readme.md

Create and edit geometries

Use the Geometry Editor to create new point, multipoint, polyline, or polygon geometries or to edit existing geometries by interacting with a map view.

Use case

A field worker can mark features of interest on a map using an appropriate geometry. Features such as sample or observation locations, fences or pipelines, and building footprints can be digitized using point, multipoint, polyline, and polygon geometry types. Polyline and polygon geometries can be created and edited using a vertex-based creation and editing tool (i.e. vertex locations specified explicitly via tapping), or using a freehand tool.

How to use the sample

To create a new geometry, press the button appropriate for the geometry type you want to create (i.e. points, multipoints, polyline, or polygon) and interactively tap and drag on the map view to create the geometry. To edit an existing geometry, tap the geometry to be edited in the map and then perform edits by tapping and dragging its elements. When using an appropriate tool to select a whole geometry, you can use the control handles to scale and rotate the geometry. If creating or editing polyline or polygon geometries, choose the desired creation/editing tool (i.e. VertexTool, ReticleVertexTool, FreehandTool, or one of the available ShapeTools).

When using the ReticleVertexTool, you can move the map position of the reticle by dragging and zooming the map. Insert a vertex under the reticle by tapping on the map. Move a vertex by tapping when the reticle is located over a vertex, drag the map to move the position of the reticle, then tap a second time to place the vertex.

Use the control panel to undo or redo changes made to the geometry, delete a selected element, save the geometry, stop the editing session and discard any edits, and remove all geometries from the map.

How it works

1. Create a GeometryEditor and set it to the MapView using MyMapView.GeometryEditor.
2. Start the GeometryEditor using GeometryEditor.Start(GeometryType) to create a new geometry or GeometryEditor.Start(Geometry) to edit an existing geometry.
   • If using the Geometry Editor to edit an existing geometry, the geometry must be retrieved from the graphics overlay being used to visualize the geometry prior to calling the start method. To do this:
     • Use MapView.IdentifyGraphicsOverlayAsync(...) to identify graphics at the location of a tap.
     • Access the MapView.IdentifyGraphicsOverlayAsync(...).
     • Find the desired graphic in the results.FirstOrDefault() list.
     • Access the geometry associated with the Graphic using Graphic.Geometry - this will be used in the GeometryEditor.Start(Geometry) method.
3. Create VertexTool, ReticleVertexTool, FreehandTool, or ShapeTool objects to define how the user interacts with the view to create or edit geometries, setting GeometryEditor.Tool.
4. Edit a tool's InteractionConfiguration to set the GeometryEditorScaleMode to allow either uniform or stretch scale mode.
5. Check to see if undo and redo are possible during an editing session using GeometryEditor.CanUndo and GeometryEditor.CanRedo. If it's possible, use GeometryEditor.Undo() and GeometryEditor.Redo().
6. Check whether the currently selected GeometryEditorElement can be deleted (GeometryEditor.SelectedElement.CanDelete). If the element can be deleted, delete using GeometryEditor.DeleteSelectedElement().
7. Call GeometryEditor.Stop() to finish the editing session and store the Graphic. The GeometryEditor does not automatically handle the visualization of a geometry output from an editing session. This must be done manually by propagating the geometry returned into a Graphic added to a GraphicsOverlay.
   • To create a new Graphic in the GraphicsOverlay:
     • Using Graphic(Geometry), create a new Graphic with the geometry returned by the GeometryEditor.Stop() method.
     • Append the Graphic to the GraphicsOverlay(i.e. GraphicsOverlay.Graphics.Add(Graphic)).
   • To update the geometry underlying an existing Graphic in the GraphicsOverlay:
     • Replace the existing Graphic's Geometry property with the geometry returned by the GeometryEditor.Stop() method.

Relevant API

• Geometry
• GeometryEditor
• Graphic
• GraphicsOverlay
• MapView

Additional information

The sample opens with the ArcGIS Imagery basemap centered on the island of Inis Meain (Aran Islands) in Ireland. Inis Meain comprises a landscape of interlinked stone walls, roads, buildings, archaeological sites, and geological features, producing complex geometrical relationships.

Tags

draw, edit, freehand, geometry editor, sketch, vertex