Sample java listener and jni callback functions added

bindings/java/org/videolan/jvlc/VolumeListener.java

+package org.videolan.jvlc;
+
+public interface VolumeListener {
+
+	void volumeChanged();
+	
+}

bindings/java/src/callback-jni.cc

+/*****************************************************************************
+ * callback-jni.cc: JNI native callback functions for VLC Java Bindings
+ *****************************************************************************
+ * Copyright (C) 1998-2006 the VideoLAN team
+ *
+ * Authors: Filippo Carone <filippo@carone.org>
+ *
+ *
+ * $Id $
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111, USA.
+ *****************************************************************************/
+
+/* These are a must*/
+#include <jni.h>
+#include <vlc/libvlc.h>
+#ifdef WIN32
+#include <windows.h>
+#undef usleep
+#define usleep(var) Sleep(var/1000)
+#else
+#include <unistd.h>
+#endif
+#include <stdio.h>
+
+#include "utils.h"
+
+#include "../includes/Audio.h"
+
+static JavaVM *jvm;
+static jclass audioClass;
+static jmethodID wakeupListenersMethod;
+
+void volumeChangedCallback( libvlc_instance_t *p_instance, libvlc_event_t *event, void *user_data );
+
+
+JNIEXPORT void JNICALL Java_org_videolan_jvlc_Audio__1install_1callback( JNIEnv *env, jobject _this )
+{
+    INIT_FUNCTION ;
+    if (jvm == NULL)
+    {
+        env->GetJavaVM( &jvm );
+	audioClass = env->GetObjectClass( _this );
+	wakeupListenersMethod = env->GetStaticMethodID(audioClass, "wakeupListeners", "()V");
+    }
+
+    libvlc_callback_register_for_event( ( libvlc_instance_t* ) instance,
+					VOLUME_CHANGED,
+					volumeChangedCallback,
+					&_this,
+					exception );
+    CHECK_EXCEPTION_FREE ;
+}
+
+void volumeChangedCallback( struct libvlc_instance_t *p_instance, libvlc_event_t *event, void *user_data )
+{
+    JNIEnv *env;
+    jvm->AttachCurrentThread( ( void ** ) &env, NULL );
+
+    env->CallStaticVoidMethod( audioClass, wakeupListenersMethod);
+}