【转】ArcGIS API for Silverlight/WPF 2.1学习笔记（二）

五、Graphics layer

1、新增Graphics layer

Graphics layer用于显示用户自定义绘制的点、线、面图形。使用时确保xaml文件中Graphics layer定义在其它图层的下面，以确保它能显示在其它图层的上面。

<esri:Map x:Name="MyMap" Extent=", , , " >

<esri:Map.Layers>

<esri:ArcGISTiledMapServiceLayerID="."Url="http://../rest/./MapServer"/>

<esri:GraphicsLayer ID=”.” />

</esri:Map.Layers>

</esri:Map>

2、管理Graphics features

在Graphics layer上创建Graphics的步骤一般如下：

（1）获取Graphics layer

（2）创建或获取Graphic

（3）设置Graphic的Geometry

（4）应用Graphic的Symbol

（5）将Graphic添加到Graphics layers

代码如下：

GraphicsLayer graphicsLayer = MyMap.Layers["MyGraphicsLayer"] as GraphicsLayer;

foreach (Graphic graphic in graphicsList)

{

graphic.Symbol = MySymbol;

graphicsLayer.Graphics.Add(graphic);

}

3、使用Draw surface

Draw surface用于获取Geometries，Geometries可添加到Graphics Layer或用作identify和buffer操作。

使用Draw surface，你必须

（1）设置绘图操作的Symbols

（2）设置Draw surface的地图

（3）执行逻辑以激活|解除surface

（4）处理Geometries，以在surface上绘图

示例代码如下：

xaml文件：

<Grid x:Name="LayoutRoot" Background="White">

<Grid.Resources>

<esriSymbols:SimpleFillSymbol x:Name="RedFillSymbol" Fill="#66FF0000" BorderBrush="Red" BorderThickness="2" />

</Grid.Resources>

<esri:Map …>

…

cs文件：

MyDrawObject = new Draw(MyMap)

{ LineSymbol =LayoutRoot.Resources["DrawLineSymbol"] as LineSymbol,

FillSymbol =LayoutRoot.Resources["DrawFillSymbol"] as FillSymbol };

MyDrawObject.DrawComplete += MyDrawObject_DrawComplete;

MyDrawObject.DrawMode = DrawMode.Polygon;

MyDrawObject.IsEnabled = true;

private void MyDrawObject_DrawComplete(object sender, ESRI.ArcGIS.Client.DrawEventArgs args)

{

Graphic graphic = new Graphic() { Geometry = args.Geometry, Symbol = RedFillSymbol };

GraphicsLayer graphicsLayer = MyMap.Layers["MyGraphicsLayer"] as GraphicsLayer;

graphicsLayer.Graphics.Add(graphic);

}

4、Symbols和Renderers

Symbols定义了Graphic的非几何学方面的显示特性，如颜色、边框宽度、透明度等。

Renderers定义了一个或多个应用于Graphics layer的Symbols，指定哪些Graphics属性与哪个Symbol相符。

Symbols和Geometries类型：

Symbol	Geometry	描述
SimpleMarkerSymbol	Point	用简单形状来表现点
PictureMarkerSymbol	Point	用images来表现点
SimpleLineSymbol	Polyline	用预定义的风格来表现线
CartographicLineSymbol	Polyline	用定制的风格来表现线
SimpleFillSymbol	Polygon	用Silverlight Brush来填充多边形
PictureFillSymbol	Polygon	用images填充多边形

通常，视觉定义在xaml文件中，行为逻辑定义在.cs文件中，让表现层和业务逻辑层分开，使得应用程序更容易开发、维护和扩展。

Symbol的使用：

（1）添加命名空间：symbol类定义在ESRI.ArcGIS.Client.Symbols命名空间中（ESRI.ArcGIS.Client集）

xmlns:esriSymbols="clr-namespace:ESRI.ArcGIS.Client.Symbols;assembly=ESRI.ArcGIS.Client"

（2）xaml文件中定义Symbol

<Grid.Resources>

<esriSymbols:SimpleFillSymbol x:Name="MyRedFillSymbol" Fill="#66FF0000" BorderBrush="Red" BorderThickness="2" />

