DLL的调用方法

1.定义DLL中需要调用的函数  TShowFrm = procedure(App: TApplication  参数一; Scr: TScreen  参数二 ); stdcall;（无需定义函数或过程名，只需要定义是否为过程或者函数，参数的数量及格式）；

2.定义hInstance：THandle变量，采用hInstance := LoadLibrary('Projectdll.dll')获取DLL地址；

3.定义 AFunc: Pointer;指针变量，采用Pointer(AFunc) := GetProcAddress(hInstance, PChar('ShowFrm'));获取函数地址；

4.执行函数 TShowFrm(AFunc)(Application, Screen)， 定义的函数名(函数地址)(函数需要的参数一，参数二)；

 

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unit Unit1;

interface

uses

  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants,

  System.Classes, Vcl.Graphics,

  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.ComCtrls, Vcl.ToolWin, Vcl.StdCtrls;

type

  TShowFrm = procedure(App: TApplication; Scr: TScreen); stdcall;//定义需要在DLL调用的函数或过程

type

  TForm1 = class(TForm)

    ToolBar1: TToolBar;

    ToolButton1: TToolButton;

    Edit1: TEdit;

    Button2: TButton;

    Button3: TButton;

    Button4: TButton;

    Button1: TButton;

    Button5: TButton;

    procedure Button2Click(Sender: TObject);

    procedure Button3Click(Sender: TObject);

    procedure Button4Click(Sender: TObject);

    procedure Button1Click(Sender: TObject);

    procedure Button5Click(Sender: TObject);

    procedure FormCreate(Sender: TObject);

  private

    { Private declarations }

  public

    { Public declarations }

    hInstance: THandle;//定义用来获取DLL地址的指针变量

  end;

var

  Form1: TForm1;

implementation

{$R *.DFM}

procedure TForm1.Button2Click(Sender: TObject);

begin

  try

    hInstance := LoadLibrary('Projectdll.dll');//LOAD DLL 将地址赋给DLL指针变量

    { load the library on form create as will need to know what forms are available, so they can be listed for creation. }

  except

    on e: exception do

      ShowMessage(e.Message);

  end;

end;

procedure TForm1.Button3Click(Sender: TObject);

var

  AFunc: Pointer;//定义函数过程指针

begin

  try

    Pointer(AFunc) := GetProcAddress(hInstance, PChar('ShowFrm'));//将在DLL中获取函数的地址赋给函数指针

    TShowFrm(AFunc)(Application, Screen);//将TSHOWFRM类的地址指针赋值为DLL中的地址，然后执行，（赋予参数Application, Screen）。

    { Open the child form }

  except

    on e: exception do

      ShowMessage(e.Message);

  end;

end;