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Showing content from https://developers.arcgis.com/kotlin/layers/tutorials/add-a-feature-layer/ below:

Add a feature layer | ArcGIS Maps SDK for Kotlin

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.

In this tutorial, you use URLs to access and display three different feature layers hosted in ArcGIS Online:

• Trailheads (points)
• Trails (lines)
• Parks and Open Spaces (polygons)

To learn how to publish your own data as a hosted feature layer, visit Data hosting.

Before starting this tutorial, you need the following:

1. An ArcGIS Location Platform or ArcGIS Online account.

2. A development and deployment environment that meets the system requirements.

3. An IDE for Android development in Kotlin.

It is recommended that you use the latest stable version Android Studio to create this tutorial app. The code described in the steps below, however, should work in any up-to-date Android IDE that supports Kotlin.

You have two options for completing this tutorial:

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

1. Open the project you created by completing the Display a map tutorial.

2. Continue with the following instructions to use a URL to access and display a feature layer in a map.

3. Modify the old project for use in this new tutorial.

   1. On your file system, delete the .idea folder, if present, at the top level of your project.

   2. In the Android view, open app > res > values > strings.xml.

      In the <string name="app_name"> element, change the text content to Add a feature layer.

      strings.xml

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      <resources>
          <string name="app_name">Add a feature layer</string>
      </resources>

   3. In the Android view, open Gradle Scripts > settings.gradle.kts.

      Change the value of rootProject.name to "Add a feature layer".

      settings.gradle.kts

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      dependencyResolutionManagement {
          repositoriesMode.set(RepositoriesMode.FAIL_ON_PROJECT_REPOS)
          repositories {
              google()
              mavenCentral()
              maven { url = uri("https://esri.jfrog.io/artifactory/arcgis") }
          }
      }
      
      rootProject.name = "Add a feature layer"
      include(":app")

   4. Click File > Sync Project with Gradle files. Android Studio will recognize your changes and create a new .idea folder.

In MainScreen.kt, replace the import statements with the imports needed for this tutorial.

MainScreen.kt

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@file:OptIn(ExperimentalMaterial3Api::class)

package com.example.app.screens

import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.padding
import androidx.compose.material3.ExperimentalMaterial3Api
import androidx.compose.material3.Scaffold
import androidx.compose.material3.Text
import androidx.compose.material3.TopAppBar
import androidx.compose.runtime.Composable
import androidx.compose.runtime.remember
import androidx.compose.ui.Modifier
import androidx.compose.ui.res.stringResource
import com.arcgismaps.data.ServiceFeatureTable
import com.arcgismaps.mapping.ArcGISMap
import com.arcgismaps.mapping.BasemapStyle
import com.arcgismaps.mapping.Viewpoint
import com.arcgismaps.mapping.layers.FeatureLayer
import com.arcgismaps.toolkit.geoviewcompose.MapView
import com.example.app.R

In MainScreen.kt, inside the top-level function createMap(): Modify the Viewpoint constructor call so it passes a scale parameter more appropriate to tutorial.

MainScreen.kt

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fun createMap(): ArcGISMap {

    return ArcGISMap(BasemapStyle.ArcGISTopographic).apply {
        initialViewpoint = Viewpoint(
            latitude = 34.0270,
            longitude = -118.8050,

            scale = 200000.0

        )

    }

}

To display three new data layers (also known as operational layers) on top of the current basemap, you will create ServiceFeatureTables using URLs to reference datasets hosted in ArcGIS Online.

1. Open a browser and navigate to the URL for Parks and Open Spaces to view metadata about the layer. To display the layer in your app, you only need the URL.

   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 Map Viewer at the top of the page.

2. In createMap(), before the code that creates the ArcGISMap, do the following.

   1. Create strings that hold the URLs to the hosted layers. The URLs are: Trailheads (points), Trails (lines), and Parks and Open Spaces (polygons).

