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.

add a feature layer from a portal item

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

The following are required for this tutorial:

  1. An ArcGIS account to access API keys. If you don't have an account, sign up for free.
  2. A development and deployment environment that meets the system requirements.
  3. An IDE for Android development in Kotlin.

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.

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

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.

    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 androidx.databinding.DataBindingUtil
    import androidx.lifecycle.lifecycleScope
    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
    import kotlinx.coroutines.launch
    
    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.

    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
    
            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.

    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)
    
            }
    
        }
    
    Expand
  3. Add the feature layer to the map.

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            lifecycleScope.launch {
                portalItem.load().onSuccess {
                    val featureLayer = FeatureLayer.createWithItem(portalItem)
    
                    mapView.map?.operationalLayers?.add(featureLayer)
    
            }
    
    Expand
  4. Set the view point on the map view. Use the same view point settings as in the Display a map tutorial.

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

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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())
                }
    
            }
    
    Expand

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:

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