com - FocusChangedEventHandler in java -

i trying monitor ui element focus change using iuiautomationfocuschangedeventhandler.

tried understand seems give me illegalargumentexception: not proxy instance.

could please help/guide me it?

thanks in advance.

attached code.

in main.java

automation.addfocuschangedeventhandler(null, new focuschangedeventhandler()); 

focuschangedeventhandler.java

public class focuschangedeventhandler implements iuiautomationfocuschangedeventhandler {      public void dispose() {         // todo auto-generated method stub           }      public <t extends iunknown> t queryinterface(class<? extends iunknown> cominterface) {         // todo auto-generated method stub         return null;     }      public int addref() {         // todo auto-generated method stub         return 0;     }      public int release() {         // todo auto-generated method stub         return 0;     }      public void handlefocuschangedevent(iuiautomationelement sender) {         // todo auto-generated method stub     } } 

stack trace:

exception in thread "main" java.lang.illegalargumentexception: not proxy instance @ java.lang.reflect.proxy.getinvocationhandler(unknown source) @ net.java.dev.jna.jna.comobject.prepareargs(comobject.java:213) @ net.java.dev.jna.jna.comobject.invokevoidcom(comobject.java:379) @ net.java.dev.jna.jna.comobject.invoke(comobject.java:637) @ com.sun.proxy.$proxy4.addfocuschangedeventhandler(unknown source) @ net.java.dev.jna.jna.test.othermethod(test.java:47) @ net.java.dev.jna.jna.test.main(test.java:12)