DLL的静态调用和动态调用

// ------------------------------------DLL源代码 circle.dproj -------------------------------------

library circle;

uses

SysUtils,

Classes,

Math;

{$R *.res}

function CircleArea(const radius : double) : double; stdcall;

begin

result := radius * radius * PI;

end;

exports CircleArea;

begin

end.

// ------------------------------------调用DLL--------------------------------------------------

var

Form1: TForm1;

function CircleArea(const radius : double) : double; external 'circle.dll'; // 静态调用

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);

begin

ShowMessage('static: ' + FormatFloat(',.00',CircleArea(StrToFloat(Edit1.Text))));

end;

procedure TForm1.Button2Click(Sender: TObject);

type

TCircleAreaFunc = function (const radius: double) : double; stdcall;

var

dllHandle : cardinal;

circleAreaFunc : TCircleAreaFunc;

begin

dllHandle := LoadLibrary('circle.dll'); // 动态调用

if dllHandle <> 0 then

begin

@circleAreaFunc := GetProcAddress(dllHandle, 'CircleArea');

if Assigned (circleAreaFunc) then

ShowMessage('dynamic: ' + FormatFloat(',.00',circleAreaFunc(StrToFloat(Edit1.Text))))

else

ShowMessage('"CircleArea" function not found');

FreeLibrary(dllHandle); // 释放动态库

end

else

begin

ShowMessage('circle.dll not found / not loaded');

end;

end;