最近准备进行插件方面的编程,有经验的朋友进

Question

dll是最普遍的。
但也有些专用的，比如photoshop等。

Answer 1

好象有interface等的，我也不太清楚

Answer 2

插件程序分主程序和插件程序
主程序文件是标准的exe文件，但是程序能查找指定目录下的插件（dll），并且动态加载
而且，主程序调用插件的接口是定义好的，再开发插件是在指定接口下开发的
插件就是dll文件，但是必须提供主程序调用插件的接口，要不然主程序是不能调用插件的
用插件程序的好处就是可以方便的增加程序的功能
最著名、最成功的插件程序应该是photoshop,winamp了！给你一个例子：
主程序：unit Unit1;interfaceuses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls;type
  TPluginDescribe = Function:Boolean; stdcall;
  TPluginDrawDescribe = procedure(DC:HDC;Rect:TRect); stdcall;
  TPlugindia = procedure(); stdcall;
  TForm1 = class(TForm)
    ListBox1: TListBox;
    Button1: TButton;
    procedure FormCreate(Sender: TObject);
    procedure ListBox1DblClick(Sender: TObject);
    procedure FormPaint(Sender: TObject);
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
    procedure Button1Click(Sender: TObject);
  private
    LibHandle: HMODULE;
    DwarProc: TPluginDrawDescribe;
    dia: TPlugindia ;
    procedure LoadPlugins;
    procedure LoadPlugin(sr: TSearchRec);
    { Private declarations }
  public
    { Public declarations }
  end;var
  Form1: TForm1;implementation{$R *.DFM}procedure TForm1.FormCreate(Sender: TObject);
begin
  LibHandle:=0;
  LoadPlugins;
end;procedure TForm1.LoadPlugins;
var
  sr: TSearchRec;
  path: string;
  Found: Integer;
begin
  path := ExtractFilePath(Application.Exename);
  try
    Found := FindFirst(path + '*.DLL', 0, sr);
    while Found = 0 do
    begin
      LoadPlugin(sr);
      Found := FindNext(sr);
    end;
  finally
    FindClose(sr);
  end;
end;procedure TForm1.LoadPlugin(sr: TSearchRec);
var
  iLibHandle: HMODULE;
  pDescribeProc: TPluginDescribe;
  pDwarProc: TPluginDrawDescribe;
begin
  iLibHandle := LoadLibrary(Pchar(sr.Name));
  if iLibHandle <> 0 then
  begin
    try
      pDescribeProc := GetProcAddress(iLibHandle, 'loadpicture');
      pDwarProc := GetProcAddress(iLibHandle, 'drawpicture');
      if Assigned(pDescribeProc) and Assigned(pDwarProc) then
        ListBox1.Items.Add(sr.Name);
    finally
      FreeLibrary(iLibHandle);
    end;
  end else
    ShowMessage('loading Dll file error!');
end;procedure TForm1.ListBox1DblClick(Sender: TObject);
var pDescribeProc: TPluginDescribe;
begin
  if ListBox1.ItemIndex<>-1 then
  begin
    if LibHandle<>0 then
      FreeLibrary(LibHandle);
    DwarProc:=nil;
    LibHandle := LoadLibrary(PChar(ListBox1.Items[ListBox1.ItemIndex]));
    if LibHandle <> 0 then
    begin
      try
        pDescribeProc := GetProcAddress(LibHandle, 'loadpicture');
        if pDescribeProc then
        begin
          DwarProc := GetProcAddress(LibHandle, 'drawpicture');
          dia:= GetProcAddress(LibHandle, 'dilog');
          Invalidate;
        end;
      Except
        FreeLibrary(LibHandle);
        LibHandle:=0;
      end;
    end
    else
      ShowMessage('loading Dll file error!');
  end;
end;procedure TForm1.FormPaint(Sender: TObject);
begin
  try
    if (LibHandle<>0) and Assigned(DwarProc) then
      DwarProc(Self.Canvas.Handle,Self.ClientRect);
  Except
    if LibHandle<>0 then
    begin
      FreeLibrary(LibHandle);
      LibHandle:=0;
    end;
  end;
end;procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction);
begin
  if LibHandle<>0 then
  begin
    FreeLibrary(LibHandle);
    LibHandle:=0;
  end;
end;procedure TForm1.Button1Click(Sender: TObject);
begin
  if (LibHandle<>0) and Assigned(Dia) then
  dia;
end;end.插件dll：unit PlugInUnit; interface
Uses Graphics,extdlgs,Windows;Function loadpicture:Boolean;
procedure drawpicture(DC:HDC;Rect:TRect);export; stdcall;Var Picture:TPicture;implementationprocedure drawpicture(DC:HDC;Rect:TRect);
Var cCanvas:TCanvas;
  i,j:Integer;
begin
  if (Picture<>nil) and not Picture.Graphic.Empty then
  begin
    cCanvas:=TCanvas.Create;
    try
      cCanvas.Handle:=DC;
      cCanvas.FillRect(Rect);
      i:=0;
      While i<(Rect.Right-Rect.Left)+Picture.Width do
      begin
        j:=0;
        While j<(Rect.Bottom-Rect.Top)+Picture.Height do
        begin
          cCanvas.Draw(i,j,Picture.Graphic);
          Inc(j,Picture.Height);
        end;
        Inc(i,Picture.Width);
      end;
    finally
      cCanvas.Free;
    end;
  end;
end;Function loadpicture:Boolean;
begin
  Result:=False;
  Picture:=TPicture.Create;
  with TopenpictureDialog.Create(nil) do
  begin
    try
      if Execute then
      begin
        Picture.LoadFromFile(FileName);
        Result:=True;
      end;
    finally
      Free;
    end;
  end;
end;end.