下.dll文件，然后调用库文件的相关函数获取信息，并根据信息动态创建菜单，菜单的Onclick事件对应插件Dll文件中的ShowPlugin，最后释放资源。

 

程序效果图及代码如下：

1、主程序Plugins菜单为插件的母菜单

 

 

2、已经装载的插件1

 

 

3、已经装载的插件2

 

 

4、插件1代码

library Plugin1;{ Important note about DLL memory management: ShareMem must be the first unit in your library's USES clause AND your project's (select Project-View Source) USES clause if your DLL exports any procedures or functions that pass strings as parameters or function results. This applies to all strings passed to and from your DLL--even those that are nested in records and classes. ShareMem is the interface unit to the BORLNDMM.DLL shared memory manager, which must be deployed along with your DLL. To avoid using BORLNDMM.DLL, pass string information using PChar or ShortString parameters. }uses SysUtils, Classes, Plugin1Unit in 'Plugin1Unit.pas' {Plugin1Frm};{$R *.res}//输出exports ShowPlugin, GetCaption;beginend.

 

 unit Plugin1Unit;interfaceuses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls, Buttons;type TPlugin1Frm = class(TForm) Label1: TLabel; BitBtn1: TBitBtn; procedure BitBtn1Click(Sender: TObject); private { Private declarations } public { Public declarations } end;var Plugin1Frm: TPlugin1Frm;//定义ShowPlugin,用于打开本窗体function ShowPlugin(AHandle: THandle; ACaption: string): Boolean; Stdcall;//输出标题，供应用程序调用本插件显示function GetCaption: PChar; Stdcall;implementation{$R *.dfm}{==================================================================函数名：ShowPlugin作者：GavinPan日期：2009-10-21功能：打开显示本窗体输入参数：AHandle 加载调用插件应用程序句柄；ACaption 给窗体标题赋值返回值：成功与否修改记录：===================================================================}function ShowPlugin(AHandle: THandle; ACaption: string): Boolean;var Plugin1Frm: TPlugin1Frm;begin Result := True; try //传递应用程序地址 Application.Handle := AHandle; //创建窗体 Plugin1Frm := TPlugin1Frm.Create(Application); try //给窗体标题赋值 Plugin1Frm.Caption := ACaption; //模式显示窗体 Plugin1Frm.ShowModal; finally Plugin1Frm.Free; end; except Result := False; end;end;{==================================================================函数名：GetCaption作者：GavinPan日期：2009-10-21功能：输出标题输入参数：无返回值：标题名称修改记录：===================================================================}function GetCaption: PChar; Stdcall;begin Result := '示例插件1';end;procedure TPlugin1Frm.BitBtn1Click(Sender: TObject);begin Close;end;end.

 

5、插件2代码

 library Plugin2;{ Important note about DLL memory management: ShareMem must be the first unit in your library's USES clause AND your project's (select Project-View Source) USES clause if your DLL exports any procedures or functions that pass strings as parameters or function results. This applies to all strings passed to and from your DLL--even those that are nested in records and classes. ShareMem is the interface unit to the BORLNDMM.DLL shared memory manager, which must be deployed along with your DLL. To avoid using BORLNDMM.DLL, pass string information using PChar or ShortString parameters. }uses SysUtils, Classes, Plugin2Unit2 in 'Plugin2Unit2.pas' {Plugin2Frm};{$R *.res}//输出exports ShowPlugin, GetCaption;beginend.

 

unit Plugin2Unit2;interfaceuses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls, Buttons;type TPlugin2Frm = class(TForm) Plugin2Frm: TBitBtn; BitBtn2: TBitBtn; Edit1: TEdit; Edit2: TEdit; Edit3: TEdit; Label1: TLabel; Label2: TLabel; Label3: TLabel; procedure Plugin2FrmClick(Sender: TObject); procedure BitBtn2Click(Sender: TObject); private { Private declarations } public { Public declarations } end;var Plugin2Frm: TPlugin2Frm;//定义ShowPlugin,用于打开本窗体function ShowPlugin(AHandle: THandle; ACaption: string): Boolean; Stdcall;//输出标题，供应用程序调用本插件显示function GetCaption: PChar; Stdcall;implementation{$R *.dfm}{==================================================================函数名：ShowPlugin作者：GavinPan日期：2009-10-21功能：打开显示本窗体输入参数：AHandle 加载调用插件应用程序句柄；ACaption 给窗体标题赋值返回值：成功与否修改记录：===================================================================}function ShowPlugin(AHandle: THandle; ACaption: string): Boolean;var Plugin2Frm: TPlugin2Frm;begin Result := True; try //传递应用程序地址 Application.Handle := AHandle; //创建窗体 Plugin2Frm := TPlugin2Frm.Create(Application); try //给窗体标题赋值 Plugin2Frm.Caption := ACaption; //模式显示窗体 Plugin2Frm.ShowModal; finally Plugin2Frm.Free; end; except Result := False; end;end;{==================================================================函数名：GetCaption作者：GavinPan日期：2009-10-21功能：输出标题输入参数：无返回值：标题名称修改记录：===================================================================}function GetCaption: PChar; Stdcall;begin Result := '示例插件2';end;procedure TPlugin2Frm.BitBtn2Click(Sender: TObject);begin Close;end;procedure TPlugin2Frm.Plugin2FrmClick(Sender: TObject);begin Edit3.Text := IntToStr(StrToInt(Edit1.Text) + StrToInt(Edit2.Text));end;end.

 

6、调用插件应用程序代码

unit Main;interfaceuses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, Menus;type TMainFrm = class(TForm) MainMenu1: TMainMenu; File1: TMenuItem; Edit1: TMenuItem; Search1: TMenuItem; N_Plugins: TMenuItem; N11: TMenuItem; N21: TMenuItem; procedure FormCreate(Sender: TObject); procedure FormDestroy(Sender: TObject); private //初始化插件 ，也就装载插件，并在菜单提供调用 procedure LoadPlugIns; //插件菜单点击事件 procedure PlugInsClick(Sender: TObject); //释放插件 procedure FreePlugIns; public { Public declarations } end;//查找文件，并存于Files中procedure SearchFileExt(const Dir, Ext: string; Files: TStrings);var MainFrm: TMainFrm;implementation{$R *.dfm}{ TMainFrm }type //定义接口函数类型 TShowPlugin = function(AHandle: THandle; ACaption: string): Boolean; Stdcall; TGetCaption = function: Pchar; StdCall; //定义TTestPlugIn类，存放caption,Address,call等信息 TTestPlugIn = class Caption: string; //存取加载后，GetCaption返回的标题 Address: THandle; //存取加载DLL的句柄 Call: Pointer; //存取ShowPlugin接口函数句柄 end;var ShowPlugin: TShowPlugin; //声明接口函数类型 Plugins: TList; //每一个DLL加载后的相关信息存于此列表 StopSearch: Boolean; //查询文件开关{==================================================================函数名：SearchFileExt作者：GavinPan日期：2009-10-21功能：查找文件，并存于Files中输入参数：Dir 文件路径，即所在文件夹；Ext 文件扩展名； Files 文件列表，符合条件的文件存入此列表返回值：无修改记录：附： //TSearchRec 结构是内涵文件大小、名称、属性与时间等信息 //TSearchRec 中的属性是一个整数值, 可能的值有: //faReadOnly 1 只读文件 //faHidden 2 隐藏文件 //faSysFile 4 系统文件 //faVolumeID 8 卷标文件 //faDirectory 16 目录文件 //faArchive 32 归档文件 //faAnyFile 63 任意文件 //faSymLink 64 链接文件===================================================================}procedure SearchFileExt(const Dir, Ext: string; Files: TStrings);var Found: TSearchRec; Sub: string; i: Integer; Dirs: TStrings; Finished: Integer;begin StopSearch := False; Dirs := TStringList.Create; Finished := FindFirst(Dir + '*.*', 63, Found); //如果Finished = 0找到一个 并且 停止开关不为真 while (Finished = 0) and not (StopSearch) do begin if (Found.Name[1] <> '.') then begin if (Found.Attr and faDirectory = faDirectory) then Dirs.Add(Dir + Found.Name) //Add to the directories list. else if Pos(UpperCase(Ext), UpperCase(Found.Name)) > 0 then Files.Add(Dir + Found.Name); end; Finished := FindNext(Found); end; FindClose(Found); //查询下一级目录 如果不查寻可将StopSearch置为真 if not StopSearch then for i := 0 to Dirs.Count - 1 do SearchFileExt(Dirs[i] + '/', Ext, Files); Dirs.Free;end;//初始化插件 ，也就装载插件，并在菜单提供调用procedure TMainFrm.LoadPlugIns;var Files: TStrings; //存放插件的文件路径列表 i: Integer; TestPlugIn: TTestPlugIn; //每个插件的实例 NewMenu: TMenuItem; //菜单Item GetCaption: TGetCaption;begin Files := TStringList.Create; Plugins := TList.Create; //查找指定目录下的.dll文件，并存于Files对象中 SearchFileExt(ExtractFilepath(Application.Exename), '.dll', Files); //加载查找到的DLL for i := 0 to Files.Count - 1 do begin //插件实例 TestPlugIn := TTestPlugIn.Create; //载入插件动态库 TestPlugIn.Address := LoadLibrary(PChar(Files[i])); if TestPlugIn.Address = 0 then raise Exception.Create('装载' + PChar(Files[i]) + '失败'); try //GetCaption接口函数句柄 @GetCaption := GetProcAddress(TestPlugIn.Address, 'GetCaption'); TestPlugIn.Caption := GetCaption; //ShowDLLForm接口函数句柄 TestPlugIn.Call := GetProcAddress(TestPlugIn.Address, 'ShowPlugin'); //增加到Plugins列表 PlugIns.Add(TestPlugIn); //创建菜单，并将菜单标题，Onclick事件赋值 NewMenu := TMenuItem.Create(Self); NewMenu.Caption := TestPlugIn.Caption; NewMenu.OnClick := PlugInsClick; NewMenu.Tag := i; //增加到应用程序菜单中 N_plugins.Add(NewMenu); except raise Exception.Create('初始化失败'); end; end; Files.Free;end;//插件菜单点击事件procedure TMainFrm.PlugInsClick(Sender: TObject);begin //根据菜单的tag属性对应函数调用的地址 @ShowPlugin := TTestPlugIn(PlugIns[TMenuItem(Sender).Tag]).Call; //执行showDllForm函数 if not ShowPlugin(application.Handle, TTestPlugIn(PlugIns[TMenuItem(Sender).Tag]).caption) then showmessage('打开窗体错误');end;//释放插件procedure TMainFrm.FormCreate(Sender: TObject);begin LoadPlugIns;end;procedure TMainFrm.FormDestroy(Sender: TObject);begin FreePlugins;end;procedure TMainFrm.FreePlugIns;var i: Integer;begin //将加载的插件全部释放 for i := 0 to PlugIns.Count - 1 do begin //释放装载的插件动态库 FreeLibrary(TTestPlugIn(PlugIns[i]).Address); end; //释放plugIns对象 PlugIns.Free;end;end.