ArcGis For Silverlight API,地图显示Gis,绘制点，线，绘制图等(四)--动态绘制点

<!--与用户交互的GraphicsLayer-->
            <esri:GraphicsLayer ID="GLayer">
            </esri:GraphicsLayer>
            <esri:GraphicsLayer ID="WDLayer">
            </esri:GraphicsLayer>

List<Graphic> mapPoint = new List<Graphic>(); // 绘制站点的图形
        List<Graphic> WDPic = new List<Graphic>();    // 绘制风符号图片

/// <sumMary>
        /// 海浪一号报文
        /// </sumMary>
        private void WaveIInit()
        {
            GetWaveservice.WaveserviceSoapClient porxy = new MapSilverlight.GetWaveservice.WaveserviceSoapClient();
            porxy.GetSeaInfoCompleted += new EventHandler<MapSilverlight.GetWaveservice.GetSeaInfoCompletedEventArgs>(porxy_GetSeaInfoCompleted);
            porxy.GetSeaInfoAsync();
        }
        /// <sumMary>
        /// 异步接收完海浪一号报文后即绘制图形到地图上
        /// </sumMary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        void porxy_GetSeaInfoCompleted(object sender,MapSilverlight.GetWaveservice.GetSeaInfoCompletedEventArgs E)
        {
            // 获取数据长度
            int length = e.Result.Count;

            // 绘制站点层
            GraphicsLayer glayer = new GraphicsLayer();
            glayer = mymap.Layers["GLayer"] as GraphicsLayer;

            // 绘制风向层
            GraphicsLayer WDLayer = new GraphicsLayer();
            WDLayer = mymap.Layers["WDLayer"] as GraphicsLayer;


            // 定义一个转换类,将字符串地址转化为图片
            ImagesourceConverter converter = new ImagesourceConverter();

            // 实例化站点和风向
            mapPoint = new List<Graphic>();
            WDPic = new List<Graphic>();

            // 循环从结果集中取数据
            for (int i = 0; i < length; i++)
            {
                waveI.Add(new WebModel.Sites(e.result[i].Longitude,e.result[i].Latitude,e.result[i].SiteNo,e.result[i].Pressure,e.result[i].RH,e.result[i].Temperature,e.result[i].Visibility));

                // 将站点添加到站点层
                mapPoint.Add(new Graphic()
                {
                    Geometry = new MapPoint(Convert.ToDouble(e.result[i].LongitudE),Convert.ToDouble(e.result[i].LatitudE)),Symbol = new SimpleMarkerSymbol()
                    {
                        Color = new SolidColorBrush(Colors.Red),Size = 6,Style = SimpleMarkerSymbol.SimpleMarkerStyle.Circle
                    }
                });

                // 将风向添加到风向层
                WDPic.Add(new Graphic()
                {
                    Geometry = new MapPoint(Convert.ToDouble(e.result[i].LongitudE),Symbol = new PictuREMARKerSymbol() 
                    {
                        source = (ImagesourcE)converter.ConvertFromString("wind/1.png")
                    }
                });
            }

            // 调用动态绘图方法绘制站点
            DynamicDrawSymbol(glayer,mapPoint,mymap);
            // 调用动态绘图方法绘制风向
            DynamicDrawSymbol(WDLayer,WDPic,mymap);
        }

GraphicsLayer glayer = new GraphicsLayer();
            glayer = mymap.Layers["GLayer"] as GraphicsLayer;

            GraphicsLayer WDLayer = new GraphicsLayer();
            WDLayer = mymap.Layers["WDLayer"] as GraphicsLayer;

            // 调用动态绘图方法绘制站点
            DynamicDrawSymbol(glayer,mymap);

            
            // 调用动态绘图方法绘制风向
            if (mymap.Extent.Height < 10)
            {
                WDLayer.Visible = true;
                DynamicDrawSymbol(WDLayer,mymap);
            }
            else
            {
                WDLayer.Visible = false;
            }

/// <sumMary>
        /// 动态的绘制图层
        /// 当然地图移动到相应的坐标后绘制(保留原来的点,绘制新的数据)
        /// 实现了无刷新绘制
        /// </sumMary>
        /// <param name="glayer">表示地图上的层</param>
        /// <param name="cacheGraphic">存放 Graphics 的缓存</param>
        /// <param name="map">表示一张 ArcGis 地图</param>
        private void DynamicDrawSymbol(ESRI.ArcGIs.CLIENt.GraphicsLayer glayer,List<ESRI.ArcGIs.CLIENt.Graphic> cacheGraphic,ESRI.ArcGIs.CLIENt.Map map)
        {
            // 以下四个变量分别表示地图的四个边
            // 即最大经纬度和最小经纬度
            // xMax最大经度,ymax最大纬度
            double xMax = map.Extent.XMax;
            double xMin = map.Extent.XMin;
            double ymax = map.Extent.ymax;
            double ymin = map.Extent.ymin;

            // 去除不在坐标范围内的点,先检查图层是否为空
            if (glayer != null)
            {
                int graphicCount = glayer.Graphics.Count;
                for (int i = 0; i < graphicCount; i++)
                {
                    // 判断经度,纬度
                    if (!((glayer.Graphics[i].Geometry.Extent.XMax < xMax && glayer.Graphics[i].Geometry.Extent.XMax > xMin)
                        && (glayer.Graphics[i].Geometry.Extent.ymax < ymax && glayer.Graphics[i].Geometry.Extent.ymax > ymin)))
                    {
                        // 将点在地图上移除,并放在缓存中
                        cacheGraphic.Add(glayer.Graphics[i]);
                        glayer.Graphics.Remove(glayer.Graphics[i]);
                        graphicCount--;   // 当从集合中移除元素时应该把 graphicCount 减1
                        i--;              // 元素被移除后相当于当前元素的后一位元素会 -1,应该再循环一次本次循环所以应该 -1
                    }
                } // i
            }

            // 检查缓存是否为空,并将点绘制到图形上
            if (cacheGraphic != null)
            {
                int count = cacheGraphic.Count;
                for (int i = 0; i < count; i++)
                {
                    // 判断经度,纬度
                    if ((cacheGraphic[i].Geometry.Extent.XMax < mymap.Extent.XMax && cacheGraphic[i].Geometry.Extent.XMax > mymap.Extent.XMin)
                        && (cacheGraphic[i].Geometry.Extent.ymax < mymap.Extent.ymax && cacheGraphic[i].Geometry.Extent.ymax > mymap.Extent.ymin))
                    {
                        // 运行到此则该点在目前地图范围内,将该点加入到地图中
                        glayer.Graphics.Add(cacheGraphic[i]);
                        cacheGraphic.Remove(cacheGraphic[i]);
                        count--;    // 当从集合中移除元素时应该把 count 减1
                        i--;        // 元素被移除后相当于当前元素的后一位元素会 -1,应该再循环一次本次循环所以应该 -1
                        conTinue;
                    }
                }
            }
        }