Add a feature layer from a portal item

Learn how to use an ArcGIS portal item to access and display a feature layer in a map.

You can host a variety of geographic data and other resources using ArcGIS Online. These portal items can also define how the data is presented. A web map or web scene, for example, not only defines the layers for a map or scene, but also how layers are symbolized, the minimum and/or maximum scales at which they display, and several other properties. Likewise, a hosted feature layer contains the data for the layer and also defines the symbols and other display properties for how it is presented. When you add a map, scene, or layer from a portal item to your ArcGIS Runtime app, everything that has been saved with the item is applied in your app. Adding portal items to your ArcGIS Runtime app rather than creating them programmatically saves you from writing a lot of code, and can provide consistency across apps that use the same data.

In this tutorial, you will add a hosted feature layer to display trailheads in the Santa Monica Mountains of Southern California. The hosted layer defines the trailhead locations (points) as well as the symbols used to display them.

Prerequisites

Before starting this tutorial:

You need an ArcGIS Location Platform or ArcGIS Online account.
Confirm that your system meets the system requirements.
An IDE for Android development in Kotlin.

Steps

Open an Android Studio project with Gradle

To start this tutorial, complete the Display a map tutorial. Or download and unzip the Display a map solution in a new folder.
Modify the old project for use in this new tutorial. Expand More info for instructions.
1. On your file system, delete the .idea folder, if present, at the top level of your project.
2. In the Android tool window, open app > res > values > strings.xml.
  
  In the <string name="app_name"> element, change the text content to Add a feature layer from a portal item.
  strings.xml
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  1 2 3 4 5 <resources> <string name="app_name">Add a feature layer from a portal item</string> </resources>
3. In the Android tool window, open Gradle Scripts > settings.gradle.
  
  Change the value of rootProject.name to "Add a feature layer from a portal item".
  settings.gradle
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  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 rootProject.name = "Add a feature layer from a portal item" include ':app'
4. Click File > Sync Project with Gradle files. Android Studio will recognize your changes and create a new .idea folder.
If you downloaded the solution, get an access token and set the API key.
1. Go to the Create an API key tutorial to obtain a new API key access token. 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 Android Studio: in the Android tool window, open app > java > com.example.app > MainActivity.
3. In the setApiKeyForApp() method, find the ArcGISRuntimeEnvironment.setApiKey("YOUR_ACCESS_TOKEN") call and paste your access token inside the double quotes, replacing YOUR_ACCESS_TOKEN.
  MainActivity.kt
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  Warning
  The access token is stored directly in the code as a convenience for this tutorial. Storing access tokens in the source code is not best practice.

Prepare files before coding the app

Modify the files from the Display a map tutorial so they can be used in this tutorial: you will add imports and remove code that we will not need.

In the Project tool window, make sure that the Android view is displayed. Open app/java/com.example.app, and click MainActivity.kt. Add the following imports, replacing those from the Display a map tutorial.

MainActivity.kt
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package com.example.app

import android.os.Bundle
import android.util.Log
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity

import com.esri.arcgisruntime.ArcGISRuntimeEnvironment
import com.esri.arcgisruntime.layers.FeatureLayer
import com.esri.arcgisruntime.loadable.LoadStatus
import com.esri.arcgisruntime.mapping.ArcGISMap
import com.esri.arcgisruntime.mapping.BasemapStyle
import com.esri.arcgisruntime.mapping.Viewpoint
import com.esri.arcgisruntime.mapping.view.MapView
import com.esri.arcgisruntime.portal.Portal
import com.esri.arcgisruntime.portal.PortalItem

import com.example.app.databinding.ActivityMainBinding

class MainActivity : AppCompatActivity() {

Delete the code for creating an ArcGISMap and setting the map on the map view. In the next section, we will code these steps in a different way, using a Kotlin scope function.

The only code left in setupMap at this point should be the line that sets the view point.

MainActivity.kt
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    // set up your map here. You will call this method from onCreate()
    private fun setupMap() {

        // create a map with the BasemapStyle streets
        val map = ArcGISMap(BasemapStyle.ARCGIS_TOPOGRAPHIC)

        // set the map to be displayed in the layout's MapView
        mapView.map = map

        // set the viewpoint, Viewpoint(latitude, longitude, scale)
        mapView.setViewpoint(Viewpoint(34.0270, -118.8050, 72000.0))

    }

Create a companion object containing the private read-only value named TAG, which will be used by the Toast when displaying any portal item loading error.

MainActivity.kt
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class MainActivity : AppCompatActivity() {

    companion object {
        private val TAG: String = MainActivity::class.java.simpleName
    }

    private val activityMainBinding by lazy {
      ActivityMainBinding.inflate(layoutInflater)
    }

    private val mapView: MapView by lazy {
      activityMainBinding.mapView
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        setContentView(activityMainBinding.root)
        setApiKeyForApp()
        setupMap()
    }

Display the ArcGIS portal item

You can reference an item (such as a web map or feature layer) hosted in a portal (such as ArcGIS Online) using its unique item ID. You will reference the Trailheads Styled feature layer stored in ArcGIS Online using its item ID: 2e4b3df6ba4b44969a3bc9827de746b3. You will then add that feature layer to your map's collection of data layers (operational layers).

