delphi 开发扩展（一）

{主程序}

unit Unit2;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, DB, ADODB;

type
  TPluginName = Function:string; stdcall;
  TShowPerSN  = function(AHandle:THandle;ADOConn:TADOConnection;ACaption:String):BOOL;StdCall;

type
  TForm2 = class(TForm)
    ListBox1: TListBox;
    ADOConnection1: TADOConnection;
    procedure FormCreate(Sender: TObject);
    procedure ListBox1DblClick(Sender: TObject);
  private
    LibHandle: HMODULE;
    procedure LoadPlugins;
    procedure LoadPlugin(sr: TSearchRec);
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form2: TForm2;

implementation

{$R *.dfm}


procedure TForm2.FormCreate(Sender: TObject);
begin
  LibHandle:=0;//初始化LibHandle的值。
  LoadPlugins;//调入LoadPlugins过程。
end;

procedure TForm2.LoadPlugins;
var
  sr: TSearchRec;
  path: string;
  Found: Integer;
begin
  path := ExtractFilePath(Application.Exename);
  try
    Found := FindFirst(path + '*.DLL', 0, sr);
    while Found = 0 do//查找文件。
    begin
      LoadPlugin(sr);
      Found := FindNext(sr);
    end;
  finally
    FindClose(sr);
  end;
end;



procedure TForm2.ListBox1DblClick(Sender: TObject);
var k:TPluginName;ShowPerSN:TShowPerSN;
begin
  if ListBox1.ItemIndex<>-1 then
  begin
    if LibHandle<>0 then
      FreeLibrary(LibHandle);

    LibHandle:= LoadLibrary(Pchar(self.ListBox1.Items[self.ListBox1.ItemIndex]));
    if LibHandle <> 0 then
    begin
      try
        @k:= GetProcAddress(LibHandle, 'GetName');
        self.Text:=k;

        @ShowPerSN:= GetProcAddress(LibHandle,'GetForm');
        if not (@ShowPerSN   =   nil)   then
        begin
           ShowPerSN(application.Handle,ADOConnection1,'');
           Invalidate;
        end;
      Except
        FreeLibrary(LibHandle);
        LibHandle:=0;
      end;
    end
    else
      ShowMessage('loading Dll file error!');
  end;
end;



procedure TForm2.LoadPlugin(sr: TSearchRec);
var
  iLibHandle: HMODULE;
begin
  iLibHandle := LoadLibrary(Pchar(sr.Name));
  if iLibHandle <> 0 then
  begin
    try
       ListBox1.Items.Add(sr.Name);
    finally
      FreeLibrary(iLibHandle);
    end;
  end else
    ShowMessage('loading Dll file error!');
end;

end.