package com.gis{    import com.esri.ags.SpatialReference;    import com.esri.ags.geometry.MapPoint;    import com.esri.ags.geometry.Polygon;    public class Circle extends Polygon    {        private var pointNum:int = 100;        /**          * @param center               圆心         * @param radius               半径         * @param spatialReference     空间参考         *          */             public function Circle(center:MapPoint, radius:Number, spatialReference:SpatialReference=null)        {
                 super(null, spatialReference);            this.addRing(getPoints(center, radius));        }        private function getPoints(center:MapPoint, radius:Number):Array        {
                 var x:Number;            var y:Number;            var points:Array=[];            var angle:Number;            for (var i:int=0; i < this.pointNum; i++)            {                angle = Math.PI * 2 * i / this.pointNum;                x=center.x + radius * Math.sin(angle);                y=center.y + radius * Math.cos(angle);                points.push(new MapPoint(x, y));            }            return points;        }    }}