KeyHook.java

package w32keyhook;

import com.sun.jna.*;
import com.sun.jna.win32.*;
import com.sun.jna.examples.win32.*;
import com.sun.jna.examples.win32.User32.MSG;
import com.sun.jna.examples.win32.User32.LowLevelKeyboardProc;
import com.sun.jna.examples.win32.User32.KBDLLHOOKSTRUCT;
import com.sun.jna.examples.win32.W32API.LRESULT;
import com.sun.jna.examples.win32.W32API.WPARAM;
import com.sun.jna.examples.win32.W32API.HMODULE;
import com.sun.jna.examples.win32.User32.HHOOK;

/** Sample implementation of a low-level keyboard hook on W32. */
public class KeyHook {
    private static volatile boolean quit;
    private static HHOOK hhk;
    private static LowLevelKeyboardProc keyboardHook;

    public static void main(String[] args) {
        final User32 lib = User32.INSTANCE;
        HMODULE hMod = Kernel32.INSTANCE.GetModuleHandle(null);
        keyboardHook = new LowLevelKeyboardProc() {
            public LRESULT callback(int nCode, WPARAM wParam, KBDLLHOOKSTRUCT info) {
                if (nCode >= 0) {
                    switch(wParam.intValue()) {
                    case User32.WM_KEYUP:
                    case User32.WM_KEYDOWN:
                    case User32.WM_SYSKEYUP:
                    case User32.WM_SYSKEYDOWN:
                        System.err.println("in callback, key=" + info.vkCode);
                        if (info.vkCode == 81) {
                            quit = true;
                        }
                    }
                }
                return lib.CallNextHookEx(hhk, nCode, wParam, info.getPointer());
            }
        };
        hhk = lib.SetWindowsHookEx(User32.WH_KEYBOARD_LL, keyboardHook, hMod, 0);
        System.out.println("Keyboard hook installed, type anywhere, 'q' to quit");
        new Thread() {
            public void run() {
                while (!quit) {
                    try { Thread.sleep(10); } catch(Exception e) { }
                }
                System.err.println("unhook and exit");
                lib.UnhookWindowsHookEx(hhk);
                System.exit(0);
            }
        }.start();

        // This bit never returns from GetMessage
        int result;
        MSG msg = new MSG();
        while ((result = lib.GetMessage(msg, null, 0, 0)) != 0) {
            if (result == -1) {
                System.err.println("error in get message");
                break;
            }
            else {
                System.err.println("got message");
                lib.TranslateMessage(msg);
                lib.DispatchMessage(msg);
            }
        }
        lib.UnhookWindowsHookEx(hhk);
    }
}