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: https://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