网络分析与网络数据集—功能调用AO API

AO就像是一个万能的神，有了它，ArcGIS才能没有做不到，只有想不到。当你为了某一个功能抓耳挠腮，苦思冥想，废寝忘食的时候，其实解决之路就在AO开发帮助的某个角落痴痴地看着你。AO是ArcGIS产品系列的底层，ArcGIS Desktop、ArcGIS Engine、ArcGIS Server，理论上讲，Desktop里面能够实现的功能，通过ArcGIS Engine和ArcGIS Server也可以实现。

// Get the server context for the analysis layer
IServerContext serverContext = MapResourceLocal.ServerContextInfo.ServerContext;
IMap map = Utility.GetCartoIMap(MapInstance, "图层");
IGPMessages gpMessages = serverContext.CreateObject("esriGeodatabase.GPMessages") as IGPMessages;
INALayer2 routeNALayer = Utility.GetNALayer("Route", map);
INAContext routeNAContext = routeNALayer.CopyContext();
INAContextEdit routeNAContextEdit = routeNAContext as INAContextEdit;
routeNAContextEdit.Bind(routeNALayer.Context.NetworkDataset, gpMessages);

// Set route solver properties
INARouteSolver naRouteSolver = routeNAContext.Solver as INARouteSolver;
naRouteSolver.FindBestSequence = resequenceStops;
naRouteSolver.PreserveFirstStop = false;
naRouteSolver.PreserveLastStop = false;

// Remove any existing stops
IFeatureClass stopsFClass = routeNAContext.NAClasses.get_ItemByName("Stops") as IFeatureClass;
INAClass stopsNAClass = stopsFClass as INAClass;
stopsNAClass.DeleteAllRows();

// Get locator and initialize variables
INALocator2 naLocator = routeNAContext.Locator as INALocator2;
INALocation naLocation = serverContext.CreateObject("esriNetworkAnalyst.NALocation") as INALocation;
IFeature stopFeature;
INALocationObject stopNALocation;
IRowSubtypes stopFeatureRowSubtypes;
IPoint outPoint = serverContext.CreateObject("esriGeometry.Point") as IPoint;
double distanceFromPoint = 0;
int sequenceNumber = 0;
int sequenceIndex = stopsFClass.FindField("SEQUENCE");
int statusIndex = stopsFClass.FindField("STATUS");
int nameIndex = stopsFClass.FindField("NAME");

// Load the stops
ElementGraphicsLayer stopsLayer = PointsGraphicsLayer;
foreach (DataRow dr in stopsLayer.Rows)
{
sequenceNumber++;
// Get point
ESRI.ArcGIS.ADF.Web.Geometry.Point adfPoint = (ESRI.ArcGIS.ADF.Web.Geometry.Point)stopsLayer.GeometryFromRow(dr);
PointN pointN = ESRI.ArcGIS.ADF.Web.DataSources.ArcGISServer.Converter.FromAdfPoint(adfPoint);
IPoint point = ESRI.ArcGIS.ADF.ArcGISServer.Converter.ValueObjectToComObject(pointN, serverContext) as IPoint;
// Create Stop
stopFeature = stopsFClass.CreateFeature();
stopFeatureRowSubtypes = stopFeature as IRowSubtypes;
stopNALocation = stopFeature as INALocationObject;
stopFeatureRowSubtypes.InitDefaultValues();
// Get Location
naLocator.QueryLocationByPoint(point, ref naLocation, ref outPoint, ref distanceFromPoint);
// Set Stop properties
stopFeature.Shape = point;
stopFeature.set_Value(sequenceIndex, sequenceNumber);
stopFeature.set_Value(nameIndex, string.Format("{0}, {1}", Math.Round(adfPoint.X, 4), Math.Round(adfPoint.Y, 4)));
if (naLocation.IsLocated)
{
stopNALocation.NALocation = naLocation;
stopFeature.set_Value(statusIndex, esriNAObjectStatus.esriNAObjectStatusOK);
}
else
{
stopFeature.set_Value(statusIndex, esriNAObjectStatus.esriNAObjectStatusNotLocated);
}
// Store the Stop
stopFeature.Store();
}

// Message all of the network analysis agents that the analysis context has changed
routeNAContextEdit.ContextChanged();
gpMessages.Clear();
INASolver naSolver = routeNAContext.Solver;

//Solve route
bool partialResults = naSolver.Solve(routeNAContext, gpMessages, null);

// report errors
if (partialResults || gpMessages.Count > 0)
{
StringBuilder sErrors = new StringBuilder();
for (int i = 0; i < gpMessages.Count; i++)
sErrors.AppendLine(gpMessages.GetMessage(i).Description);
Results = sErrors.ToString();
}

AO的实现过程看上去还挺复杂，但是流程还是很简要的，获取Network Analysis Layer、NAContext->设置分析条件->导入stops->计算->处理结果。结果的处理我们单独看看代码。

//Get route results from “Routes” NAClass
IFeatureClass featureClass = naContext.NAClasses.get_ItemByName("Routes") as IFeatureClass;
IFeatureCursor featureCursor = featureClass.Search(queryFilter, false);
IFeature feature = featureCursor.NextFeature();
while (feature != null)
{
IPolyline comPolyline = feature.Shape as IPolyline;
feature = featureCursor.NextFeature();
}

// Get the directions agent
INAStreetDirectionsAgent2 naStreetDirectionsAgent = (INAStreetDirectionsAgent2)routeNAContext.Agents.get_ItemByName("StreetDirectionsAgent");
naStreetDirectionsAgent.Execute(routeSet, null);
INAStreetDirections naStreetDirections = null;
INAStreetDirection2 naStreetDirection = null;
INAStreetDirectionsContainer naStreetDirectionsContainer = naStreetDirectionsAgent.DirectionsContainer;
for (int routeIndex = 0; routeIndex < naStreetDirectionsContainer.DirectionsCount; routeIndex++)
{
naStreetDirections = naStreetDirectionsContainer.get_Directions(routeIndex);
}

这几段代码是在ArcGIS Server for .NET环境下实现路径分析的功能，Server下的AO编程和Engine、Desktop有点类似，最大的区别在于创建对象的时候，Engine、Desktop创建新对象用new就可以，但是Server AO的开发必须首先获得IServerContext，然后通过CreateObject的方式。网络分析其它功能，最近设施查询、服务区域分析、OD代价矩阵、车辆路径规划、L-A的实现基本的流程和路径分析类似。