</Grid.Resources>

//Symbol运用于FeatureLayer

<esri:FeatureLayer ID="." Where="1=1" FeatureSymbol="{StaticResource MyRedFillSymbol}"

Url="http://./ArcGIS/rest/services/./MapServer/5" >

<esri:FeatureLayer.OutFields>

<sys:String>POP07_SQMI</sys:String>

</esri:FeatureLayer.OutFields>

</esri:FeatureLayer>

（3）cs文件中动态生成

SimpleFillSymbol fillSymbol = new SimpleFillSymbol()

{

BorderBrush = new SolidColorBrush(Color.FromArgb(0, 255, 0, 0)),

BorderThickness = 2,

Fill = new SolidColorBrush(Color.FromArgb(alphaVal, redVal, greenVal, blueVal))

};

//Symbol运用于GraphicsLayer的每一个graphic

GraphicsLayer graphicsLayer = MyMap.Layers["MyGraphicsLayer"] as GraphicsLayer;

foreach (Graphic graphic in graphicsLayer.Graphics)

graphic.Symbol = fillSymbol;

创建Unique Value Renderer：

<Grid.Resources>

<esriSymbols:SimpleFillSymbol x:Name="a" Fill=""BorderBrush=""BorderThickness="" />

<esriSymbols:SimpleFillSymbol x:Name="b" Fill=""BorderBrush=""BorderThickness="" />

<esriSymbols:SimpleFillSymbol x:Name="c" Fill=""BorderBrush=""BorderThickness="" />

<esri:UniqueValueRenderer x:Name="abcRenderer" Attribute="STATE_NAME" >

<esri:UniqueValueRenderer.Infos>

<esri:UniqueValueInfo Value="California" Symbol="{StaticResource a}" />

<esri:UniqueValueInfo Value="New York" Symbol="{StaticResource b}" />

<esri:UniqueValueInfo Value="Kansas" Symbol="{StaticResource c}" />

</esri:UniqueValueRenderer.Infos>

</esri:UniqueValueRenderer>

</Grid.Resources>

// FeatureLayer中，指定一个过滤，仅仅California、New York、Kansas被绘制

//并且将其STATE_NAME字段的值显示在layer的Graphics中

<esri:FeatureLayer ID=""

Where="(STATE_NAME='California') OR (STATE_NAME='New York') OR (STATE_NAME = 'Kansas')"

Renderer="{StaticResource abcRenderer}"

Url="http://sampleserver1.arcgisonline.com/ArcGIS/rest/services/Demographics/ESRI_Census_USA/MapServer/5" >

<esri:FeatureLayer.OutFields>

<sys:String>STATE_NAME</sys:String>

</esri:FeatureLayer.OutFields>

</esri:FeatureLayer>

创建Class Breaks Renderer：即将symbol应用于一组指定范围的graphics中。

<Grid.Resources>

<esriSymbols:SimpleFillSymbol x:Name="a" Fill="" BorderBrush=""BorderThickness="" />

<esriSymbols:SimpleFillSymbol x:Name="b" Fill="" BorderBrush=""BorderThickness="" />

<esriSymbols:SimpleFillSymbol x:Name="c" Fill="" BorderBrush=""BorderThickness="" />

<esri:ClassBreaksRenderer x:Name="abcRenderer" Attribute="POP07_SQMI" >

<esri:ClassBreaksRenderer.Classes>

<esri:ClassBreakInfo MinimumValue="0" MaximumValue="50" Symbol="{StaticResource a}" />

<esri:ClassBreakInfo MinimumValue="51" MaximumValue="125" Symbol="{StaticResource b}" />

<esri:ClassBreakInfo MinimumValue="125" MaximumValue="2000" Symbol="{StaticResource c}" />

</esri:ClassBreaksRenderer.Classes>

</esri:ClassBreaksRenderer>

</Grid.Resources>

// FeatureLayer中，将renderer和Feature layer联系起来，进行地图绘制

//并且将其POP07_SQMI字段的值显示在layer的Graphics中

<esri:FeatureLayer ID="" Where="1=1" Renderer="{StaticResource abcRenderer}"

