ArcGIS Pro SDK 实时要素类

实时要素类

从实时数据存储连接到实时要素类

var url = "https://geoeventsample1.esri.com:6443/arcgis/rest/services/AirportTraffics/StreamServer";
     
await QueuedTask.Run(() =>
{
  var realtimeServiceConProp = new RealtimeServiceConnectionProperties(
                                   new Uri(url),
                                   RealtimeDatastoreType.StreamService
                                );
  using (var realtimeDatastore = new RealtimeDatastore(realtimeServiceConProp))
  {
    //A Realtime data store only contains **one** Realtime feature class (or table)
    var name = realtimeDatastore.GetTableNames().First();
    using (var realtimeFeatureClass = realtimeDatastore.OpenTable(name) as RealtimeFeatureClass)
    {
      //feature class, by default, is not streaming (opposite of the stream layer)
      realtimeFeatureClass.StartStreaming();
      //TODO use the feature class
      //...
    }
  }

});

检查实时要素类是否可识别轨迹

using (var rfc = streamLayer.GetFeatureClass())
using (var rfc_def = rfc.GetDefinition())
{
  if (rfc_def.HasTrackIDField())
  {
    //Track aware
  }
}

从实时要素类获取追踪 ID 字段

//Must be on QueuedTask
using (var rfc = streamLayer.GetFeatureClass())
using (var rfc_def = rfc.GetDefinition())
{
  if (rfc_def.HasTrackIDField())
  {
    var fld_name = rfc_def.GetTrackIDField();

  }
}

订阅流数据

//Note: with feature class we can also use a System Task to subscribe and
//process rows
await QueuedTask.Run(async () =>
{
  // or var rfc = realtimeDatastore.OpenTable(name) as RealtimeFeatureClass
  using (var rfc = streamLayer.GetFeatureClass())
  {
    //non-recycling cursor - 2nd param "false"
    //subscribe, pre-existing rows are not searched
    using (var rc = rfc.Subscribe(qfilter, false))
    {
      SpatialQueryFilter spatialFilter = new SpatialQueryFilter();
      //waiting for new features to be streamed
      //default is no cancellation
      while (await rc.WaitForRowsAsync())
      {
        while (rc.MoveNext())
        {
          using (var row = rc.Current)
          {
            switch (row.GetRowSource())
            {
              case RealtimeRowSource.EventInsert:
                //getting geometry from new events as they arrive
                Polygon poly = ((RealtimeFeature)row).GetShape() as Polygon;

                //using the geometry to select features from another feature layer
                spatialFilter.FilterGeometry = poly;//project poly if needed...
                countyFeatureLayer.Select(spatialFilter);
                continue;
              default:
                continue;
            }
          }                  
        }
      }
    }//row cursor is disposed. row cursor is unsubscribed
  }
});

搜索现有数据并订阅流数据

//Note we can use System Task with the Realtime feature class
//for subscribe
await System.Threading.Tasks.Task.Run(async () =>
// or use ... QueuedTask.Run()
{
  using (var rfc = streamLayer.GetFeatureClass())
  {
    //non-recycling cursor - 2nd param "false"
    using (var rc = rfc.SearchAndSubscribe(qfilter, false))
    {
      //waiting for new features to be streamed
      //default is no cancellation
      while (await rc.WaitForRowsAsync())
      {
        //pre-existing rows will be retrieved that were searched
        while (rc.MoveNext())
        {
          using (var row = rc.Current)
          {
            var row_source = row.GetRowSource();
            switch (row_source)
            {
              case RealtimeRowSource.EventDelete:
                //TODO - handle deletes
                break;
              case RealtimeRowSource.EventInsert:
                //TODO handle inserts
                break;
              case RealtimeRowSource.PreExisting:
                //TODO handle pre-existing rows
                break;
            }
          }
        }
      }
    }//row cursor is disposed. row cursor is unsubscribed
  }
});

搜索和订阅取消

await System.Threading.Tasks.Task.Run(async () =>
// or use ... QueuedTask.Run()
{
  using (var rfc = streamLayer.GetFeatureClass())
  {
    //Recycling cursor - 2nd param "true"
    using (var rc = rfc.SearchAndSubscribe(qfilter, true))
    {
      //auto-cancel after 20 seconds
      var cancel = new CancellationTokenSource(new TimeSpan(0, 0, 20));
      //catch TaskCanceledException
      try
      {
        while (await rc.WaitForRowsAsync(cancel.Token))
        {
          //check for row events
          while (rc.MoveNext())
          {
            using (var record = rc.Current)
            {
              //etc
            }
          }
        }
      }
      catch(TaskCanceledException tce)
      {
        //Handle cancellation as needed
      }
      cancel.Dispose();
    }
  }
});

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