用户按键时看不到消息

Question

以下java 程序调用C 中的本机方法，如果用户按下某个键，该方法应打印一条消息you pressed a key !。但是当我按下键时我看不到消息。我还检查函数SetWindowsHookEx是否返回null，但不是，它不返回null。

Java 代码：

package keylogger;

public class TestKeys {

private native void setWinHook();

public static void main(String args[]) {
    TestKeys o = new TestKeys();
    try {
        o.setWinHook();
        Thread.sleep(10000);
    } catch(Exception exc) {
        exc.printStackTrace();
    }
}

static {
    System.loadLibrary("MyHook");
}

} C 代码：

#include <stdio.h>
#include <windows.h>
#include <w32api.h>
#include "keylogger_TestKeys.h"
static HHOOK handleKeyboardHook = NULL;
HINSTANCE hInst = NULL;

static LRESULT CALLBACK LowLevelKeyboardProc(int nCode, WPARAM wParam, LPARAM lParam) {
  printf("You pressed a key !\n");
  return CallNextHookEx(handleKeyboardHook, nCode, wParam, lParam);
}

void Java_keylogger_TestKeys_setWinHook
 (JNIEnv *env, jobject obj) {
hInst = GetModuleHandle(NULL); // include or exclude,i don't see the result
handleKeyboardHook = SetWindowsHookEx(WH_KEYBOARD_LL, LowLevelKeyboardProc,NULL, 0);
if(handleKeyboardHook==NULL) {
    printf("Is Null");
} else {
    printf("Is not Null");
}
printf("Inside fucntion setWinHook !");
}

/*int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
 printf("Hello World !");
 handleKeyboardHook = SetWindowsHookEx(WH_KEYBOARD_LL, LowLevelKeyboardProc, hInstance, 0);
 if(handleKeyboardHook==NULL) {
  printf("Is Null");
 } else {
    printf("Is not Null");
   }
 MSG msg;
 while(GetMessage(&msg, NULL, 0, 0))
 {
   TranslateMessage(&msg);
   DispatchMessage(&msg);
 }
 return msg.wParam;
}*/

我看到的唯一输出是 Is not NullInside fucntion setWinHook ！

问题出在哪里？

我应该怎么做才能让这个程序在我按下键时返回消息。 我看到的唯一输出是：Inside function setWinHook !

注意：

如果上面的程序在别人的机器上运行，请注明。

输出图片：

我在按键时没有看到任何消息。程序仅在 10 秒后退出而不显示消息。

Answer 1

您不能简单地声明一个本地 HINSTANCE 变量并将其传递给函数。 HINSTANCE 是应用程序实例的句柄，换句话说，是一个必须指向有效位置的指针。您需要使用属于您自己的应用程序的 HINSTANCE。

我的 Windows API 有点生疏，但我相信您可以通过 GetModuleHandle() 来做到这一点。 所以：

void Java_keylogger_TestKeys_setWinHook
     (JNIEnv *env, jobject obj) {
   HINSTANCE hInst;
   hInst = GetModuleHandle(null);
   handleKeyboardHook = SetWindowsHookEx(WH_KEYBOARD_LL, LowLevelKeyboardProc, hInst, 0);
   printf("Inside function setWinHook !");
 }

您的 Java goo 也很可能在某个对象中隐藏了 HINSTANCE。

Answer 2

查看Java Global(low level) Keyboard/Mouse Hook

我尝试自己写一个，但对我来说似乎有太多未知的细节（JNI、HOOKS、线程问题等）

Answer 3

HHOOK 变量需要在共享数据段内声明。 在这里检查它是如何完成的 - http://www.codeproject.com/Articles/5002/Mousey-Roll-Over-and-Park

Answer 4

您需要一个GetMessage/PeekMessage 循环，以便您的键盘挂钩接收任何事件。有关 Windows 上键盘挂钩的 Java 实现，请参阅JNA Keyboard Hook in Windows，或在 JNA 项目中执行相同功能的贡献包 (https://github.com/twall/jna/tree/master/contrib/w32keyhook)。

Answer 5

肯定有更好的方法来实现这一点。这里DllMain 在创建线程后被多次调用，这对我来说似乎不对。我不确定这是否合法！ C 代码启动一个新线程来实现 keycatcher。

C 代码：

#include <stdio.h>
#include <windows.h>
#include <w32api.h>
#include "keylogger_TestKeys.h"

static HHOOK handleKeyboardHook = NULL;
HINSTANCE hInst = NULL;
static DWORD hookThreadId = 0;
static HANDLE hookThreadHandle = NULL;
BOOL WINAPI installHook(HINSTANCE hinstDLL, DWORD fwdReason, LPVOID lpvReserved);
static int i = 0;

static LRESULT CALLBACK LowLevelKeyboardProc(int nCode, WPARAM wParam, LPARAM lParam) {

  printf("You pressed the key !");
  return CallNextHookEx(handleKeyboardHook, nCode, wParam, lParam);
}


BOOL WINAPI DllMain( HINSTANCE hinstDLL, DWORD fdwReason, LPVOID lpvReserved) {
 if(hookThreadHandle==NULL) {
    printf("hookThreadHandle is NULL\n");
    LPTHREAD_START_ROUTINE lpStartAddress = &installHook;
    hookThreadHandle = CreateThread(NULL, 0, lpStartAddress, NULL, 0, &hookThreadId);
 }
}

BOOL WINAPI installHook(HINSTANCE hinstDLL, DWORD fwdReason, LPVOID lpvReserved) {
// printf("From installHook : %u",fwdReason);
printf("count : %d\n",i++);
handleKeyboardHook = SetWindowsHookEx(WH_KEYBOARD_LL, LowLevelKeyboardProc, hinstDLL, 0);
MSG msg;

while(GetMessage(&msg, NULL, 0, 0))
{
  TranslateMessage(&msg);
  DispatchMessage(&msg);
}
return msg.wParam;
}

void Java_keylogger_TestKeys_unregisterWinHook
 (JNIEnv *env, jobject obj) {
 // should have stopped the thread before unhooking
 if(handleKeyboardHook != NULL) {
    UnhookWindowsHookEx(handleKeyboardHook);
 }
}

void Java_keylogger_TestKeys_stopNativeThread // stop the native thread
  (JNIEnv *env, jobject obj) {
    PostThreadMessage(hookThreadId, WM_QUIT, (WPARAM) NULL, (LPARAM) NULL);
    WaitForSingleObject(hookThreadHandle, 5000);
}

Java 代码：

package keylogger;

public class TestKeys {
private static int i = 0;
private native void setWinHook();
private native void unregisterWinHook();
private native void createWinThread();
private native void stopNativeThread();

public static void main(String args[]) {
    TestKeys o = new TestKeys();
    try {
        Thread.sleep(5000);
    }catch(Exception exc) {
        exc.printStackTrace();
    }
   o.stopNativeThread();
   o.unregisterWinHook();
   System.out.println("Native thread stopped and Hook unregistered !");

   try {
        Thread.sleep(3000); // Now you won't see the message : you pressed the key 
    }catch(Exception exc) {
        exc.printStackTrace();
    }
}

static {
    System.loadLibrary("MyHook");
}
}

我启动java程序并调用DLLMain。