ArcGIS图层和要素的过滤显示
ArcGIS可以设置动态地图服务（ArcGISDynamicMapServiceLayer）显示哪些图层，也可以设置每个图层根据某个属性字段的某些条件来进行过滤显示。
1、设置显示的图层
主要是通过ArcGISDynamicMapServiceLayer的VisibleLayers属性来设置或得到当前显示的图层，C#代码如下：
代码中Map1和TextBlock_VisibleLayers是已经定义好的地图和TextBlock控件。
//ArcGISDynamicMapServiceLayer初始化函数 private void ArcGISDynamicMapServiceLayer_Initialized(object sender, System.EventArgs e) { //得到ArcGISDynamicMapServiceLayer，这里是第一个图层，根据实际情况，可以通过Map.Layers["图层的ID"]来得到 ArcGISDynamicMapServiceLayer myArcGISDynamicMapServiceLayer = (ArcGISDynamicMapServiceLayer)Map1.Layers[0]; //VisibleLayers的读写 //下面注释的代码：设置myArcGISDynamicMapServiceLayer第二和第三个图层显示 //int[] myVisibleLayers2 = { 1, 2 }; //myArcGISDynamicMapServiceLayer.VisibleLayers = myVisibleLayers2; //得到显示的图层ID int[] myVisibleLayers = myArcGISDynamicMapServiceLayer.VisibleLayers; if (myVisibleLayers != null) { string myVisibleLayersText = "Number VisibleLayers: " + myVisibleLayers.Length.ToString(); string myVisibleLayersText2 = ""; int i = 0; for (i = 0; i < myVisibleLayers.Length; ++i) { myVisibleLayersText2 = myVisibleLayersText2 + " " + myVisibleLayers[i].ToString(); } TextBlock_VisibleLayers.Text = myVisibleLayersText + ". VisibleLayers ID's: " + myVisibleLayersText2; } else { TextBlock_VisibleLayers.Text = "[VisibleLayers not set - Meaning all layers are visible.]"; } }
2、设置图层根据字段条件过滤显示
如果不全部显示一个图层的所有要素，而是根据某些条件来“过滤显示”，则可以通过设置LayerDefinition来实现。
LayerDefinition的设置可以通过XAML代码实现：
<StackPanel Name="StackPanel1" Height="400" Width="400" Margin="0,0,0,0" HorizontalAlignment="Left" VerticalAlignment="Top" > <esri:Map Background="White" Name="Map1" Height="200" Width="400"> <!-- Set the LayerDefinition for the ArcGISDynamicMapServiceLayer. --> <!-- By default no LayerDefinition is set unless explicitly set on the server. --> <esri:ArcGISDynamicMapServiceLayer Url="http://sampleserver3.arcgisonline.com/ArcGIS/rest/services/Earthquakes/Since_1970/MapServer" /> <esri:ArcGISDynamicMapServiceLayer.LayerDefinitions> <!-- LayerID="0" is the Earthquakes1970 layer. The Definition only displays earth quakes that have a Magnitude greater than 6. The field Magnitude is of type esriFieldTypeDouble. --> <esri:LayerDefinition LayerID="0" Definition="Magnitude > 6" /> <!-- LayerID="0" is the Earthquakes1970 layer. The Definition only displays earth quakes that have a Magnitude greater than 3 and less than 6. The field Magnitude is of type esriFieldTypeDouble. --> <!-- <esri:LayerDefinition LayerID="0" Definition="Magnitude > 3 AND Magnitude < 6" /> --> <!-- Another example where the Name of the earth quake event is to contains the letters 'CHINA'. Note: the Definition is case sensitive. The field Name is of type esriFieldTypeString. --> <!-- <esri:LayerDefinition LayerID="0" Definition="Name LIKE 'CHINA'" /> --> <!-- Another example where the Name of the earth quake event is exactly matches the letters 'VENEZUELA'. Note: the Definition is case sensitive. The field Name is of type esriFieldTypeString. --> <!-- <esri:LayerDefinition LayerID="0" Definition="Name = 'VENEZUELA'" /> --> <!-- Another example where the earth quake events are displayed if they occured after January 15, 2000. The field Date_ is of type esriFieldTypeDate. --> <!-- <esri:LayerDefinition LayerID="0" Definition="Date_ > DATE '1/15/2000'" />--> </esri:ArcGISDynamicMapServiceLayer.LayerDefinitions> </esri:ArcGISDynamicMapServiceLayer> </esri:Map> <!-- LayerDefinitions Property (Read) --> <TextBlock Height="23" Name="TextBlock_LayerDefinitions" Text="{Binding ElementName=Map1, Path=Layers[0].LayerDefinitions[0].Definition}" /> </StackPanel>
