Using native methods in a JavascriptObject class

I'm currently trying out my first gwt app with gwt-map library. I'm having problem accessing getLatitude() and other similar methods on ClientLocation class. I'm new to gwt and needless to say JavaScriptObject

[update] I real开发者_Python百科ized that I have to include

private native ClientLocation getUser() /*-{

  return $wnd.jsonData[0]; 
}-*/;

to access the methods. However, I'm prompted with the following error

com.google.gwt.core.client.JavaScriptException: (TypeError): Cannot read property '0' of undefined stack: TypeError: Cannot read property '0' of undefined

after executing

ClientLocation user = getUser();

How should I create an instance for ClientLocation ? Any help or ideas will be much appreciated...

gwt-map Library: http://code.google.com/p/gwt-google-apis/wiki/MapsGettingStarted

API for ClientLocation: http://gwt-google-apis.googlecode.com/svn/javadoc/maps/1.1/com/google/gwt/ajaxloader/client/ClientLocation.html

That TypeError you're seeing is JavaScript's equivalent to a NullPointerException. It's likely that the jsonData property is not defined on the host window. You can verify this by using the Chrome developer tools console or FireBug's console to evaluate window.jsonData to ensure that it is defined.

Figured it out..

ClientLocation user = AjaxLoader.getClientLocation();

Hope this will help other first timers with gwt and gwt-map