Add a point, line, and polygon

Learn how to display point, line, and polygon graphics in a map.

You typically use graphics to display geographic data that is not connected to a database and that is not persisted, like highlighting a route between two locations, displaying a search buffer around a point, or tracking the location of a vehicle in real-time. Graphics are composed of a geometry, symbol, and attributes.

In this tutorial, you display points, lines, and polygons on a map as graphics.

Prerequisites

Open the project in Qt Creator

1. To start this tutorial, complete the Display a map tutorial or download and unzip the solution.

2. Open the display_a_map project in Qt Creator.

3. If you downloaded the Display a map solution, set your API key.

   More info

   An API Key enables access to services, web maps, and web scenes hosted in ArcGIS Online.

   1. Go to your developer dashboard to get your API key. For these tutorials, use your default API key. It is scoped to include all of the services demonstrated in the tutorials.

   2. In the Projects window, in the Sources folder, open the main.cpp file.

   3. Modify the code to set the API key. Paste the API key, acquired from your dashboard, between the quotes. Then save and close the file.

      main.cpp

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          // 2. API key authentication: Get a permanent key that gives your application access to Esri
          // location services. Create a new API key or access existing API keys from
          // your ArcGIS for Developers dashboard (https://links.esri.com/arcgis-api-keys).
      
          const QString apiKey = QString("");
      

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Add GraphicsOverlay class, declare member function

GraphicsOverlay is a container for temporary graphics to display on your map view. The graphics drawn in graphics overlays are created at runtime and are not persisted when your application closes. Learn more about GraphicsOverlay.

1. In the display_a_map project, double click Headers > Display_a_map.h to open the file. Add the GraphicsOverlay class to the namespace ArcGISRuntime declaration.

   Display_a_map.h

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   class Map;
   class MapQuickView;
   
   class GraphicsOverlay;
   }
   

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2. Add the createGraphics private member function declaration. Then save and close the header file.

   Display_a_map.h

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   private:
       Esri::ArcGISRuntime::MapQuickView* mapView() const;
       void setMapView(Esri::ArcGISRuntime::MapQuickView* mapView);
       void setupViewpoint();
   
       void createGraphics(Esri::ArcGISRuntime::GraphicsOverlay* overlay);
   

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Create a graphics overlay

A graphics overlay is a container for graphics. It is added to a map view to display graphics on a map. You can add more than one graphics overlay to a map view. Graphics overlays are displayed on top of all the other layers.

1. Double click on Sources > Display_a_map.cpp to open the file. Include the classes shown.

   Display_a_map.cpp

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   #include "Display_a_map.h"
   #include "Map.h"
   #include "MapQuickView.h"
   #include "MapTypes.h"
   #include "Point.h"
   #include "SpatialReference.h"
   #include "TaskWatcher.h"
   #include "Viewpoint.h"
   
   #include "Graphic.h"
   #include "GraphicListModel.h"
   #include "GraphicsOverlay.h"
   #include "GraphicsOverlayListModel.h"
   #include "PolylineBuilder.h"
   #include "PolygonBuilder.h"
   #include "SimpleFillSymbol.h"
   #include "SimpleLineSymbol.h"
   #include "SimpleMarkerSymbol.h"
   #include "SymbolTypes.h"
   

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2. In the Display_a_map::setMapView member function, add three lines of code to create a GraphicsOverlay, call the createGraphics method (implemented in following steps), and append the overlay to the map view.

   Display_a_map.cpp

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   // Set the view (created in QML)
   void Display_a_map::setMapView(MapQuickView* mapView)
   {
       if (!mapView || mapView == m_mapView)
       {
           return;
       }
   
       m_mapView = mapView;
       m_mapView->setMap(m_map);
       setupViewpoint();
   
       GraphicsOverlay* overlay = new GraphicsOverlay(this);
       createGraphics(overlay);
       m_mapView->graphicsOverlays()->append(overlay);
   

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3. Create a new method named Display_a_map::createGraphics, right after the Display_a_map::setupViewpoint method.

   Display_a_map.cpp

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   void Display_a_map::setupViewpoint()
   {
       const Point center(-118.80543, 34.02700, SpatialReference::wgs84());
       const Viewpoint viewpoint(center, 100000.0);
       m_mapView->setViewpoint(viewpoint);
   }
   
   void Display_a_map::createGraphics(GraphicsOverlay *overlay)
   {
   
   }
   

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Add a point graphic

A point graphic is created using a point and a marker symbol. A point is defined with x and y coordinates for longitude and latitude coordinates, and a spatial reference. The spatial reference is WGS84.

1. Create a Point and a SimpleMarkerSymbol. To create the Point, provide longitude (x) and latitude (y) coordinates, and a SpatialReference.

   More info

   Point graphics support a number of symbol types such as SimpleMarkerSymbol, PictureMarkerSymbol_qt and TextSymbol. See Symbol in the API documentation to learn more about symbols.