也可以通过代码来实现，C#代码如下：
//ArcGISDynamicMapServiceLayer初始化函数 private void ArcGISDynamicMapServiceLayer_Initialized(object sender, System.EventArgs e) { //得到ArcGISDynamicMapServiceLayer，这里是第一个图层，根据实际情况，可以通过Map.Layers["图层的ID"]来得到 ArcGISDynamicMapServiceLayer myArcGISDynamicMapServiceLayer = (ArcGISDynamicMapServiceLayer)Map1.Layers[0]; //LayerDefinition的读写 //设置图层的LayerDefinition，默认情况下LayerDefinition是没有设置的 //得到图层的LayerDefinition ESRI.ArcGIS.Client.LayerDefinition myDefinition = new ESRI.ArcGIS.Client.LayerDefinition(); myDefinition.LayerID = 0; //设置LayerDefinition，属性字段“Magnitude”属于ID为0的图层 //LayerDefinition的设置语句和Query中的Where语句一样 //字段Magnitude的类型是esriFieldTypeDouble. myDefinition.Definition = "Magnitude > 6"; // The Definition only displays earth quakes that have a Magnitude greater than 3 and less that 6. // The field Magnitude is of type esriFieldTypeDouble. // myDefinition.Definition = "Magnitude > 3 AND Magnitude < 6"; // Another example where the Name of the earth quake event is to contains the letters 'CHINA'. // Note: the Definition is case sensitive. The field Name is of type esriFieldTypeString. //myDefinition.Definition = "Name LIKE 'CHINA'"; // Another example where the Name of the earth quake event is exactly matches the letters 'VENEZUELA'. // Note: the Definition is case sensitive. The field Name is of type esriFieldTypeString. //myDefinition.Definition = "Name = 'VENEZUELA'"; // Another example where the earth quake events are displayed if they occured after January 15, 2000. // The field Date_ is of type esriFieldTypeDate. //myDefinition.Definition = "Date_ > DATE '1/15/2000'"; //创建一个ObservableCollection，add设置的LayerDefinition System.Collections.ObjectModel.ObservableCollection<LayerDefinition> myObservableCollection2 = new System.Collections.ObjectModel.ObservableCollection<LayerDefinition>(); myObservableCollection2.Add(myDefinition); //启动设置的LayerDefinition myArcGISDynamicMapServiceLayer.LayerDefinitions = myObservableCollection2; //得到已经存在的LayerDefinitions collection. System.Collections.ObjectModel.ObservableCollection<LayerDefinition> myObservableCollection = myArcGISDynamicMapServiceLayer.LayerDefinitions; if (myObservableCollection.Count > 0) { //得到第一个LayerDefinition ESRI.ArcGIS.Client.LayerDefinition myLayerDefinition = myObservableCollection[0]; //得到LayerDefinition的信息 TextBlock_LayerDefinitions.Text = "For Layer: " + myLayerDefinition.LayerID.ToString() + ". The Defintion is: " + myLayerDefinition.Definition; } else { TextBlock_LayerDefinitions.Text = "[NO LayerDefinitions SET]"; } }
上面ArcGISDynamicMapServiceLayer_Initialized(object sender, System.EventArgs e)函数是订阅到ArcGISDynamicMapServiceLayer.Initialized的，也就是在图层加载的时候就设置了“过滤”条件，如果要在后期在某个响应事件中动态的刷新地图，需要在设置LayerDefinition后，调用ArcGISDynamicMapServiceLayer.Refresh()函数来刷新地图才能看到效果。
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