      MainScreen.kt

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      fun createMap(): ArcGISMap {
      
          val parksUrl =
              "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Parks_and_Open_Space_Styled/FeatureServer/0"
          val trailsUrl =
              "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Trails_Styled/FeatureServer/0"
          val trailHeadsUrl =
              "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Trailheads_Styled/FeatureServer/0"
      
          return ArcGISMap(BasemapStyle.ArcGISTopographic).apply {
              initialViewpoint = Viewpoint(
                  latitude = 34.0270,
                  longitude = -118.8050,
      
                  scale = 200000.0
      
              )
      
          }
      
      }

   2. Create three ServiceFeatureTable objects, using a string URL to reference the datasets.

      MainScreen.kt

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      fun createMap(): ArcGISMap {
      
          val parksUrl =
              "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Parks_and_Open_Space_Styled/FeatureServer/0"
          val trailsUrl =
              "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Trails_Styled/FeatureServer/0"
          val trailHeadsUrl =
              "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Trailheads_Styled/FeatureServer/0"
      
          val parksServiceFeatureTable = ServiceFeatureTable(parksUrl)
          val trailsServiceFeatureTable = ServiceFeatureTable(trailsUrl)
          val trailHeadsServiceFeatureTable = ServiceFeatureTable(trailHeadsUrl)
      
          return ArcGISMap(BasemapStyle.ArcGISTopographic).apply {
              initialViewpoint = Viewpoint(
                  latitude = 34.0270,
                  longitude = -118.8050,
      
                  scale = 200000.0
      
              )
      
          }
      
      }

   3. You will use FeatureLayers to display the hosted layers on top of the basemap.

      Create three new FeatureLayers using FeatureLayer.createWithFeatureTable(), to which you pass a service feature table.

      MainScreen.kt

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      fun createMap(): ArcGISMap {
      
          val parksUrl =
              "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Parks_and_Open_Space_Styled/FeatureServer/0"
          val trailsUrl =
              "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Trails_Styled/FeatureServer/0"
          val trailHeadsUrl =
              "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Trailheads_Styled/FeatureServer/0"
      
          val parksServiceFeatureTable = ServiceFeatureTable(parksUrl)
          val trailsServiceFeatureTable = ServiceFeatureTable(trailsUrl)
          val trailHeadsServiceFeatureTable = ServiceFeatureTable(trailHeadsUrl)
      
          val featureLayerPark = FeatureLayer.createWithFeatureTable(parksServiceFeatureTable)
          val featureLayerTrail = FeatureLayer.createWithFeatureTable(trailsServiceFeatureTable)
          val featureLayerTrailHead = FeatureLayer.createWithFeatureTable(trailHeadsServiceFeatureTable)
      
          return ArcGISMap(BasemapStyle.ArcGISTopographic).apply {
              initialViewpoint = Viewpoint(
                  latitude = 34.0270,
                  longitude = -118.8050,
      
                  scale = 200000.0
      
              )
      
          }
      
      }

3. In the apply block for ArcGISMap, create a list of these three FeatureLayers, and add them to the map's operationalLayers using addAll().

   MainScreen.kt

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   fun createMap(): ArcGISMap {
   
       val parksUrl =
           "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Parks_and_Open_Space_Styled/FeatureServer/0"
       val trailsUrl =
           "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Trails_Styled/FeatureServer/0"
       val trailHeadsUrl =
           "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Trailheads_Styled/FeatureServer/0"
   
       val parksServiceFeatureTable = ServiceFeatureTable(parksUrl)
       val trailsServiceFeatureTable = ServiceFeatureTable(trailsUrl)
       val trailHeadsServiceFeatureTable = ServiceFeatureTable(trailHeadsUrl)
   
       val featureLayerPark = FeatureLayer.createWithFeatureTable(parksServiceFeatureTable)
       val featureLayerTrail = FeatureLayer.createWithFeatureTable(trailsServiceFeatureTable)
       val featureLayerTrailHead = FeatureLayer.createWithFeatureTable(trailHeadsServiceFeatureTable)
   
       return ArcGISMap(BasemapStyle.ArcGISTopographic).apply {
           initialViewpoint = Viewpoint(
               latitude = 34.0270,
               longitude = -118.8050,
   
               scale = 200000.0
   
           )
   
           operationalLayers.addAll(
               listOf(
                   featureLayerPark,
                   featureLayerTrail,
                   featureLayerTrailHead
               )
           )
   
       }
   
   }

4. Click Run > Run > app to run the app.

You should see point features (representing trailheads) draw on the map for an area in the Santa Monica Mountains in southern California.

