====== Track Field Of View ====== This page describes how to track View updates to render Field-Of-Views on the Reference Map. ===== Listening ===== Tracking Views means listening for changes in the number of views, or changes in the state of an individual View. To do that, use these signals : * onViewOpened : fired when a View is opened. * onViewClosed : fired when a View is closed. * onViewStateChanged : fired when a View's state has changed. When any of these events occur, Views should be refreshed on the map. ===== Loading ===== Use the ''getFieldOfViews()'' function to get the list of Field-of-view objects for all views.


/**
 * Update views on the map.
 */
function updateViews() {
  var mapObjects = viewer.getFieldOfViews(null/*all*/);
  renderMapObjects(mapObjects);
}
// Listen to view changes
this.viewer.onViewStateChanged.add(updateViews);
this.viewer.onViewOpened.add(updateViews);
this.viewer.onViewClosed.add(updateViews);

// Start with an update.
// It may be the case that a view was already open prior to attaching our signal listener.
updateViews();

Below is an example that uses the above signals and shows you the returned MapObjects as the Views change. ===== Rendering ===== See [[mapobjects]].