Re: SetWindowsHookEx not notifing me on key pressed, using JNI and C++ dll

From:

"Jean-Francois Briere" <jfbriere@gmail.com>

Newsgroups:

comp.lang.java.programmer

Date:

1 Aug 2006 15:15:36 -0700

Message-ID:

<1154470536.494586.153310@75g2000cwc.googlegroups.com>

Here is a very simple yet complete working sample of a
low level Windows keyboard hook within a Swing application.
Please try it.

//
// FrameTest.java
//
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class FrameTest extends JFrame {
    private JPanel mainPanel;
    private JTextArea mainTextArea;
    private HookTest hook;

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new FrameTest().setVisible(true);
            }
        });
    }

    FrameTest() {
        super("FrameTest");
        setSize(200, 200);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        mainPanel = new JPanel();
        mainPanel.setLayout(new BorderLayout());
        mainTextArea = new JTextArea();
        mainPanel.add(mainTextArea, BorderLayout.CENTER);
        getContentPane().add(mainPanel);
        addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent event) {
                hook.unRegisterHook();
            }
        });
        new Thread() {
            public void run() {
                hook = new HookTest();
                hook.registerHook();
            }
        }.start();
    }
}

//
// HookTest.java
//
public class HookTest {
    static {
        System.loadLibrary("HookTest");
    }

    void processKey(int key, boolean pressed) {
        System.out.println("Java: HookTest.processKey - key = " + key +
(pressed ? " pressed" : " released"));
    }

    native void registerHook();
    native void unRegisterHook();
}

//
// HookTest.h
//
#ifndef _Included_HookTest
#define _Included_HookTest

#include <jni.h>

#ifdef __cplusplus
extern "C" {
#endif

JNIEXPORT void JNICALL Java_HookTest_registerHook(JNIEnv * env, jobject
obj);

JNIEXPORT void JNICALL Java_HookTest_unRegisterHook(JNIEnv * env,
jobject obj);

#ifdef __cplusplus
}
#endif

#endif /* _Included_HookTest */

//
// HookTest.cpp
//
#include <windows.h>
#include "HookTest.h"

HINSTANCE hInst = NULL;
JavaVM * jvm = NULL;
jobject hookObj = NULL;
jmethodID processKeyID = NULL;
DWORD hookThreadId = 0;

extern "C" BOOL APIENTRY DllMain(HINSTANCE _hInst, DWORD reason, LPVOID
reserved) {
    switch (reason) {
    case DLL_PROCESS_ATTACH:
        printf("C++: DllMain - DLL_PROCESS_ATTACH.\n");
        hInst = _hInst;
        break;
    default:
        break;
    }

    return TRUE;
}

LRESULT CALLBACK LowLevelKeyboardProc(int nCode, WPARAM wParam, LPARAM
lParam) {
    JNIEnv * env;
    KBDLLHOOKSTRUCT * p = (KBDLLHOOKSTRUCT *)lParam;

    if (jvm->AttachCurrentThread((void **)&env, NULL) >= 0) {
        switch (wParam) {
        case WM_KEYDOWN:
        case WM_SYSKEYDOWN:
            printf("C++: LowLevelKeyboardProc - Key pressed\n");
            env->CallVoidMethod(hookObj, processKeyID, p->vkCode,
true);
            break;
        case WM_KEYUP:
        case WM_SYSKEYUP:
            printf("C++: LowLevelKeyboardProc - Key released\n");
            env->CallVoidMethod(hookObj, processKeyID, p->vkCode,
false);
            break;
        default:
            break;
        }
    }
    else {
        printf("C++: LowLevelKeyboardProc - Error on the attach current
thread.\n");
    }

    return CallNextHookEx(NULL, nCode, wParam, lParam);
}

void MsgLoop() {
    MSG message;

    while (GetMessage(&message, NULL, 0, 0)) {
        TranslateMessage(&message);
        DispatchMessage(&message);
    }
}

JNIEXPORT void JNICALL Java_HookTest_registerHook(JNIEnv * env, jobject
obj) {
    HHOOK hookHandle = SetWindowsHookEx(WH_KEYBOARD_LL,
LowLevelKeyboardProc, hInst, 0);

    if (hookHandle == NULL) {
        printf("C++: Java_HookTest_registerHook - Hook failed!\n");
        return;
    }
    else {
        printf("C++: Java_HookTest_registerHook - Hook successful\n");
    }

    hookObj = env->NewGlobalRef(obj);
    jclass cls = env->GetObjectClass(hookObj);
    processKeyID = env->GetMethodID(cls, "processKey", "(IZ)V");
    env->GetJavaVM(&jvm);
    hookThreadId = GetCurrentThreadId();

    MsgLoop();

    if (!UnhookWindowsHookEx(hookHandle))
        printf("C++: Java_HookTest_registerHook - Unhook failed\n");

    else
        printf("C++: Java_HookTest_registerHook - Unhook
successful\n");
}

JNIEXPORT void JNICALL Java_HookTest_unRegisterHook(JNIEnv *env,
jobject object) {
    if (hookThreadId == 0)
        return;

    printf("C++: Java_HookTest_unRegisterHook - call
PostThreadMessage.\n");
    PostThreadMessage(hookThreadId, WM_QUIT, 0, 0L);
}

Regards