I am **using same environment** as you described and working fine. Dinesh give a try:

 

    Set<String> contextNames = ad.getContextHandles();	    
    System.out.println("Context Names:"+contextNames.toString());

    String lastestContextView = (String) contextNames.toArray()[contextNames.size()-1];

    if (lastestContextView.contains("WEBVIEW_"))
    {
	    ad.context(lastestContextView);
	    System.out.println("Latest Context Name"+lastestContextView);
    }					
    Thread.sleep(5000);
    ad.context("NATIVE_APP");