Add a feature layer

Learn how to use a URL to access and display a feature layer in a map.

A map contains layers of geographic data. A map contains a basemap layer and, optionally, one or more data layers. This tutorial shows you how to access and display a feature layer in a map. You access feature layers with an item ID or URL. You will use URLs to access the Trailheads, Trails, and Parks and Open Spaces feature layers and display them in a map.

A feature layer is a dataset in a feature service hosted in ArcGIS. Each feature layer contains features with a single geometry type (point, line, or polygon), and a set of attributes. You can use feature layers to store, access, and manage large amounts of geographic data for your applications.

Prerequisites

Choose your API

You can do this tutorial in C++ or QML. Make your selection below:

• Steps for C++
• Steps for QML

Steps for C++

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: 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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Include header files

1. Double click on Sources > Display_a_map.cpp to open the file. Include these header files to be able to create ServiceFeatureTable and FeatureLayer instances.

   Display-a-map.cpp

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   #include "Display_a_map.h"
   #include "Map.h"
   #include "MapTypes.h"
   #include "MapQuickView.h"
   #include "Point.h"
   #include "Viewpoint.h"
   #include "SpatialReference.h"
   #include "TaskWatcher.h"
   
   #include "LayerListModel.h"
   #include "ServiceFeatureTable.h"
   #include "FeatureLayer.h"
   

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Add a polygon feature layer

This tutorial will draw the map in following order:

1. ArcGISTopographic basemap style layer
2. Parks and Open Spaces (polygons)
3. Trails (lines)
4. Trailheads (points)

It is important to add feature layers in the correct order so features are displayed correctly. Polygon feature layers are typically created before lines or points, so that those features are not obscured by the polygons.

Use the FeatureLayer class to reference the Parks and Open Spaces URL and add features to the map.

1. Go to the Parks and Open Spaces URL and browse the properties of the layer. You may want to explore the Name, Type, Drawing Info, and Fields properties.

2. Within the setupViewpoint method, add the following code. Create a QUrl instance named polygonFeatureUrl using an ArcGIS feature server as the feature data source. Then create a ServiceFeatureTable named polygon_feature_table from that QUrl.

   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);
   
     const QUrl polygonFeatureUrl("https://services3.arcgis.com/GVgbJbqm8hXASVYi/ArcGIS/rest/services/Parks_and_Open_Space/FeatureServer/0");
     ServiceFeatureTable* polygon_feature_table = new ServiceFeatureTable(polygonFeatureUrl, this);
   

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3. Create a FeatureLayer instance named polygon_feature_layer, passing in polygon_feature_table as the argument. Then append your new polygon_feature_layer to the Map instance named m_map.

   Display-a-map.cpp

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     const QUrl polygonFeatureUrl("https://services3.arcgis.com/GVgbJbqm8hXASVYi/ArcGIS/rest/services/Parks_and_Open_Space/FeatureServer/0");
     ServiceFeatureTable* polygon_feature_table = new ServiceFeatureTable(polygonFeatureUrl, this);
   
     FeatureLayer* polygon_feature_layer = new FeatureLayer(polygon_feature_table, this);
     m_map->operationalLayers()->append(polygon_feature_layer);
   

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   Press <Ctrl+R> to run the app.

   You should see a map view centered in the Santa Monica Mountains, with your feature layer showing the Parks and Open Spaces layer in the map.

Add a line feature layer

Line features are typically displayed in a feature layer before points. Use the FeatureLayer class to reference the Trails URL and add features to the map, as described next.

1. Add the following code to create a QUrl instance named lineFeatureUrl using the ArcGIS feature server as the feature data source, in this case, Trails_Styled. Then create a ServiceFeatureTable named line_feature_table from that QUrl.

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     FeatureLayer* polygon_feature_layer = new FeatureLayer(polygon_feature_table, this);
     m_map->operationalLayers()->append(polygon_feature_layer);
   
     const QUrl lineFeatureUrl("https://services3.arcgis.com/GVgbJbqm8hXASVYi/ArcGIS/rest/services/Trails/FeatureServer/0");
     ServiceFeatureTable* line_feature_table = new ServiceFeatureTable(lineFeatureUrl, this);
   

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2. Create a FeatureLayer instance named line_feature_layer, passing in line_feature_table as the argument. Then append your new line_feature_layer to the Map instance named m_map.

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     const QUrl lineFeatureUrl("https://services3.arcgis.com/GVgbJbqm8hXASVYi/ArcGIS/rest/services/Trails/FeatureServer/0");
     ServiceFeatureTable* line_feature_table = new ServiceFeatureTable(lineFeatureUrl, this);
   
     FeatureLayer* line_feature_layer = new FeatureLayer(line_feature_table, this);
     m_map->operationalLayers()->append(line_feature_layer);
   

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   Press <Ctrl+R> to run the app.

   The map view should display the Parks and Open Spaces layer (polygons) and the Trails (lines) layer.

Add a point feature layer

1. Add the following code to create a QUrl instance named pointFeatureUrl using the ArcGIS feature server as the feature data source, in this case, Trailheads. Then create a ServiceFeatureTable named point_feature_table from that QUrl.

