ArcGIS API for Silverlight 解决众多密集点分层显示
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问题提出：
在实际中通常会遇到这样的情况，如果地图范围小，而且需要在地图上展示的元素又比较多的时候（在展现元素符号的同时，还展示元素名称或其他属性值等），这样如果在首次加载地图的时候一次性全部显示，必然会出现严重的重叠现象，怎么解决？
解决思路：
我想大家首先想到的就是分层显示，不错，其实这就是一个方便可行的思路。为数据库表中增加一个显示层次的字段，比如叫ShowLevel，默认是0-第一层显示，1-第二层显示...,然后在Map的Layers中添加多个Graphics，有几层就设置多少个，然后在后台程序中通过判断元素是ShowLevel属性，将元素添加到各自不同的Graphics当中去，最后处理Map的ExtendChanged事件，找到一个显示的边界值，然后通过判断当前的缩放比例是否达到了这个边界值，如果达到了，就显示第二层，如果没有达到就隐藏。
具体实现及部分代码如下：
1、首先数据库中增加一个字段，ShowLevel，默认值为0
2、在MainPage.xaml中多增加几个Graphics
<esri:Map.Layers> <esri:GraphicsLayer ID="MyGraphicsLayer"> </esri:GraphicsLayer> <esri:GraphicsLayer ID="MyGraphicsLayer3"> </esri:GraphicsLayer> <!--站点名称--> <esri:GraphicsLayer ID="GraphicsLayer1"> </esri:GraphicsLayer> <esri:GraphicsLayer ID="GraphicsLayer11"> </esri:GraphicsLayer> <!--站点数据--> <esri:GraphicsLayer ID="GraphicsLayer2"> </esri:GraphicsLayer> <esri:GraphicsLayer ID="GraphicsLayer22"> </esri:GraphicsLayer> <!--站点编码--> <esri:GraphicsLayer ID="GraphicsLayer3"> </esri:GraphicsLayer> <esri:GraphicsLayer ID="GraphicsLayer33"> </esri:Map.Layers>
3、MainPage.xaml.cs中根据ShowLevel字段值，分别添加到各自的Graphics中
ESRI.ArcGIS.Client.Projection.WebMercator mercator = new ESRI.ArcGIS.Client.Projection.WebMercator(); //每次加载时先清空地图上数据 GraphicsLayer graphicsLayer = myMap.Layers["MyGraphicsLayer"] as GraphicsLayer; graphicsLayer.ClearGraphics(); GraphicsLayer graphicsLayer0 = myMap.Layers["MyGraphicsLayer3"] as GraphicsLayer; graphicsLayer0.ClearGraphics(); GraphicsLayer graphicsLayer1 = myMap.Layers["GraphicsLayer1"] as GraphicsLayer; graphicsLayer1.ClearGraphics(); GraphicsLayer graphicsLayer2 = myMap.Layers["GraphicsLayer2"] as GraphicsLayer; graphicsLayer2.ClearGraphics(); GraphicsLayer graphicsLayer3 = myMap.Layers["GraphicsLayer3"] as GraphicsLayer; graphicsLayer3.ClearGraphics(); GraphicsLayer graphicsLayer11 = myMap.Layers["GraphicsLayer11"] as GraphicsLayer; graphicsLayer11.ClearGraphics(); GraphicsLayer graphicsLayer22 = myMap.Layers["GraphicsLayer22"] as GraphicsLayer; graphicsLayer22.ClearGraphics(); GraphicsLayer graphicsLayer33 = myMap.Layers["GraphicsLayer33"] as GraphicsLayer; graphicsLayer33.ClearGraphics(); //获取到所有的山洪雨量点 ObservableCollection<RainFall> lists = e.Result; //从集合中找出最大值对应的经纬度坐标 RainFall max = lists.OrderByDescending(s => s.YL24).FirstOrDefault(); //动态添加点到地图上 Graphic graphic = null; //第一层 Graphic graphic2 = null; //第二层 foreach (RainFall item in lists) { if (!string.IsNullOrEmpty(item.Latitute.ToString()) && !string.IsNullOrEmpty(item.Longitute.ToString())) { //有坐标值时，将该监测点添加到地图上去 if (max.YLZBM == item.YLZBM) { if (max.YL24 != 0) { //最大值不为0,红点闪烁 graphic = new Graphic() { Geometry = mercator.FromGeographic(new MapPoint(double.Parse(item.Latitute.ToString().Trim()), double.Parse(item.Longitute.ToString().Trim()))), Symbol = LayoutRoot.Resources["DefaultMarkerSymbol"] as Symbol }; } else { //保持原来的蓝色标记点符号 graphic = new Graphic() { Geometry = mercator.FromGeographic(new MapPoint(double.Parse(item.Latitute.ToString().Trim()), double.Parse(item.Longitute.ToString().Trim()))), Symbol = LayoutRoot.Resources["BlueMarkerSymbol"] as Symbol }; } //保存属性 graphic.Attributes["YLZBM"] = item.YLZBM; //雨量站编码 graphic.Attributes["YLZMC"] = item.ZDMC; //雨量站名称 