之前偶然看到类似的软件，查询并切换CapsLock键、NumLock键按键状态的软件，就顺便查了一下相关的Delphi代码，特记之如下：

查询按键状态的过程

procedure CheckKeyState();
var
KeyState: TKeyboardState;
CapsLockState , NumLockState : Boolean;
begin
GetKeyboardState(KeyState);
CapsLockState := KeyState[VK_CAPITAL] = 1;
NumLockState  := KeyState[VK_NUMLOCK] = 1;
end;

切换CapsLock键状态的过程

procedure ToggleCapsLock;
var
KeyState: TKeyboardState;
begin
GetKeyboardState(KeyState);
if (KeyState[VK_CAPITAL] = 0) then
begin
Keybd_Event(VK_CAPITAL, 1, KEYEVENTF_EXTENDEDKEY or 0, 0);
Keybd_Event(VK_CAPITAL, 1, KEYEVENTF_EXTENDEDKEY or KEYEVENTF_KEYUP, 0);
end
else
begin
Keybd_Event(VK_CAPITAL, 0, KEYEVENTF_EXTENDEDKEY or 0, 0);
Keybd_Event(VK_CAPITAL, 0, KEYEVENTF_EXTENDEDKEY or KEYEVENTF_KEYUP, 0);
end;
end;

切换NumLock键状态的过程

procedure ToggleNumLock;
var
KeyState: TKeyboardState;
begin
GetKeyboardState(KeyState);
if (KeyState[VK_NUMLOCK] = 0) then
begin
Keybd_Event(VK_NUMLOCK, 1, KEYEVENTF_EXTENDEDKEY or 0, 0);
Keybd_Event(VK_NUMLOCK, 1, KEYEVENTF_EXTENDEDKEY or KEYEVENTF_KEYUP, 0);
end
else
begin
Keybd_Event(VK_NUMLOCK, 0, KEYEVENTF_EXTENDEDKEY or 0, 0);
Keybd_Event(VK_NUMLOCK, 0, KEYEVENTF_EXTENDEDKEY or KEYEVENTF_KEYUP, 0);
end;
end;