   Display-a-map.cpp

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     FeatureLayer* line_feature_layer = new FeatureLayer(line_feature_table, this);
     m_map->operationalLayers()->append(line_feature_layer);
   
     const QUrl pointFeatureUrl("https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Trailheads/FeatureServer/0");
     ServiceFeatureTable* point_feature_table= new ServiceFeatureTable(pointFeatureUrl, this);
   

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2. Add the following two lines of code to create a FeatureLayer, passing in point_feature_table as the argument. Then append your FeatureLayer to the Map instance named m_map.

   Display-a-map.cpp

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     const QUrl pointFeatureUrl("https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Trailheads/FeatureServer/0");
     ServiceFeatureTable* point_feature_table= new ServiceFeatureTable(pointFeatureUrl, this);
   
     FeatureLayer* point_feature_layer = new FeatureLayer(point_feature_table, this);
     m_map->operationalLayers()->append(point_feature_layer);
   

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   Press <Ctrl+R> to run the app.

The map view should display all three feature layers in the map. Double-click, drag, and scroll the mouse wheel over the map view to explore the map.

To explore other tutorials, see What's next.

Steps for QML

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: 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("");
      

      Expand

This tutorial will draw the map in following order:

1. ArcGISTopographic basemap style layer
2. Parks and Open Spaces (polygons)
3. Trails (lines)
4. Trailheads (points)

To display each of three new feature layers (also known as operational layers) on top of the current basemap, you will create a ServiceFeatureTable using a URL to reference datasets hosted in ArcGIS Online. Each service feature table will become an argument to a FeatureLayer which will be displayed on the map.

Add a polygon feature layer

It is important to add feature layers in the correct order so that features are displayed correctly. Polygon feature layers are typically created before lines or points, so that those features are not obscured by the polygons.

1. Open a web browser and go to the feature service URL for Parks and Open Spaces. The service page provides information such as the geometry type, the geographic extent, the minimum and maximum scale at which features are visible, and the attributes (fields) it contains. You can preview the layer by clicking on ArcGIS.com Map in the View In: list at the top of the page.

2. A Polygon geometry represents the shape and location of an area, for example, a country, island, or a lake. A polygon can be used as the geometry of features and graphics, or as input or output of tasks or geoprocessing operations. In this example, our polygons are delivered by a feature service. Use the FeatureLayer class and ServiceFeatureTable class to display the Parks and Open Spaces polygons. Open the main.qml file and add the following code where shown.

   main.qml

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           // add a map to the mapview
           Map {
               // add the ArcGISTopographic basemap to the map
               initBasemapStyle: Enums.BasemapStyleArcGISTopographic
               initialViewpoint: viewpoint
   
               // Add the polygon feature layer
               FeatureLayer {
                   ServiceFeatureTable {
                       url: "https://services3.arcgis.com/GVgbJbqm8hXASVYi/ArcGIS/rest/services/Parks_and_Open_Space/FeatureServer/0"
                   }
                }
   

   Expand

   Press <Ctrl+R> to run the app.

   You should see a map view centered in the Santa Monica Mountains, with your feature layer showing the Parks and Open Spaces layer as gray polygons in the map.

Add a line feature layer

Line features are typically displayed in a feature layer before points.

1. Use the FeatureLayer class and ServiceFeatureTable class to display the Trails with the following code.

   main.qml

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               // Add the polygon feature layer
               FeatureLayer {
                   ServiceFeatureTable {
                       url: "https://services3.arcgis.com/GVgbJbqm8hXASVYi/ArcGIS/rest/services/Parks_and_Open_Space/FeatureServer/0"
                   }
                }
   
                // Add the line feature layer
                 FeatureLayer {
                   ServiceFeatureTable {
                       url: "https://services3.arcgis.com/GVgbJbqm8hXASVYi/ArcGIS/rest/services/Trails/FeatureServer/0"
                   }
                }
   

   Expand

   Press <Ctrl+R> to run the app.

The map view should display the Parks and Open Spaces (polygons) feature layer and the Trails (lines) feature layer.

Add a point feature layer

Point geometries represent discrete locations or entities, such as a geocoded house address, the location of a water meter in a water utility network, a moving vehicle, and so on. In this example, our pre-defined points are being delivered by a feature service.

1. Use the FeatureLayer class and ServiceFeatureTable class to display the Trailheads with the following code.

   main.qml

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   Add line.Add line.Add line.Add line.Add line.Add line.

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                // Add the line feature layer
                 FeatureLayer {
                   ServiceFeatureTable {
                       url: "https://services3.arcgis.com/GVgbJbqm8hXASVYi/ArcGIS/rest/services/Trails/FeatureServer/0"
                   }
                }
   
                // Add the points feature layer
                 FeatureLayer {
                   ServiceFeatureTable {
                       url: "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Trailheads/FeatureServer/0"
                   }
                }
   

   Expand

   Press <Ctrl+R> to run the app.

The map view should display all three feature layers in the map. Double-click, drag, and scroll the mouse wheel over the map view to explore the map.

What's next?

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

Not all tutorials listed have instructions for QML.

• Add a point, line, and polygon
• Search for an address
• Get a route and directions
• Find a route and directions
• Display a scene