graphic.Attributes["YL24"] = item.YL24; //２４小时雨量 graphic.Attributes["DTNow"] = item.DTNow; //当前时间 graphic.Attributes["Latitute"] = item.Latitute; //纬度 graphic.Attributes["Longitute"] = item.Longitute; //经度 //将该Graphics添加到GraphicsLayer中去 graphicsLayer.Graphics.Add(graphic); graphicsLayer.Opacity = 1; //鼠标移入事件 graphic.MouseEnter += new MouseEventHandler(sh_graphic_MouseEnter); graphic.MouseLeave += new MouseEventHandler(sh_graphic_MouseLeave); //鼠标点击事件 #region 站点名称 //动态添加文本 TextSymbol textSymbol = new TextSymbol() { FontFamily = new System.Windows.Media.FontFamily("Microsoft YaHei"), Foreground = new System.Windows.Media.SolidColorBrush(Color.FromArgb(255, 117, 20, 99)), FontSize = 12, Text = item.ZDMC, OffsetX = 12, OffsetY = -5 }; Graphic graphicText1 = new Graphic() { Geometry = mercator.FromGeographic(new MapPoint(double.Parse(item.Latitute.ToString().Trim(), System.Globalization.CultureInfo.InvariantCulture), double.Parse(item.Longitute.ToString().Trim(), System.Globalization.CultureInfo.InvariantCulture))), Symbol = textSymbol }; graphicText1.Attributes["TextYLZMC"] = item.ZDMC; graphicsLayer1.Graphics.Add(graphicText1); #endregion #region 水位/雨量 数值 if (item.YL24 != 0) { TextSymbol textSymbol2 = new TextSymbol() { FontFamily = new System.Windows.Media.FontFamily("Microsoft YaHei"), Foreground = new System.Windows.Media.SolidColorBrush(Color.FromArgb(255, 255, 0, 0)), FontSize = 14, Text = item.YL24.ToString(), OffsetX = 10, OffsetY = 23 }; Graphic graphicText2 = new Graphic() { Geometry = mercator.FromGeographic(new MapPoint(double.Parse(item.Latitute.ToString().Trim(), System.Globalization.CultureInfo.InvariantCulture), double.Parse(item.Longitute.ToString().Trim(), System.Globalization.CultureInfo.InvariantCulture))), Symbol = textSymbol2 }; graphicText2.Attributes["TextYL"] = item.YL24; graphicsLayer2.Graphics.Add(graphicText2); } #endregion #region 站点编码 //动态添加站点编码 TextSymbol textSymbol3 = new TextSymbol() { FontFamily = new System.Windows.Media.FontFamily("Microsoft YaHei"), Foreground = new System.Windows.Media.SolidColorBrush(Color.FromArgb(255, 0, 0, 0)), FontSize = 12, Text = item.YLZBM, OffsetX = 27, OffsetY = 23 }; Graphic graphicText3 = new Graphic() { Geometry = mercator.FromGeographic(new MapPoint(double.Parse(item.Latitute.ToString().Trim(), System.Globalization.CultureInfo.InvariantCulture), double.Parse(item.Longitute.ToString().Trim(), System.Globalization.CultureInfo.InvariantCulture))), Symbol = textSymbol3 }; graphicText3.Attributes["TextYLZBM"] = item.YLZBM; graphicsLayer3.Graphics.Add(graphicText3); graphicsLayer3.Visible = false; #endregion //左键点击事件 graphic.MouseLeftButtonDown += new MouseButtonEventHandler(sh_graphic_MouseLeftButtonDown); graphic.MouseLeftButtonUp += new MouseButtonEventHandler(sh_graphic_MouseLeftButtonUp); } else { //这里判断显示层数 if (item.ShowLevel == 0) { #region 显示第一层数据 graphic = new Graphic() { Geometry = mercator.FromGeographic(new MapPoint(double.Parse(item.Latitute.ToString().Trim()), double.Parse(item.Longitute.ToString().Trim()))), Symbol = LayoutRoot.Resources["BlueMarkerSymbol"] as Symbol }; //保存属性 graphic.Attributes["YLZBM"] = item.YLZBM; //雨量站编码 graphic.Attributes["YLZMC"] = item.ZDMC; //雨量站名称 