code: static void writeTracker(JSONWriter writer, Tracker tracker)
  			throws JSONException {
  		writer.key("id");
  		writer.value(tracker.getId());
  		writer.key("name");
  		writer.value(tracker.getName());
  	}
docs: Writes a tracker.
  
  @param writer
  used writer.
  @param tracker
  tracker to writer.
  @throws JSONException
  if error occurs.