unit Unit1;

interface

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

type
TForm1 = class(TForm)
Button1: TButton;
Button2: TButton;
Label1: TLabel;
Memo1: TMemo;
procedure Button1Click(Sender: TObject);
procedure Button2Click(Sender: TObject);
procedure WMPowerBroadcast(var message: TMessage); message
WM_POWERBROADCAST;
procedure FormDestroy(Sender: TObject);

private
{ Private declarations }
public
{ Public declarations }
end;
tagKBDLLHOOKSTRUCT = packed record
vkCode: DWORD; //虚拟键值
scanCode: DWORD; //扫描码值
{一些扩展标志，这个值比较麻烦，MSDN上说得也不太明白，但是
根据这个程序，这个标志值的第六位数（二进制）为1时ALT键按下为0相反。}
flags: DWORD;
time: DWORD; //消息时间戳
dwExtraInfo: DWORD; //和消息相关的扩展信息
end;
KBDLLHOOKSTRUCT = tagKBDLLHOOKSTRUCT;
PKBDLLHOOKSTRUCT = ^KBDLLHOOKSTRUCT;

//这个是低级键盘钩子的索引值，Delphi中没有，必须自己定义
const
WH_KEYBOARD_LL = 13;
//定义一个常量好和上面哪个结构中的flags比较而得出ALT键是否按下
const
LLKHF_ALTDOWN = $20;

var
Form1 : TForm1;
hhkLowLevelKybd : HHOOK;
implementation
{
功能：低级键盘钩子的回调函数，在里面过滤消息
参数：nCode 是Hook的标志
WParam 表示消息的类型
LParam 是一个指向我们在上面定义的哪个结构KBDLLHOOKSTRUCT的指针
返回值:如果不是0的话windows就把这个消息丢掉，程序就不会再收到这个消息了。
}

function LowLevelKeyboardProc(nCode: Integer;
WParam: WPARAM; LParam: LPARAM): LRESULT; stdcall;
var
fEatKeystroke : BOOL;
p : PKBDLLHOOKSTRUCT;
begin
Result := 0;
fEatKeystroke := FALSE;
p := PKBDLLHOOKSTRUCT(lParam);
//nCode值为HC_ACTION时表示WParam和LParam参数包涵了按键消息
if (nCode = HC_ACTION) then
begin
//拦截按键消息并测试是否是Ctrl+Esc、Alt+Tab、和Alt+Esc功能键。
case wParam of
WM_KEYDOWN,
WM_SYSKEYDOWN,
WM_KEYUP,
WM_SYSKEYUP:
begin

Form1.Memo1.Lines.Add(IntToStr(Integer(p.vkCode)));
{fEatKeystroke :=
((p.vkCode = VK_TAB) and ((p.flags and LLKHF_ALTDOWN) <> 0)) or // tab + alt
((p.vkCode = VK_ESCAPE) and ((p.flags and LLKHF_ALTDOWN) <> 0)) or // esc + alt
((p.vkCode = VK_ESCAPE) and ((GetKeyState(VK_CONTROL) and $8000) <> 0)) or //esc + ctrl
((p.vkCode = VK_DELETE) and ((GetKeyState(VK_CONTROL) and $8000) <> 0) and ((p.flags and LLKHF_ALTDOWN) <> 0)) or // ctrl+alt+del
(p.vkCode = VK_LWIN) or (p.vkCode = VK_RWIN) or (p.vkCode =VK_APPS) or // Win + contentMenu
((p.vkCode = VK_F4) and ((p.flags and LLKHF_ALTDOWN) <>0)); // alt + f4
}
fEatKeystroke := not
(p.vkCode = VK_F4);
end;
end;
end;

if fEatKeystroke = True then
Result := 1;
if nCode <> 0 then
Result := CallNextHookEx(0, nCode, wParam, lParam);

end;
{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
begin
//设置低级键盘钩子
if hhkLowLevelKybd = 0 then
begin
hhkLowLevelKybd := SetWindowsHookExW(WH_KEYBOARD_LL,
LowLevelKeyboardProc, Hinstance, 0);
if hhkLowLevelKybd <> 0 then
MessageBox(Handle, ‘低级键盘钩子设置成功！’, ‘提示’, MB_OK)
else
MessageBox(Handle, ‘低级键盘钩子设置失败！’, ‘提示’, MB_OK);
end
else
MessageBox(Handle, ‘低级键盘钩子已设置！’, ‘提示’, MB_OK);
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
//卸载低级键盘钩子
if hhkLowLevelKybd <> 0 then
if UnhookWindowsHookEx(hhkLowLevelKybd) <> False then
begin
MessageBox(Handle, ‘低级键盘钩子卸载成功！’, ‘提示’, MB_OK);
hhkLowLevelKybd := 0;
end
else
MessageBox(Handle, ‘低级键盘钩子卸载失败！’, ‘提示’, MB_OK)
else
MessageBox(Handle, ‘没有发现低级键盘钩子！’, ‘提示’, MB_OK);
end;

procedure TForm1.WMPowerBroadcast(var message: TMessage);
begin
// if Application.MessageBox(‘是否关闭系统？’,’警告’,MB_OKCANCEL + MB_DEFBUTTON2)<>IDOK then
// begin
message.Result := BROADCAST_QUERY_DENY; //阻止系统关闭热键
// end else Close();
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
//在Form关闭的时候检测，如果没有卸载钩子就卸载之
if hhkLowLevelKybd <> 0 then
UnhookWindowsHookEx(hhkLowLevelKybd);
end;

end.