graphic.Attributes["YL24"] = item.YL24; //２４小时雨量 graphic.Attributes["DTNow"] = item.DTNow; //当前时间 graphic.Attributes["Latitute"] = item.Latitute; //纬度 graphic.Attributes["Longitute"] = item.Longitute; //经度 //将该Graphics添加到GraphicsLayer中去 graphicsLayer.Graphics.Add(graphic); graphicsLayer.Opacity = 1; //鼠标移入事件 graphic.MouseEnter += new MouseEventHandler(sh_graphic_MouseEnter); graphic.MouseLeave += new MouseEventHandler(sh_graphic_MouseLeave); //鼠标点击事件 #region 站点名称 //动态添加文本 TextSymbol textSymbol = new TextSymbol() { FontFamily = new System.Windows.Media.FontFamily("Microsoft YaHei"), Foreground = new System.Windows.Media.SolidColorBrush(Color.FromArgb(255, 117, 20, 99)), FontSize = 12, Text = item.ZDMC, OffsetX = 12, OffsetY = -5 }; Graphic graphicText1 = new Graphic() { Geometry = mercator.FromGeographic(new MapPoint(double.Parse(item.Latitute.ToString().Trim(), System.Globalization.CultureInfo.InvariantCulture), double.Parse(item.Longitute.ToString().Trim(), System.Globalization.CultureInfo.InvariantCulture))), Symbol = textSymbol }; graphicText1.Attributes["TextYLZMC"] = item.ZDMC; graphicsLayer1.Graphics.Add(graphicText1); #endregion #region 水位/雨量 数值 if (item.YL24 != 0) { TextSymbol textSymbol2 = new TextSymbol() { FontFamily = new System.Windows.Media.FontFamily("Microsoft YaHei"), Foreground = new System.Windows.Media.SolidColorBrush(Color.FromArgb(255, 255, 0, 0)), FontSize = 14, Text = item.YL24.ToString(), OffsetX = 10, OffsetY = 23 }; Graphic graphicText2 = new Graphic() { Geometry = mercator.FromGeographic(new MapPoint(double.Parse(item.Latitute.ToString().Trim(), System.Globalization.CultureInfo.InvariantCulture), double.Parse(item.Longitute.ToString().Trim(), System.Globalization.CultureInfo.InvariantCulture))), Symbol = textSymbol2 }; graphicText2.Attributes["TextYL"] = item.YL24; graphicsLayer2.Graphics.Add(graphicText2); } #endregion #region 站点编码 //动态添加站点编码 TextSymbol textSymbol3 = new TextSymbol() { FontFamily = new System.Windows.Media.FontFamily("Microsoft YaHei"), Foreground = new System.Windows.Media.SolidColorBrush(Color.FromArgb(255, 0, 0, 0)), FontSize = 12, Text = item.YLZBM, OffsetX = 27, OffsetY = 23 }; Graphic graphicText3 = new Graphic() { Geometry = mercator.FromGeographic(new MapPoint(double.Parse(item.Latitute.ToString().Trim(), System.Globalization.CultureInfo.InvariantCulture), double.Parse(item.Longitute.ToString().Trim(), System.Globalization.CultureInfo.InvariantCulture))), Symbol = textSymbol3 }; graphicText3.Attributes["TextYLZBM"] = item.YLZBM; graphicsLayer3.Graphics.Add(graphicText3); graphicsLayer3.Visible = false; #endregion //左键点击事件 graphic.MouseLeftButtonDown += new MouseButtonEventHandler(sh_graphic_MouseLeftButtonDown); graphic.MouseLeftButtonUp += new MouseButtonEventHandler(sh_graphic_MouseLeftButtonUp); #endregion } else { #region 显示第二层数据 graphic2 = new Graphic() { Geometry = mercator.FromGeographic(new MapPoint(double.Parse(item.Latitute.ToString().Trim()), double.Parse(item.Longitute.ToString().Trim()))), Symbol = LayoutRoot.Resources["BlueMarkerSymbol"] as Symbol }; //保存属性 graphic2.Attributes["YLZBM"] = item.YLZBM; //雨量站编码 graphic2.Attributes["YLZMC"] = item.ZDMC; //雨量站名称 graphic2.Attributes["YL24"] = item.YL24; //２４小时雨量 