Invoke Java method from C++

Question

hello, I hope you can help me.
In the moment I am trying to use Global Hotkeys.
I am able to register global Hotkeys from Java in C++. My problem: I can't invoke an other java method as result of pressing my hotkey.
void OnHotKey(void *)
     printf("invoke my java method");
so I want to do a backcall to java in a c++ method. At Beginning Java registers my global Hotkeys in an c++ native method.

Answer 1

(My JNI is rusty, and the tutorial is gone),
Something like (Pusdo code, see JNI Spec: Accessing Fields and Methods ):
        JNIEnv * g_env, jobject g_obj;
     void OnHotKey(void *)
          // cut from the example posted above
          jclass cls;
          jmethodID mid;
          cls = (*env)->FindClass(env,"my.Class");
          if( cls == NULL ) {
                    return;
          mid=(*env)->GetMethodID(env, cls, "onHotKey", "()V");
          (*env)->CallVoidMethod( obj, mid );
     CHotkeyHandler hk;
     JNIEXPORT void JNICALL Java_gui_Gui_activateGlobalHotkeys
     (JNIEnv * env, jobject obj) {
          int err, id;
             hk.RemoveHandler(id = 0);
          hk.InsertHandler(MOD_CONTROL | MOD_ALT, 'A', OnHotKey, id);
          // We need this in OnHotKey
          g_env = env;
          g_obj = obj;
          err = hk.Start("calc.exe");
          if (err != CHotkeyHandler::hkheOk)
               printf("Error %d on Start()\n", err);
     JNIEXPORT void JNICALL Java_gui_Gui_deactivateGlobalHotkeys
     (JNIEnv * env, jobject obj) {
          int err = hk.Stop();
}