   Display_a_map.cpp

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   void Display_a_map::setupViewpoint()
   {
       const Point center(-118.80543, 34.02700, SpatialReference::wgs84());
       const Viewpoint viewpoint(center, 100000.0);
       m_mapView->setViewpoint(viewpoint);
   }
   
   void Display_a_map::createGraphics(GraphicsOverlay *overlay)
   {
   
       // Create a point
       const Point dume_beach(-118.80657463861, 34.0005930608889, SpatialReference::wgs84());
       // Create symbols for the point
       SimpleLineSymbol* point_outline = new SimpleLineSymbol(SimpleLineSymbolStyle::Solid, QColor("blue"), 3, this);
       SimpleMarkerSymbol* point_symbol = new SimpleMarkerSymbol(SimpleMarkerSymbolStyle::Circle, QColor("red"), 10, this);
       point_symbol->setOutline(point_outline);
   
       // Create a graphic to display the point with its symbology
       Graphic* point_graphic = new Graphic(dume_beach, point_symbol, this);
       // Add point graphic to the graphics overlay
       overlay->graphics()->append(point_graphic);
   

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2. Press Ctrl + R to run the app.

You should see a point graphic at Point Dume State Beach, California.

Add a polyline graphic

A line graphic is created using a polyline and a line symbol. A polyline is defined as a sequence of points.

1. Create a Polyline and a SimpleLineSymbol.

   To create the Polyline, create a new PointCollection with a SpatialReference and use PolylineBuilder to add a new Point objects to it. Add the highlighted code.

   Display_a_map.cpp

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       // Create a graphic to display the point with its symbology
       Graphic* point_graphic = new Graphic(dume_beach, point_symbol, this);
       // Add point graphic to the graphics overlay
       overlay->graphics()->append(point_graphic);
   
       // Create a line
       PolylineBuilder* polyline_builder = new PolylineBuilder(SpatialReference::wgs84(), this);
       polyline_builder->addPoint(-118.8215, 34.0140);
       polyline_builder->addPoint(-118.8149, 34.0081);
       polyline_builder->addPoint(-118.8089, 34.0017);
       // Create a symbol for the line
       SimpleLineSymbol* line_symbol = new SimpleLineSymbol(SimpleLineSymbolStyle::Solid, QColor(Qt::blue), 3, this);
   
       // Create a graphic to display the line with its symbology
       Graphic* polyline_graphic = new Graphic(polyline_builder->toGeometry(), line_symbol, this);
       // Add line graphic to the graphics overlay
       overlay->graphics()->append(polyline_graphic);
   

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2. Press Ctrl + R to run the app.

You should see a point and a line graphic along Westward Beach.

Add a polygon graphic

A polygon graphic is created using a polygon and a fill symbol. A polygon is defined as a sequence of points that describe a closed boundary.

1. Create a Polygon and a SimpleFillSymbol. To create the Polygon, create a new PointCollection with a SpatialReference and use PolygonBuilder to add new Point objects to it. Add the highlighted code.

   Display_a_map.cpp

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       // Create a graphic to display the line with its symbology
       Graphic* polyline_graphic = new Graphic(polyline_builder->toGeometry(), line_symbol, this);
       // Add line graphic to the graphics overlay
       overlay->graphics()->append(polyline_graphic);
   
       // Create a list of points to make up the polygon
       const QList<Point> points = {
           Point(-118.8190, 34.0138),
           Point(-118.8068, 34.0216),
           Point(-118.7914, 34.0164),
           Point(-118.7960, 34.0086),
           Point(-118.8086, 34.0035),
       };
       // Create a polygon using the list of points above
       PolygonBuilder* polygon_builder = new PolygonBuilder(SpatialReference::wgs84(), this);
       polygon_builder->addPoints(points);
       // Create symbols for the polygon
       SimpleLineSymbol* polygon_line_symbol = new SimpleLineSymbol(SimpleLineSymbolStyle::Solid, QColor(Qt::blue), 3, this);
       SimpleFillSymbol* fill_symbol = new SimpleFillSymbol(SimpleFillSymbolStyle::Solid, QColor(Qt::yellow), polygon_line_symbol, this);
       // Create a graphic to display the polygon with its symbology
       Graphic* polygon_graphic = new Graphic(polygon_builder->toGeometry(), fill_symbol, this);
       // Add polygon graphic to the graphics overlay
       overlay->graphics()->append(polygon_graphic);
   

   Expand

2. Press Ctrl + R to run the app.

You should see a point, line, and polygon graphic around Mahou Riviera in the Santa Monica Mountains.

What's next?

Learn how to use additional API features, ArcGIS location services, and ArcGIS tools in these tutorials:

• Add a feature layer
• Search for an address
• Find a route and directions
• Display a web map
• Display a scene