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 app, everything that has been saved with the item is applied in your app. Adding portal items to your 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

Steps

Open an Android Studio project with Gradle

1. To start this tutorial, complete the Display a map tutorial. Or download and unzip the Display a map solution in a new folder.

2. Modify the old project for use in this new tutorial. Expand More info for instructions.

   More info

   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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      <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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      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.

3. If you downloaded the Display a map solution project, get your API key and set it in your app.

   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 Android Studio: in the Android tool window, open app > java > com.example.app > MainActivity.

   3. In the setApiKey() function, find the ApiKey.create() call and paste your API key inside the quotes, replacing YOUR_API_KEY.

      MainActivity.kt

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          private fun setApiKey() {
              // It is not best practice to store API keys in source code. We have you insert one here
              // to streamline this tutorial.
      
              ArcGISEnvironment.apiKey = ApiKey.create("YOUR_API_KEY")
      
          }
      

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.

1. 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.

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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 androidx.databinding.DataBindingUtil
   import androidx.lifecycle.lifecycleScope
   import kotlinx.coroutines.launch
   import com.arcgismaps.ApiKey
   import com.arcgismaps.ArcGISEnvironment
   import com.arcgismaps.mapping.ArcGISMap
   import com.arcgismaps.mapping.BasemapStyle
   import com.arcgismaps.mapping.Viewpoint
   import com.arcgismaps.mapping.layers.FeatureLayer
   import com.arcgismaps.mapping.view.MapView
   import com.arcgismaps.portal.Portal
   import com.arcgismaps.mapping.PortalItem
   import com.example.app.databinding.ActivityMainBinding
   
   class MainActivity : AppCompatActivity() {
   

2. In the setupMap() function, delete the line that sets the view point. We will set the view point in a later step, when we load the portal item.

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       private fun setupMap() {
   
           val map = ArcGISMap(BasemapStyle.ArcGISTopographic)
   
           // set the map to be displayed in the layout's MapView
           mapView.map = map
   
           mapView.setViewpoint(Viewpoint(34.0270, -118.8050, 72000.0))
   
       }
   

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).

1. In the setupMap() function, add the following: create a PortalItem object referencing the portal item that the feature layer will use. To do this, provide the item ID and an Portal object.

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       private fun setupMap() {
   
           val map = ArcGISMap(BasemapStyle.ArcGISTopographic)
   
           // set the map to be displayed in the layout's MapView
           mapView.map = map
   
           val portalItem = PortalItem(
               Portal("https://www.arcgis.com"),
               itemId = "2e4b3df6ba4b44969a3bc9827de746b3"
           )
   
       }
   

2. Load the portal item.The PortalItem class implements the Loadable interface, which declares the suspend function load(). As a suspend function, it must be called in a coroutine scope; we create one here with lifecycleScope.launch().

   The load() function returns a Result<Unit>, on which you should call .onSuccess and pass a lambda. In the lambda, create a FeatureLayer with the PortalItem and a layer ID of 0.

   Why is a layer ID required?

   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 map = ArcGISMap(BasemapStyle.ArcGISTopographic)
   
           // set the map to be displayed in the layout's MapView
           mapView.map = map
   
           val portalItem = PortalItem(
               Portal("https://www.arcgis.com"),
               itemId = "2e4b3df6ba4b44969a3bc9827de746b3"
           )
   
           lifecycleScope.launch {
               portalItem.load().onSuccess {
                   val featureLayer = FeatureLayer.createWithItem(portalItem)
   
           }
   
       }
   

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3. Add the feature layer to the map.

   MainActivity.kt

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           lifecycleScope.launch {
               portalItem.load().onSuccess {
                   val featureLayer = FeatureLayer.createWithItem(portalItem)
   
                   mapView.map?.operationalLayers?.add(featureLayer)
   
           }
   

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4. Set the view point on the map view. Use the same view point settings as in the Display a map tutorial.

   MainActivity.kt

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           lifecycleScope.launch {
               portalItem.load().onSuccess {
                   val featureLayer = FeatureLayer.createWithItem(portalItem)
   
                   mapView.map?.operationalLayers?.add(featureLayer)
   
                   mapView.setViewpoint(Viewpoint(34.0270, -118.8050, 72000.0))
   
           }
   

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5. In the .onFailure lambda, handle the case where the portal item failed to load.

   MainActivity.kt

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           lifecycleScope.launch {
               portalItem.load().onSuccess {
                   val featureLayer = FeatureLayer.createWithItem(portalItem)
   
                   mapView.map?.operationalLayers?.add(featureLayer)
   
                   mapView.setViewpoint(Viewpoint(34.0270, -118.8050, 72000.0))
   
               }.onFailure { error ->
                   showError("Failed to load portal item. " + error.message.toString())
               }
   
           }
   

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Click Run > Run > app to run the app.

You should see a map of trail heads in the Santa Monica mountains. Double tap, Drag, pinch in, and pinch out 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:

• Display a web map
• Display a web scene