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

Before starting this tutorial:

You need an ArcGIS Location Platform or ArcGIS Online account.
Your system meets the system requirements.
The ArcGIS Maps SDK for Qt, version 200.6.0 or later is installed.
The Qt 6.5.6 software development framework is installed.

Develop or Download

You have two options for completing this tutorial:

Option 1: Develop the code or
Option 2: Download the completed solution

Option 1: Develop the code

To start the tutorial, complete the Display a map tutorial. This creates a map to display the Santa Monica Mountains in California using the topographic basemap from the ArcGIS basemap styles service.

Open a Qt Creator project

Open the project you created by completing the Display a map tutorial.
Continue with the following instructions to use a URL to access and display a feature layer in a map.

Include header files

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:

ArcGISTopographic basemap style layer
Parks and Open Spaces (polygons)
Trails (lines)
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.

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.

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->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);

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);

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.

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.

Display-a-map.cpp
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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);

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.

Display-a-map.cpp
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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

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);

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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  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.

Alternatively, you can download the tutorial solution, as follows.

Option 2: Download the solution

Click the Download solution link under Solution and unzip the file to a location on your machine.
Open the project in Qt Creator.

Since the downloaded solution does not contain authentication credentials, you must set up authentication to create the developer credentials and add them to the project.

Set up authentication

To access the secure ArcGIS location services used in this tutorial, you must implement API key authentication using an ArcGIS Location Platform or an ArcGIS Online account.

Create a new API key access token with privileges to access the secure resources used in this tutorial.

Complete the Create an API key tutorial and create an API key with the following privilege(s):
- Privileges
  - Location services > Basemaps
Copy and paste the API key access token into a safe location. It will be used in a later step.

Set developer credentials in the solution

To allow your app users to access ArcGIS location services, use the developer credentials that you created in the Set up authentication step to authenticate requests for resources.

In the Projects window, go to the Sources folder
Open the main.cpp file.

Modify the code to set the accessToken using your API key access token.

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("");

Save and close the file.

Best Practice: The access token is stored directly in the code as a convenience for this tutorial. Do not store credentials directly in source code in a production environment.

Run the solution

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: