[Windows Hook] 屏蔽键盘按键

//该例程为在系统级屏蔽一些系统键、如WIN、TAB、CAP、POWER、SLEEP、HOME等！

//屏蔽组合键下面例程不适用！(比如CTRL+ESC需要在钩子函数中用(p.vkCode = VK_ESCAPE) and ((GetKeyState(VK_CONTROL) and $8000) <> 0)进行判断,也不难，这里只是举个简单的例子)

unit KeyBlocker;



interface



uses

  SysUtils, Classes, Windows, Messages;



const

  WH_KEYBOARD_LL = 13;



type

  PKBDLLHOOKSTRUCT = ^KBDLLHOOKSTRUCT;

  KBDLLHOOKSTRUCT = packed record

    vkCode: DWORD;

    scanCode: DWORD;

    flags: DWORD;

    Time: DWORD;

    dwExtraInfo: DWORD;

  end;



  TBlockKeyEvent = procedure(VirtualKey: Cardinal) of object;



  TKeyBlocker = class

  private

    FEnabled: Boolean;

    FCustomKey:Cardinal;

    FOnBlockKey: TBlockKeyEvent;

    procedure SetEnabled(const Value: Boolean);

    procedure SetCustomKey(const Value: Cardinal);

    procedure DoBlock(VirtualKey: Cardinal);

    procedure UpdateKeyBlock;

  public

    constructor Create;

    destructor  Destroy; override;

    property    CustomKey: Cardinal read FCustomKey write SetCustomKey default 0;

    property    Enabled: Boolean read FEnabled write SetEnabled default False;

    property    OnBlockKey: TBlockKeyEvent read FOnBlockKey write FOnBlockKey;

  end;



implementation



{ TKeyBlocker }



var

  KeyboardHook: HHOOK = 0;

  FKeyBlocker: TKeyBlocker = nil;//设计这一变量的作用就是能在LowLevelfunction中访问类成员变量！

//LowLevelfunction为系统回调函数，为确保在系统调用时存在，就必须把之设计为一个类函数或静态函数，使之在编译期就能生成地址，如果设计为虚函数，系统就晕了



constructor TKeyBlocker.Create;

begin

  inherited;

  FKeyBlocker := Self;

end;



destructor TKeyBlocker.Destroy;

begin

  Enabled := False;

  FKeyBlocker := nil;

  inherited;

end;



procedure TKeyBlocker.DoBlock(VirtualKey: Cardinal);

begin

  if Assigned(FOnBlockKey) then

    FOnBlockKey(VirtualKey);

end;



procedure TKeyBlocker.SetCustomKey(const Value: Cardinal);

begin

  FCustomKey := Value;

end;



procedure TKeyBlocker.SetEnabled(const Value: Boolean);

begin

  FEnabled := Value;

  UpdateKeyBlock;

end;

//核心部分

function LowLevelKeyboardFunc(nCode: INTEGER; w_Param: WPARAM;

  l_Param: LPARAM): LRESULT; stdcall;

var

  boolKey: Boolean;

  p: PKBDLLHOOKSTRUCT;

begin

  boolKey := False;

  p := nil;

  if nCode = HC_ACTION then

  begin

    case w_Param of

      WM_KEYDOWN, WM_SYSKEYDOWN, WM_KEYUP, WM_SYSKEYUP:

        begin

          p := PKBDLLHOOKSTRUCT(l_Param);

            if (p.vkCode = FKeyBlocker.FCustomKey)  then

              boolKey := True;

        end;

    end;

  end;



  if boolKey and (p <> nil) then

  begin

    FKeyBlocker.DoBlock(p.vkCode);

    Result := 1;

    Exit;

  end;



  Result := CallNextHookEx(0, nCode, w_Param, l_Param);

end;

//装载hook与卸载hook

procedure TKeyBlocker.UpdateKeyBlock;

begin

  if KeyboardHook <> 0 then Exit;

  case FEnabled of

    True:

       KeyboardHook := SetWindowsHookEx(WH_KEYBOARD_LL, LowLevelKeyboardFunc, HInstance, 0);

    False:

       UnhookWindowsHookEx(KeyboardHook); 

  end;

end;



end.

----------------------------------------------------------------

//调用程序



procedure BlockProc(VirtualKey: Cardinal);

begin

  //to do ..

end;

procedure TForm1.btn1Click(Sender: TObject);

var

  KeyBlockerTest:TKeyBlocker;

begin

  KeyBlockerTest:=TKeyBlocker.Create;

  KeyBlockerTest.CustomKey:=VK_CAPITAL;

  KeyBlockerTest.OnBlockKey:=BlockProc;

  KeyBlockerTest.Enabled:=true;

end;

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