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

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 solution, get an access token and set the API key.

   Instructions to set the API Key

   An API Key gives your app access to secure resources used in this tutorial.

   1. Go to the Create an API key tutorial to obtain a new API key access token using your ArcGIS Location Platform or ArcGIS Online account. Ensure that the following privilege is enabled: Location services > Basemaps > Basemap styles service. Copy the access token as it will be used in the next step.

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

   3. Modify the code to set the API key to the copied access token. Save and close the file.

      main.cpp

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          // 2. API key authentication: Get a long-lived access token that gives your application access to
          // ArcGIS location services. Go to the tutorial at https://links.esri.com/create-an-api-key.
          // Copy the API Key access token.
      
          const QString accessToken = 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 <QFuture>
   
   #include "LayerListModel.h"
   #include "ServiceFeatureTable.h"
   #include "FeatureLayer.h"
   

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.

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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->setViewpointAsync(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);
   

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.

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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);
   

   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);
   

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);
   

   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.

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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);
   

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.

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   Add line.Add line.

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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.

What's next?

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

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