delphi编写与调用DLL

 delphi编写DLL

下面在delphi中编写一个简单的dll，在该dll中只有一个max函数，返回2个数中的大数(Delphi 5.0)

一、New->DLL;取名为DLL_0001,编写代码:

library dll_0001;

uses
  SysUtils,
  Classes;

{$R *.RES}

function max(x,y:integer):integer;stdcall;
begin
    if(x>y) then
     max :=x
     else
     max :=y;
end;

exports max;

begin

end.

红色部分为本身编写,这里和普通的delphi函数是同样的，只是在返回值中带个stdcall参数，而后用exports把函数导出

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Delphi调用dll

调用dll分动态调用和静态调用2中，动态调用写起来简单，安全点，动态调用复杂不少，但很灵活;

如今编写一个程序，来调用上面写的dll_0001.dll文件中的max函数

1、new一个Application，在Form中放入2个TEdit、1个TLabek；

2、

一、静态调用

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Edit1: TEdit;
    Edit2: TEdit;
    Label1: TLabel;
    procedure Edit2KeyDown(Sender: TObject; var Key: Word;
      Shift: TShiftState);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.DFM}
function max(x,y:integer):integer;stdcall;
external 'dll_0001.dll';

procedure TForm1.Edit2KeyDown(Sender: TObject; var Key: Word;
  Shift: TShiftState);
begin
if key =vk_return then
label1.Caption :=IntToStr(max(StrToInt(Edit1.text),StrToInt(edit2.text)));

end;

end.

红色代码本身添加，其中external "dll_name"中的dll_name能够是dll的绝对路径，要是该dll文件在你的搜索路径中，能够直接写文件名，可是.dll不能少写

二、动态调用,代码以下;

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Edit1: TEdit;
    Edit2: TEdit;
    Label1: TLabel;
    procedure Edit2KeyDown(Sender: TObject; var Key: Word;
      Shift: TShiftState);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.DFM}

procedure TForm1.Edit2KeyDown(Sender: TObject; var Key: Word;
  Shift: TShiftState);
type
TFunc =function(x,y:integer):integer;stdcall;
var
Th:Thandle;
Tf:TFunc;
Tp:TFarProc;

begin
if key =vk_return then
begin

Th :=LoadLibrary('dll_0001.dll');   {load dll}
if(Th  >0) then
try
Tp :=GetProcAddress(Th,PChar('max'));
if(Tp <>nil) then
begin        { begin 1}
Tf :=TFunc(Tp);
Label1.Caption :=IntToStr(
Tf(StrToInt(Edit1.text),StrToInt(Edit2.text)));
end  { end 1}
else
  ShowMessage('function max not found.');
finally
FreeLibrary(Th);
end
else
ShowMessage('dll_0001.dll not exsit.');

end;
end;

end.