mainfrm.pas

《Delphi 7经典问题解析》源代码 第一到七章 基础篇源程序 应用篇源程序

unit MainFrm;

interface

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

type
  //定义DLL中引出的过程类型
  TShowDLLForm = procedure(aHandle: THandle); stdcall;
  EDLLError = class(Exception);
  TFrmMain = class(TForm)
    btnShowModal: TButton;
    btnShow: TButton;
    procedure btnShowModalClick(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure btnShowClick(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
  private
  //指向加载后DLL句柄
    DLLHandle: THandle;
    { Private declarations }
  public
    { Public declarations }
  end;

var
  FrmMain: TFrmMain;
implementation

{$R *.dfm}

//窗体创建时，加载DLL
procedure TFrmMain.FormCreate(Sender: TObject);
begin
  DLLHandle := LoadLibrary('..\5-1\DLLShowForm.dll');
  {如果DLLHandle为0，代表加载DLL失败}
  if DLLHandle = 0 then
    raise EDLLError.Create('不能加载DLLShowForm.dll');
end;

//窗体释放时，卸载DLL
procedure TFrmMain.FormDestroy(Sender: TObject);
begin
  FreeLibrary(DLLHandle);
end;

//模式显示窗口
procedure TFrmMain.btnShowModalClick(Sender: TObject);
var
  ShowDLLModalForm: TShowDLLForm;
begin
  {链接DLL中的输出函数，以被调用}
  if (@ShowDLLModalForm = nil) then
    RaiseLastWin32Error;
  ShowDLLModalForm(Application.Handle);
end;

//非模式显示窗口
procedure TFrmMain.btnShowClick(Sender: TObject);
var
  ShowDLLForm: TShowDLLForm;
begin
  @ShowDLLForm := GetProcAddress(DLLHandle, 'ShowDLLForm');
  if (@ShowDLLForm = nil) then
    RaiseLastWin32Error;
  ShowDLLForm(Application.Handle);
end;

end.