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
The following are required for this tutorial:
- An ArcGIS account to access API keys. If you don't have an account, sign up for free.
- A development and deployment environment that meets the system requirements.
- An IDE for Android development in Kotlin.
Steps
Open an Android Studio project with Gradle
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To start this tutorial, complete the Display a map tutorial. Or download and unzip the Display a map solution in a new folder.
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Modify the old project for use in this new tutorial. Expand More info for instructions.
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On your file system, delete the .idea folder, if present, at the top level of your project.
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In the Android tool window, open app > res > values > strings.xml.
In the
<string name="app_
element, change the text content to Add a feature layer from a portal item.name"> strings.xmlUse dark colors for code blocks Change line <resources> <string name="app_name">Add a feature layer from a portal item</string> </resources>
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In the Android tool window, open Gradle Scripts > settings.gradle.
Change the value of
root
to "Add a feature layer from a portal item".Project.name settings.gradleUse dark colors for code blocks Change line rootProject.name = "Add a feature layer from a portal item" include ':app'
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Click File > Sync Project with Gradle files. Android Studio will recognize your changes and create a new .idea folder.
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If you downloaded the
Display a map
solution project, get your API key and set it in your app.An API Key enables access to services, web maps, and web scenes hosted in ArcGIS Online.
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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.
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In Android Studio: in the Android tool window, open app > java > com.example.app > MainActivity.
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In the
set
function, find theA p i Key() ApiKey.create()
call and paste your API key inside the quotes, replacing YOUR_API_KEY.MainActivity.ktUse dark colors for code blocks 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") }
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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.
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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.ktUse dark colors for code blocks 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() {
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In the
setup
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.Map() MainActivity.ktUse dark colors for code blocks 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).
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In the
setup
function, add the following: create aMap() PortalItem
object referencing the portal item that the feature layer will use. To do this, provide the item ID and anPortal
object.MainActivity.ktUse dark colors for code blocks 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" ) }
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Load the portal item.The
PortalItem
class implements theLoadable
interface, which declares the suspend functionload()
. As a suspend function, it must be called in a coroutine scope; we create one here withlifecycle
.Scope.launch() The
load()
function returns aResult<
, on which you should callUnit> .on
and pass a lambda. In the lambda, create aSuccess FeatureLayer
with thePortalItem
and a layer ID of 0.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.ktUse dark colors for code blocks Add line. Add line. Add line. Add line. Add line. 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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Add the feature layer to the map.
MainActivity.ktUse dark colors for code blocks Add line. lifecycleScope.launch { portalItem.load().onSuccess { val featureLayer = FeatureLayer.createWithItem(portalItem) mapView.map?.operationalLayers?.add(featureLayer) }
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Set the view point on the map view. Use the same view point settings as in the Display a map tutorial.
MainActivity.ktUse dark colors for code blocks Add line. 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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In the
.on
lambda, handle the case where the portal item failed to load.Failure MainActivity.ktUse dark colors for code blocks Add line. Add line. Add line. 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()) } }
Click Run > Run > app to run the app.
In Android Studio, you have two choices for running your app: an actual Android device or the Android Emulator.
Android device
Connect your computer to your Android device, using USB or Wi-Fi. For more details, see How to connect your Android device.
Android Emulator
Create an AVD (Android Virtual Device) to run in the Android Emulator. For details, see Run apps on the Android Emulator.
Selecting a device
When you build and run an app in Android Studio, you must first select a device. From the Android Studio toolbar, you can access the drop-down list of your currently available devices, both virtual and physical.
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If you cannot access the list on the toolbar, click Tools > Device Manager.
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: