程序内hook键盘

在程序内部hook键盘的话主要调用SetWindowsHookEx这个函数。

例子如下：用按键在image上画线。

unit Unit1;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.ExtCtrls;

type
  TForm1 = class(TForm)
    Image1: TImage;
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

  KBhook: Hhook; 
  cx, cy : integer; 

  function KeyboardHookProc(code: Integer; WordParam: Word; LongParam: LongInt):LongInt; stdcall;
   {declaring a callback}

implementation

{$R *.dfm}

function KeyboardHookProc(Code: Integer; WordParam: Word; LongParam: LongInt): LongInt;
begin
  case WordParam of
   vk_Space: 
    begin
     with Form1.Image1.Canvas do
     begin
      Brush.Color := clWhite;
      Brush.Style := bsSolid;
      FillRect(Form1.Image1.ClientRect)
     end;
    end;
   vk_Right: cx := cx+1;
   vk_Left: cx := cx-1;
   vk_Up: cy := cy-1;
   vk_Down: cy := cy+1;
  end; {case}

  If cx < 2 then cx := Form1.Image1.ClientWidth-2;
  If cx > Form1.Image1.ClientWidth -2 then cx := 2;
  If cy < 2 then cy := Form1.Image1.ClientHeight -2 ;
  If cy > Form1.Image1.ClientHeight-2 then cy := 2;

  with Form1.Image1.Canvas do
  begin
   Pen.Color := clRed;
   Brush.Color := clYellow;
   TextOut(0,0,Format('%d, %d',[cx,cy])) ;
   Rectangle(cx-2, cy-2, cx+2, cy+2) ;
  end;

  Result:=0;

end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  {Set a keyboard hook so we can hook keyboard input}
  KBHook:=SetWindowsHookEx(WH_KEYBOARD,
            {callback >} @KeyboardHookProc,
                           HInstance,
                           GetCurrentThreadId()) ;

  {put the warship in the center of the screen}
  cx := Image1.ClientWidth div 2;
  cy := Image1.ClientHeight div 2;

  Image1.Canvas.PenPos := Point(cx,cy);
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
   UnHookWindowsHookEx(KBHook) ;
end;

end.