使用钩子函数[5] - 数据传递

使用钩子函数[5] - 数据传递2009-12-10 博客园万一前言: 博友 "鹏" 来信探讨关于钩子的问题, 核心困难是: dll 中的数据如何传递出来. 在接下来的两个例子中探讨这个问题.

本例建立一个全局的鼠标钩子, 然后把鼠标的相关信息通过一个自定义的 GetInfo 函数传递给调用钩子的程序.

为了方便测试, 提供一个源码下载吧: http://files.cnblogs.com/del/MouseHook_1.rar

本例效果图:

DLL 文件:

library MyHook;

uses
SysUtils,
Windows,
Messages,
Classes;

{$R *.res}

var
hook: HHOOK;
info: string;

function GetInfo: PChar;
begin
Result := PChar（info）;
end;

function MouseHook（nCode: Integer; wParam: WPARAM; lParam: LPARAM）: LRESULT; stdcall;
begin
case wParam of
WM_MOUSEMOVE  : info := "鼠标位置";
WM_LBUTTONDOWN : info := "按下";
WM_LBUTTONUp  : info := "放开";
end;
info := Format（"%s: %d,%d", [info, PMouseHookStruct（lParam）^.pt.X, PMouseHookStruct（lParam）^.pt.Y]）;
{此信息可通过 GetInfo 函数从外部提取}

Result := CallNextHookEx（hook, nCode, wParam, lParam）;
end;

function SetHook: Boolean; stdcall;
const
WH_MOUSE_LL =14; {Delphi 少给了两个常量: WH_KEYBOARD_LL = 13; WH_MOUSE_LL = 14; 需要时自己定义}
begin
hook := SetWindowsHookEx（WH_MOUSE_LL, @MouseHook, HInstance, 0）; {WH_MOUSE 只是线程级的}
Result := hook <> 0;
end;

function DelHook: Boolean; stdcall;
begin
Result := UnhookWindowsHookEx（hook）;
end;

exports SetHook, DelHook, MouseHook, GetInfo;
begin
end.

测试代码:

unit Unit1;

interface

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

type
TForm1 = class（TForm）
Button1: TButton;
Button2: TButton;
Timer1: TTimer;
procedure FormCreate（Sender: TObject）;
procedure Button1Click（Sender: TObject）;
procedure Button2Click（Sender: TObject）;
procedure Timer1Timer（Sender: TObject）;
procedure FormDestroy（Sender: TObject）;
end;

function SetHook: Boolean; stdcall;
function DelHook: Boolean; stdcall;
function GetInfo: PChar; stdcall;

var
Form1: TForm1;

implementation

{$R *.dfm}

function SetHook; external "MyHook.dll";
function DelHook; external "MyHook.dll";
function GetInfo; external "MyHook.dll";

procedure TForm1.Button1Click（Sender: TObject）;
begin
SetHook;
Timer1.Enabled := True;
end;

procedure TForm1.Button2Click（Sender: TObject）;
begin
Timer1.Enabled := False;
DelHook;
end;

procedure TForm1.FormCreate（Sender: TObject）;
begin
Button1.Caption := "安装钩子";
Button2.Caption := "载卸钩子";
Timer1.Interval := 100;
Timer1.Enabled := False;
FormStyle := fsStayOnTop; {为了测试, 让窗口一直在前面}
end;

procedure TForm1.FormDestroy（Sender: TObject）;
begin
DelHook;
end;

procedure TForm1.Timer1Timer（Sender: TObject）;
begin
Text := GetInfo;
end;

end.