Handling events from native objects in Java code - Code from Sachin Agrawal

Question

Hi All,
I�ve been studing this example in http://www.ibm.com/developerworks/java/library/j-jniobs/ , so I find it so interesting to be used on programs, but I'm just a starter programmer when we talk about JNI.
I hope that some good soul will tell me how I use it in java.
Let me explain better.
In this example, a main.exe it's the reponsible to call the entire program, java and C. I want to use this code, but, In java. Or better, I wanna know what I have to change, to call it from my Java code...
for example, I've tryed this:
package events;
import javax.swing.JFrame;
public class MouseDownListener extends JFrame implements IJMouseDownListener {
     EventSourceProxy _proxy;
     IJMouseDownListener _listener;
     public MouseDownListener(int handleEventSource) {
          _proxy = EventSourceProxy.get(handleEventSource);
          if (null == _proxy) {
               return;
          _listener = new IJMouseDownListener() {
               public void onMouseDown(int hPos, int vPos) {
                    System.out.println("In MouseDownListener.onMouseDown");
                    System.out.println("     X = " + String.valueOf(hPos));
                    System.out.println("     Y = " + String.valueOf(vPos));
          _proxy.addMouseDownListener(_listener);
     public void release() {
          _proxy.removeMouseDownListener(_listener);
          _listener = null;
          _proxy = null;
         public void onMouseDown(int x, int y){
        System.out.println(x + "-" +y );
     public static void main(String[] argv) {
          MouseDownListener listener = new MouseDownListener(0);
                listener.setVisible(true);
}but doesn�t work.
Thanks for your help!

Answer 1

Jschell Hello,
I really think that I was not very clear in my question.
Sorry about my very bad English.
In the example linked, there is a file main.cpp that starts the program:
// Defines the entry point
#include "EventSource.h"
#include "MouseDownListener.h"
#include "Jvm.h"
#include <process.h>
#include <windows.h>
void __cdecl ThreadMain(void * pSource)
     ((CEventSource *)pSource)->fireMouseDownEvent(50, 100);
     CJvm::DetachThread();
int main(int argc, char* argv[])
     CEventSource eventSource;
     CMouseDownListener listener;
     eventSource.addMouseDownListener(&listener);
     CJvm::CreateJVM(argc-1, &argv[1]);
     jobject jobj = CJvm::CreateJavaObject("events/MouseDownListener", (int)(IEventSource *)&eventSource);
     _beginthread(ThreadMain, 0, &eventSource);
     Sleep(2000);
     CJvm::ReleaseJObject(jobj);
     CJvm::DestroyJVM();
     return 0;
}And the command line to execute all the thing is
main.exe "-Djava.class.path=.\\java\\bin"
"-Djava.library.path=.\\cpp\\listener\\Debug"and the result in a dos prompt is:
In CMouseDownListener::onMouseDown
X = 50
Y = 100
In MouseDownListener.onMouseDown
X = 50
Y = 100
According to the example, this code main.cpp, calls the Java classes too:
EventSourceProxy.java, IJMouseDownListener.java, MouseDownListener.java.
But, I want to modify it so that I can start my program directly from within Java in a way that I start the program with something like
"Main java," plus the required parameters, and can thus manipulate the results obtained through the java.
In short, I wanted to translate the main.cpp for Java, so I have a main class in Java that start the program, call the listener.dll through JNI, take the position of the mouse, and return to my program in Java.
If you or someone else can help me,'ll be very grateful.
Tkd,
Dino