Arc: Getting Layers

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Arc Getting Layers

• Dr Andy Evans

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ArcMap IMXDocument methods

• Used for getting data
• getActiveView() i.e. layout view or data view
  data.
• getFocusMap() i.e. currently selected/shown
  map.
• getMaps() i.e. all maps.
• getSelectedItem() i.e. that the user has picked.
• getSelectedLayer() i.e. that the user has picked.
• Documents also implement IDocument, the main use
  of which is programmatically controlling toolbars.

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Getting data
Document (.mxd file)
Map
AttributeTable
FID Data
1 234
2 875
Layer
Feature
234
Values
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Getting a Map

• A Map contains all the data and features in the
  Data View or each Layout View frame.
• import com.esri.arcgis.carto.
• IMxDocument mxDocument (IMxDocument)app.getD
  ocument()
• IMap mxDoc mxDocument.getFocusMap()
• FocusMap is the one visible in data view or
  selected in layout view.

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Getting all Maps

• You can also get an Object containing all the
  Maps.
• IMaps maps mxDoc.getMaps()

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IMaps

• You can loop through all the IMap Interface
  objects in an IMaps Interface object using its
  .getCount and .getItem methods.
• IMap map null
• for (int i 0 i lt maps.getCount i)
• map maps.getItem(i)
• Other IMaps methods include
• add(IMap), create(), remove(IMap),
  removeAt(index), Reset Remove all.

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Getting data

• Its rare we want to get data out of a Map. Its
  more usual to get data from a Layer (a
  Coverage, FeatureDataset, Image etc.).

Map
AttributeTable
FID Data
1 234
2 875
Layer
Feature
234
Values
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Getting Layers I

• If you know what the type of the Layers are, you
  can get them thus
• // Assuming we've got a IMap object "map".
• ILayer layer null
• for (int i0 i lt map.getLayerCount() i)
• layer map.getLayer(i)
• // Do something

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Enumerations

• Objects containing lists of other objects. Like a
  1D array.
• Arc uses them to return arrays of data to you.
• Have a next method to get the next object.
• Also a reset method to return to the start.
• ArcObject types have different Enumerations.
• e.g. IEnumLayer is the Interface for a set of
  Layers.

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Standard use of Enumerations

• IEnumSomething enumSomething someEnumGett
  ingMethod()
• enumSomething.reset()
• SomeClass variable enumSomething.next()
• while (variable ! null)
• \\Do stuff with variable
• variable enumSomething.next()
• Note we get the first variable first, then do
  something with it, before getting the next and
  checking whether it is null.

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Getting Layers II

• Get an Enumeration of Layers
• IEnumLayer enumLayer
• map.getLayers(null,true)
• enumLayer.reset()
• ILayer layer enumLayer.next()
• while (layer ! null)
• \\ Do something with the ILayer
• layer enumLayer.next()

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Types of Layer

• Remember however that we can add many things as
  Layers (images, data, etc.).
• Main types
• IFeatureLayer
• IGeoFeatureLayer
• IGraphicsLayer
• Others include more specific FeatureLayers,
  FDOGraphicsLayers (Annotation), TinLayer,
  RasterLayer, and CoverageAnnotationLayer.
• If we dont know the layers in the document we
  may need to check for a specific type.

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The instanceof keyword

• You can check whether an object implements an
  Interface using Javas instanceof keyword.
• For example, if the users selected something in
  ArcMap's tree of contents, you can test whether
  its a GeoFeatureLayer, thus
• // Assuming weve got an enumeration of Layers.
• IGeoFeatureLayer featLayer null
• ILayer layer enumLayer.next()
• while (layer ! null)
• if (layer instanceof IGeoFeatureLayer)
• featLayer (IGeoFeatureLayer) layer
• //Do something with featLayer
• layer enumLayer.next()