1. Jun Liang, Geography @ UNC
Lecture 4
An example for changing a layer’s Name
Before you write code for this purpose, you will need to know:
The two default objects, which you can use without create, or define them – Application, and ThisDocument
The general path you can reach a layer object from the two existing objects.
2018/11/21
Jun Liang, UNC

2. Changing a layer’s Name (Cont.)
Application
MxDocument *
Map *
Layer
FeatureLayer
RasterLayerr
2018/11/21
Jun Liang, UNC

3. Changing a layer’s Name (Cont.)
Which layer? To simplify the task, we will work on the first layer, from current map (focus map)
(1) Initial Variable: ThisDocument(MxDocument)
(2) To work with focus map, you will need to use IMxDocument interface. Please check MxDocument class, and find the interface which includes “focusMap” property.
(3) To access focus map object, you will need to define a IMap (Why?) interface variable, and initialize it with…
2018/11/21
Jun Liang, UNC

4. Changing a layer’s Name (Cont.)
(4) Now you can access layer objects through IMap interface variable (pMap). Check IMap definition in OMD and see how you can access the first layer.
(5) Before you can access the first layer object in focus map, you need to define a Layer interface variable, which one if you want to change its name? Check it from Map Layer Object Model. Here an ILayer interface variable is needed.
(6) Initialize the pLayer interface variable using pMap.
(7) pMxDoc.UpdateContents is necessary to update TOC.
2018/11/21
Jun Liang, UNC

5. A little more than changing name
Instead of changing an arbitrary layer’s name from current active map, you will list available maps and ask user to choose, and then list available layers and ask user to choose, then ask user to type a new name for that layer.
2018/11/21
Jun Liang, UNC

6. Jun Liang, Geography @ UNC
Tools
Recall you can create four different UI controls from customize window:
Button (Examples – buttons to change background color)
Tool
EditBox
ComboBox
What is the difference between button and tool?
2018/11/21
Jun Liang, UNC

7. Reporting Coordinates
What will you choose to report mouse’s coordinates? Button or Tool?
Add some data to your Arcmap document.
Create a tool and add a MouseDown event procedure for it.
Use MsgBox to report its X & Y coordinates.
2018/11/21
Jun Liang, UNC

8. Reporting Coordinates (Cont.)
Notice – MouseDown event only reports coordinates in pixels. If you want to report coordinates in map units, you will need to use ArcObjects programming.
Coclass Point and its Interface Ipoint
MxDocument class (its Object – ThisDocument) has CurrentLocation (IPoint), which will report coordinates in map units. So how can you access this property?
2018/11/21
Jun Liang, UNC

9. Reporting Coordinates (Cont.)
Access CurrentLocation fron ThisDocument object:
Dim pMxDoc As IMxDocument
Set pMxDoc = ThisDocument
Dim pPoint As IPoint
Set pPoint = pMxDoc.CurrentLocation
MsgBox “Longitude: “ & pPoint.X & “, Latitude: “ & pPoint.Y
You may also change cursor’s look by using _CursorID Function
You can change _CursorID’s value to refer to different cursor
2018/11/21
Jun Liang, UNC

10. Reporting Coordinates (Cont.)
Show Message in status bar:
IStatus is a member of Application Class. (Check diagram to see their relationship). And you can access Istatus by the following line:
Dim pStatus As IStatusBar
Set pStatus = Application.StatusBar
pStatus.Message(0) = “Latitude: “ & pPoint.y & “, Longitude: “ & _ pPoint.x
You may test the code in the mousemove event procedure.
2018/11/21
Jun Liang, UNC

11. Jun Liang, Geography @ UNC
Drawing Graphics
Graphics belong to Element abstract class, and both maps and pagelayouts are composed of Elements. Each has an IGraphicsContainer interface with methods.
MxDocument *
IGraphicContainer
Map
IGraphicContainer
PageLayout * *
Element
Element
2018/11/21
Jun Liang, UNC

12. Drawing Graphics (Cont.)
Geometry
Element
Color
Symbol
GraphicElement
FrameElement
LineElement
TextElement
MarkerElement
PolygonElement
To make graphics on a map, you create objects out of the coclass under GraphicElement.
2018/11/21
Jun Liang, UNC

13. Drawing Graphics (Cont.)
Point
Geometry
Line
Polygon
Suppose you want to create a marker element to mark a city, what will be the procedures to do this?
2018/11/21
Jun Liang, UNC

14. Drawing Graphics (Cont.)
TextSymbol
Symbol
ArrowMarkerSymbol
MarkerSymbol
SimpleMarkerSymbol
LineSymbol
CartographicLineSymbol
SimpleSymbol
FillSymbol
SimpleFillSymbol
3DChartSymbol
BarChartSymbol
2018/11/21
Jun Liang, UNC

15. Using TypeOf Statements
You might receive “type mismatch” error if you write code for a vector layor/dataset, when the user tries to apply it to a raster layer/dataset. This can be prevented by using TypeOf statement:
If TypeOf pLayer Is IRasterLayer Then
…………….
Else
……………..
EndIf
2018/11/21
Jun Liang, UNC