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

1. Click the Download solution link in the right-hand side of this page.

2. Unzip the file to a location on your machine.

3. Run Android Studio.

4. Go to File > Open.... Navigate to the solution folder and click Open.

   On Windows: If you are in the Welcome to Android Studio dialog, click Open and navigate to the solution folder. Then click Open.

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

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

You can implement API key authentication or user authentication in this tutorial. Compare the differences below:

API key authentication

• Users are not required to sign in.
• Requires creating an API key credential with the correct privileges.
• API keys are long-lived access tokens.
• Service usage is billed to the API key owner/developer.
• Simplest authentication method to implement.
• Recommended approach for new ArcGIS developers.

Learn more in API key authentication.

User authentication

• Users are required to sign in with an ArcGIS account.
• User accounts must have privilege to access the ArcGIS services used in application.
• Requires creating OAuth credentials.
• Application uses a redirect URL and client ID.
• Service usage is billed to the organization of the user signed into the application.

Learn more in User authentication.

To learn more about the different types of authentication, visit Types of authentication.

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

1. Complete the Create an API key tutorial and create an API key with the following privilege(s):

   • Privileges
     • Location services > Basemaps

2. Copy and paste the API key access token into a safe location. It will be used in a later step.

Create new OAuth credentials to access the secure resources used in this tutorial.

1. Complete the Create OAuth credentials for user authentication tutorial to obtain a Client ID and Redirect URL.

   A Client ID uniquely identifies your app on the authenticating server. If the server cannot find an app with the provided Client ID, it will not proceed with authentication.

   The Redirect URL (also referred to as a callback url) is used to identify a response from the authenticating server when the system returns control back to your app after an OAuth login. Since it does not necessarily represent a valid endpoint that a user could navigate to, the redirect URL can use a custom scheme, such as my-app://auth. It is important to make sure the redirect URL used in your app's code matches a redirect URL configured on the authenticating server.

2. Copy and paste the Client ID and Redirect URL into a safe location. They will be used in a later step.

All users that access this application need account privileges to access the ArcGIS Basemap Styles service.

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.

1. In the Android view of Android Studio, open app > kotlin+java > com.example.app > MainActivity. Set the AuthenticationMode to .API_KEY.

   MainActivity.kt

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   class MainActivity : ComponentActivity() {
   
       private enum class AuthenticationMode { API_KEY, USER_AUTH }
   
       private val authenticationMode = AuthenticationMode.API_KEY
   

2. Set the apiKey property with your API key access token.

   MainActivity.kt

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       override fun onCreate(savedInstanceState: Bundle?) {
           super.onCreate(savedInstanceState)
   
           when (authenticationMode) {
               AuthenticationMode.API_KEY -> {
   
                   ArcGISEnvironment.apiKey = ApiKey.create("YOUR_ACCESS_TOKEN")
   
               }
   

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.

1. In the Android view of Android Studio, open app > kotlin+java > com.example.app > MainActivity. Set the AuthenticationMode to .USER_AUTH.

   MainActivity.kt

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   class MainActivity : ComponentActivity() {
       private enum class AuthenticationMode { API_KEY, USER_AUTH }
   
       private val authenticationMode = AuthenticationMode.USER_AUTH

2. Set your clientID and redirectURL values. You must use the RedirectURL that you supplied for your app in the user authentication part of the Set up authentication step.

   MainActivity.kt

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               AuthenticationMode.USER_AUTH -> {
                   authenticatorState.oAuthUserConfigurations = listOf(
                       OAuthUserConfiguration(
                           portalUrl = "https://www.arcgis.com",
   
                           clientId = "YOUR_CLIENT_ID",
                           redirectUrl = "YOUR_REDIRECT_URL"
   
                       )
                   )
   

3. Open app > manifests > AndroidManifest.xml.

4. Set the android:scheme and android:host using the scheme and host from your RedirectURL.

   A redirectURL is composed of a scheme and a host component. The format for the redirect url is scheme://host. For example, if the redirect url is myscheme://myhost then the scheme is myscheme and the host is myhost.

   AndroidManifest.xml

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                   <data
                       android:scheme="your_redirect_url_scheme"
                       android:host="your_redirect_url_host" />
   

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

Click Run > Run > app to run the app.

You should see point features (representing trailheads) draw on the map for an area in the Santa Monica Mountains in southern California.

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

• Add a point, line, and polygon
• Display a web map
• Display a scene
• Search for an address

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