使用钩子函数[5] - 数据传递

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.

测试窗体:

object Form1: TForm1
Left = 0
Top = 0
Caption = 'Form1'
ClientHeight = 78
ClientWidth = 271
Color = clBtnFace
Font.Charset = DEFAULT_CHARSET
Font.Color = clWindowText
Font.Height = -11
Font.Name = 'Tahoma'
Font.Style = []
OldCreateOrder = False
OnCreate = FormCreate
OnDestroy = FormDestroy
PixelsPerInch = 96
TextHeight = 13
object Button1: TButton
Left = 48
Top = 32
Width = 75
Height = 25
Caption = 'Button1'
TabOrder = 0
OnClick = Button1Click
end
object Button2: TButton
Left = 144
Top = 32
Width = 75
Height = 25
Caption = 'Button2'
TabOrder = 1
OnClick = Button2Click
end
object Timer1: TTimer
OnTimer = Timer1Timer
Left = 128
Top = 8
end
end