graphic2.Attributes["DTNow"] = item.DTNow; //当前时间 graphic2.Attributes["Latitute"] = item.Latitute; //纬度 graphic2.Attributes["Longitute"] = item.Longitute; //经度 //将该Graphics添加到GraphicsLayer中去 graphicsLayer0.Graphics.Add(graphic2); graphicsLayer0.Opacity = 1; if (currentValue > tip_Base.sideValue) { graphicsLayer0.Visible = false; } else { graphicsLayer0.Visible = true; } //鼠标移入事件 graphic2.MouseEnter += new MouseEventHandler(sh_graphic_MouseEnter); graphic2.MouseLeave += new MouseEventHandler(sh_graphic_MouseLeave); //鼠标点击事件 #region 站点名称 //动态添加文本 TextSymbol textSymbol = new TextSymbol() { FontFamily = new System.Windows.Media.FontFamily("Microsoft YaHei"), Foreground = new System.Windows.Media.SolidColorBrush(Color.FromArgb(255, 117, 20, 99)), FontSize = 12, Text = item.ZDMC, OffsetX = 12, OffsetY = -5 }; Graphic graphicText1 = new Graphic() { Geometry = mercator.FromGeographic(new MapPoint(double.Parse(item.Latitute.ToString().Trim(), System.Globalization.CultureInfo.InvariantCulture), double.Parse(item.Longitute.ToString().Trim(), System.Globalization.CultureInfo.InvariantCulture))), Symbol = textSymbol }; graphicText1.Attributes["TextYLZMC"] = item.ZDMC; graphicsLayer11.Graphics.Add(graphicText1); if (currentValue > tip_Base.sideValue) { graphicsLayer11.Visible = false; } else { graphicsLayer11.Visible = true; } #endregion #region 水位/雨量 数值 if (item.YL24 != 0) { TextSymbol textSymbol2 = new TextSymbol() { FontFamily = new System.Windows.Media.FontFamily("Microsoft YaHei"), Foreground = new System.Windows.Media.SolidColorBrush(Color.FromArgb(255, 255, 0, 0)), FontSize = 14, Text = item.YL24.ToString(), OffsetX = 10, OffsetY = 23 }; Graphic graphicText2 = new Graphic() { Geometry = mercator.FromGeographic(new MapPoint(double.Parse(item.Latitute.ToString().Trim(), System.Globalization.CultureInfo.InvariantCulture), double.Parse(item.Longitute.ToString().Trim(), System.Globalization.CultureInfo.InvariantCulture))), Symbol = textSymbol2 }; graphicText2.Attributes["TextYL"] = item.YL24; graphicsLayer22.Graphics.Add(graphicText2); if (currentValue > tip_Base.sideValue) { graphicsLayer22.Visible = false; } else { graphicsLayer22.Visible = true; } } #endregion #region 站点编码 //动态添加站点编码 TextSymbol textSymbol3 = new TextSymbol() { FontFamily = new System.Windows.Media.FontFamily("Microsoft YaHei"), Foreground = new System.Windows.Media.SolidColorBrush(Color.FromArgb(255, 0, 0, 0)), FontSize = 12, Text = item.YLZBM, OffsetX = 27, OffsetY = 23 }; Graphic graphicText3 = new Graphic() { Geometry = mercator.FromGeographic(new MapPoint(double.Parse(item.Latitute.ToString().Trim(), System.Globalization.CultureInfo.InvariantCulture), double.Parse(item.Longitute.ToString().Trim(), System.Globalization.CultureInfo.InvariantCulture))), Symbol = textSymbol3 }; graphicText3.Attributes["TextYLZBM"] = item.YLZBM; graphicsLayer33.Graphics.Add(graphicText3); graphicsLayer33.Visible = false; #endregion //左键点击事件 graphic2.MouseLeftButtonDown += new MouseButtonEventHandler(sh_graphic_MouseLeftButtonDown); graphic2.MouseLeftButtonUp += new MouseButtonEventHandler(sh_graphic_MouseLeftButtonUp); #endregion } } } else { //不做任何处理，不添加任何点信息 } }4、在Map的ExtendChanged事件中处理
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