Url="http://./ArcGIS/rest/services/./MapServer/5" >

<esri:FeatureLayer.OutFields>

<sys:String>POP07_SQMI</sys:String>

</esri:FeatureLayer.OutFields>

</esri:FeatureLayer>

5、使用Clustering（聚类分组，用于render的数量很大时）

当点很多和密集时，使用Clustering将点分组，使得在cluster distance内的多个点用一个点代替。Clustering可用于GraphicsLayer和Feature Layer。

（1）使用FlareClusterer

FlareClusterer可按如下方式添加到GraphicsLayer和FeatureLayer中：

<esri:GraphicsLayer ID="MyGraphicsLayer">

<esri:GraphicsLayer.Clusterer>

<esri:FlareClusterer />

</esri:GraphicsLayer.Clusterer>

</esri:GraphicsLayer>

效果如下图：



FlareClusterer的属性如下表：

FlareClusterer属性	描述
FlareBackground	填充的背景颜色（默认红色）
FlareForeground	边界和文字颜色（默认白色）
MaximumFlareCount	当鼠标移动到cluster时，各小点是否展开的最大数量界限 小于此值时，鼠标移上去会展开各小点；大于此值时，称为large clusters，其颜色和大小会根据点多少变化。（默认=10）
Radius	被cluster的半径，单位pixels（默认20）
Gradient	LinearGradientBrush线性渐变刷用于large clusters （默认：Default = LinearGradientBrush; MappingMode = RelativeToBoundingBox; GradientStop1: Offset = 0, Argb = 127,255,255,0, GradientStop2: Offset = 1, Argb = 127,255,0,0)

示例：修改FlareClusterer的默认属性

<Grid.Resources>

<LinearGradientBrush x:Name="aGradient" MappingMode="RelativeToBoundingBox" >

<GradientStop Color="#990011FF" Offset="0"/>

<GradientStop Color="#990055FF" Offset="0.25"/>

<GradientStop Color="#990099FF" Offset="0.5"/>

<GradientStop Color="#9900CCFF" Offset="0.75"/>

<GradientStop Color="#9900FFFF" Offset="1"/>

</LinearGradientBrush>

</Grid.Resources>

<esri:Map x:Name="MyMap">

<esri:Map.Layers>

<esri:GraphicsLayer ID="MyGraphicsLayer">

<esri:GraphicsLayer.Clusterer>

<esri:FlareClusterer FlareBackground="Yellow" FlareForeground="#99000000"

MaximumFlareCount="5" Radius="15" Gradient="{StaticResource aGradient}" />

</esri:GraphicsLayer.Clusterer>

</esri:GraphicsLayer>

</esri:Map.Layers>

</esri:Map>

（2）扩展GraphicsClusterer

为了定制cluster的外观，你可以创建一个继承自ESRI.ArcGIS.Client.GraphicsClusterer的类，并重写OnCreateGraphic()方法来定义cluster graphic。示例代码如下：

public class SumClusterer : GraphicsClusterer

{

public SumClusterer()

{

MinimumColor = Colors.Red;

MaximumColor = Colors.Yellow;

SymbolScale = 1;

base.Radius = 50;

}

public string AggregateColumn { get; set; }

public double SymbolScale { get; set; }

public Color MinimumColor { get; set; }

public Color MaximumColor { get; set; }

protected override Graphic OnCreateGraphic(GraphicCollection cluster, MapPoint point, int maxClusterCount)

{

if (cluster.Count == 1) return cluster[0];

Graphic graphic = null;

double sum = 0;

foreach (Graphic g in cluster)

{

if (g.Attributes.ContainsKey(AggregateColumn))

{try{sum += Convert.ToDouble(g.Attributes[AggregateColumn]); }}

}

double size = (sum + 450) / 30;

size = (Math.Log(sum * SymbolScale / 10) * 10 + 20);

if (size < 12) size = 12;

graphic=new Graphic(){Symbol=new ClusterSymbol() {Size = size},Geometry= point};

graphic.Attributes.Add("Count", sum);

graphic.Attributes.Add("Size", size);

graphic.Attributes.Add("Color", InterpolateColor(size - 12, 100));

return graphic;

}

private static Brush InterpolateColor(double value, double max)

{

value = (int)Math.Round(value * 255.0 / max);

if (value > 255) value = 255;

else if (value < 0) value = 0;

return new SolidColorBrush(Color.FromArgb(127, 255, (byte)value, 0));

}

}