Google Earth plugin — how to check if an element with an ID already exists?

Question

I create and assign a style the following way (C# for example):

// ge — IGEPlugin instance
var placemark1 = ge.createPlacemark("placemark1");
var style1 = ge.createStyle("style1");
style1.getLineStyle().setWidth(2);
placemark1.setStyleSelector(style1);
// ... add placemark to ge features...

How can I check if the element with the ID style1 already exists in GE ? If I call ge.createPlacemark("placemark1") , the second time I do it I get an COM error.

I can't get the element with ge.getElementById("style1") — it always returns null.

Answer 1

There are a couple of things, firstly there is an accessor getComputedStyle that will allow you to get an objects style properties as a KMLStyle object.

dynamic placemarkStyle = placemark1.getComputedStyle();
string id = placemarkStyle.getId();

Maybe you can use this method to reference the style object as you require...

You can also obtain an array of all elements of a certain type by passing the type name as a string to getElementsByType . Something like this should work (although it is untested...)

public bool DoesStyleExist(string id)
{
  var styles = ge.getElementsByType('style');
  int l = styles.getLength();

  if(l == 0) 
  {
    // no styles
    return false;
  }

  for (var i = 0; i < l; ++i) {
    var style = style.item(i);
    var styleid = style.getId();
    if(id == styleid)
    {
      // matching style id
      return true;
    }
  }

  // no match
  return false;
}

EDIT

Based on your comment you must have an error somewhere in your code - I have tested the following and it works as expected.

  // create the placemark
  placemark = ge.createPlacemark('pm1');
  var point = ge.createPoint('');
  point.setLatitude(37);
  point.setLongitude(-122);
  placemark.setGeometry(point);

  // add the placemark to the earth DOM
  ge.getFeatures().appendChild(placemark);

  var styleMap = ge.createStyleMap('');

  // Create normal style for style map
  var normalStyle = ge.createStyle('style1');
  var normalIcon = ge.createIcon('icon1');
  normalIcon.setHref('http://maps.google.com/mapfiles/kml/shapes/triangle.png');
  normalStyle.getIconStyle().setIcon(normalIcon);

  // Create highlight style for style map
  var highlightStyle = ge.createStyle('style2');
  var highlightIcon = ge.createIcon('icon2');
  highlightIcon.setHref('http://maps.google.com/mapfiles/kml/shapes/square.png');
  highlightStyle.getIconStyle().setIcon(highlightIcon);

  styleMap.setNormalStyle(normalStyle);
  styleMap.setHighlightStyle(highlightStyle);

  // Apply stylemap to a placemark
  placemark.setStyleSelector(styleMap);

  alert(ge.getElementById('pm1')); // object 
  alert(ge.getElementById('style1')); // object 
  alert(ge.getElementById('style2')); // object

  DoesStyleExist('style1'); // true
  DoesStyleExist('style2'); // true
  DoesStyleExist('foo'); // false