Chapter 14 Adding layers to a map

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Chapter 14 Adding layers to a map

• Advanced GIS
• Week 8
• 2005 Spring

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Procedures

• Create a layer from layer coclass
• Get data set from folder
• Associate the data set with the layer
• Add the layer to a map

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Create layers from coclass

• For examples
• Dim pRLayer as IRasterLayer
• Set pRLayer as RasterLayer
• Dim pFLayer as IFeatureLayer
• Set pFLayer as FeatureLayer

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Workspace

• The place the data is stored (folder, access
  file)
• To get a data set, you should get its workspace
  which you get from a workspace factory.
• Procedures create a workspace factory, use it to
  get a workspace, and then get the data set you
  want from the workspace.
• See page 240 for the illustration.

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Workspace Factory and Workspace

• WorkspaceFactory is an abstract class with many
  coclasses
• When you have got a workspace from a
  workspacefacotry, you get a data set from the
  workspace. Dataset, as in workspace factory, is
  an abstract class with many subclasses.

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Adding geodatabase feature class

• For example to add feature layer, you need to
  create the layer first.
• Dim pFLayer As IFeatureLayer
• Set pFLayer New FeatureLayer
• Then, to access data set, you need to create a
  Workspace Factory. Personal geodatabases are
  stored in MS Access file format. So, we create a
  MS workspace factory
• Dim pAWFactory As IWorkspaceFactory
• Set pAWFactory New AccessWorkspaceFactory

Although you are creating a MS Access workspace,
the variable is declared to IWorkspaceFactory
because of its method OpenFromFile, which
returns IWorkspace
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Workspace

• Get workspace
• Dim pFWorkspace As IFeatureWorkspace
• Set pFWorkspace pAWFactory.OpenFromFile
  (G\Students\...mdb,0)
• Get the data by running OpenFeatureClass method
• Dim FClass As IFeatureClass
• Set FClass pFWorkspace.OpenFeatureClass(Streets
  )

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byVal or byRef

• Set byVal and byRef

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Associate feature to layer and add layer to a map

• Associate a feature class with a layer by setting
  the FeatureClass property on IFeatureLayer
• Set pFlayer.FeatureClass pFClass
• Finally, add the layer to a map (see different
  method for raster image on page 255)
• Dim pMxDoc as IMxDocument
• Set pMxDoc ThisDocument
• Dim pMap As IMap
• Set pMap pMsDoc.FocusMap
• Then, Add the layer with the AddLayer method on
  IMap
• pMap.AddLayer pFLayer
• pMxDoc.ActiveView.Refresh
• pMxDoc.UpdateContents

Move layer pMap.MoveLayer pRLayer,
pMap.LayerCount-1
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Inheritance

• Class Inheritance - A class has all the
  interfaces of its superclass. For example,
  FeatureLayer has all the interfaces of it
  superclass Layer.
• Interface Inheritance one interface inherits
  the properties and methods of another interface.
• Page 264 shows example