PolygonBuilder Class

Detailed Description

Polygon geometries are immutable and cannot be changed directly once created. A polygon is a closed area shape defined by one or more parts. Each part in a polygon is a connected sequence of Segment instances that start and end at the same point (a closed ring). If a polygon has more than one ring, the rings may be separate from one another or they may nest inside one another, but they should not overlap. Note: interior rings, to make donut polygons, should be counter-clockwise in direction to be topology correct. If there is ever a doubt about the topological correctness of a polygon, call GeometryEngine::simplify(const Esri::ArcGISRuntime::Geometry&) to correct any issues.

The polygon builder allows you to change the contents of the shape using the PartCollection that you can access from the MultipartBuilder::parts. Each Part, in this PartCollection, comprises a collection of segments that make edges of the Part. You can add or remove a Part from the PartCollection, or you can create a new or edit the segment vertices of an existing Part. Use GeometryBuilder::toGeometry to return the new Polygon from the builder.

// create a polygon builder
PolygonBuilder* polygonBuilder = new PolygonBuilder(SpatialReference(3857), this);

// create a single-part polygon using x/y
polygonBuilder->addPoint(-18.0, 34.0);
polygonBuilder->addPoint(-18.0, 35.0);
polygonBuilder->addPoint(-17.0, 34.0);
Polygon singlePartPolygonXY(polygonBuilder->toGeometry());

// create a multi-part polygon with same PolygonBuilder
PartCollection* partCollection = new PartCollection(polygonBuilder->spatialReference(), this);

// create outer poly 1
Part* part1 = new Part(polygonBuilder->spatialReference(), this);
part1->addPoint(2.123456789, 3.123456789);
part1->addPoint(1.123456789, 3.123456789);
part1->addPoint(1.123456789, 1.123456789);
partCollection->addPart(part1);

// create outer poly 2
Part* part2 = new Part(polygonBuilder->spatialReference(), this);
part2->addPoint(3.123456789, 3.123456789);
part2->addPoint(4.123456789, 3.123456789);
part2->addPoint(4.123456789, 1.123456789);
partCollection->addPart(part2);

polygonBuilder->setParts(partCollection);

Polygon multipartPolygon = polygonBuilder->toPolygon();