In the setupMap() function, directly before the mapView.setViewpoint() call, do the following: create a PortalItem object that references the portal item that the feature layer will use. To do this, provide the item ID and an Portal object.

MainActivity.kt
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    // set up your map here. You will call this method from onCreate()
    private fun setupMap() {

        val portalItemId = "2e4b3df6ba4b44969a3bc9827de746b3"
        val portal = Portal("https://www.arcgis.com")
        val portalItem = PortalItem(portal, portalItemId)

        mapView.setViewpoint(Viewpoint(34.0270, -118.8050, 72000.0))

    }

Create a FeatureLayer passing the PortalItem and a layer ID of 0. Since the layerId parameter to the FeatureLayer constructor is a long, you can use the Kotlin function toLong() to convert the layer ID integer to a Long. Using a PortalItem to create a FeatureLayer causes the portal item to be loaded asynchronously.

A layer ID is required because a portal item may have more than one layer. For instance, when a feature service has 3 layers, such as trailheads (points), trails (polylines) and trail areas (polygons), the corresponding portal item would contain all three layers.

MainActivity.kt
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    private fun setupMap() {

        val portalItemId = "2e4b3df6ba4b44969a3bc9827de746b3"
        val portal = Portal("https://www.arcgis.com")
        val portalItem = PortalItem(portal, portalItemId)

        val layerId = 0
        val layer = FeatureLayer(portalItem, layerId.toLong())

        mapView.setViewpoint(Viewpoint(34.0270, -118.8050, 72000.0))

    }
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Create a ArcGISMap with a BasemapStyle named ARCGIS_TOPOGRAPHIC. Next, configure the map using the Kotlin scope function apply(). In the lambda that you pass to apply(), get the map's operational layers collection and add the layer to the collection.

MainActivity.kt
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    private fun setupMap() {

        val portalItemId = "2e4b3df6ba4b44969a3bc9827de746b3"
        val portal = Portal("https://www.arcgis.com")
        val portalItem = PortalItem(portal, portalItemId)

        val layerId = 0
        val layer = FeatureLayer(portalItem, layerId.toLong())

        mapView.map = ArcGISMap(BasemapStyle.ARCGIS_TOPOGRAPHIC).apply {
            operationalLayers.add(layer)
        }

        mapView.setViewpoint(Viewpoint(34.0270, -118.8050, 72000.0))

    }
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Leave the mapView.setViewpoint() line unchanged (in blue highlight below).

MainActivity.kt
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    // set up your map here. You will call this method from onCreate()
    private fun setupMap() {

        val portalItemId = "2e4b3df6ba4b44969a3bc9827de746b3"
        val portal = Portal("https://www.arcgis.com")
        val portalItem = PortalItem(portal, portalItemId)

        val layerId = 0
        val layer = FeatureLayer(portalItem, layerId.toLong())

        mapView.map = ArcGISMap(BasemapStyle.ARCGIS_TOPOGRAPHIC).apply {
            operationalLayers.add(layer)
        }

        mapView.setViewpoint(Viewpoint(34.0270, -118.8050, 72000.0))

    }
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Add a done loading listener to the portal item. In the lambda, check if the portal item is not loaded and, in that case, display a Toast with the loading error.

MainActivity.kt
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    private fun setupMap() {

        val portalItemId = "2e4b3df6ba4b44969a3bc9827de746b3"
        val portal = Portal("https://www.arcgis.com")
        val portalItem = PortalItem(portal, portalItemId)

        val layerId = 0
        val layer = FeatureLayer(portalItem, layerId.toLong())

        mapView.map = ArcGISMap(BasemapStyle.ARCGIS_TOPOGRAPHIC).apply {
            operationalLayers.add(layer)
        }

        mapView.setViewpoint(Viewpoint(34.0270, -118.8050, 72000.0))

        portalItem.addDoneLoadingListener {
            if (portalItem.loadStatus != LoadStatus.LOADED) {
                val error = "Failed to load portal item ${portalItem.loadError.message}"
                Log.e(TAG, error)
                Toast.makeText(this, error, Toast.LENGTH_LONG).show()
                return@addDoneLoadingListener
            }
        }

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

The Android Emulator should display and run your app in the Android Virtual Devcie (AVD) selected in the Android Studio toolbar:

Currently selected AVD in Android Studio

If your app builds but no AVD displays, you need to add one. Click Tools > AVD Manager > Create Virtual Device...

You should see a map of trail heads in the Santa Monica mountains. Click, drag, and scroll the mouse wheel on 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: