void ReadMainlineObjectRef(XmlElement element, SpriterMainlineKey key)
{
var obj = new SpriterMainlineObjectRef();
key.objects.Add(obj);
foreach(XmlAttribute attribute in element.Attributes)
{
// id
if (attribute.Name.Equals("id"))
obj.ID = int.Parse(attribute.Value);
// parent
else if (attribute.Name.Equals("parent"))
obj.parent = int.Parse(attribute.Value);
// timeline
else if (attribute.Name.Equals("timeline"))
obj.timeline = int.Parse(attribute.Value);
// key
else if (attribute.Name.Equals("key"))
obj.key = int.Parse(attribute.Value);
// z_index
else if (attribute.Name.Equals("z_index"))
obj.zIndex = int.Parse(attribute.Value);
}
}