Display device location

Learn how to display the current device location on a map or scene.

You can display the device location on a map or scene. This is important for workflows that require the user's current location, such as finding nearby businesses, navigating from the current location, or identifying and collecting geospatial information.

By default, location display uses the device's location provider. Your app can also process input from other location providers, such as an external GPS receiver or a provider that returns a simulated location. For more information, see the Show device location topic.

Prerequisites

Before starting this tutorial:

You need an ArcGIS Location Platform or ArcGIS Online account.
Confirm that your system meets the minimum system requirements.
An IDE for Java.

Steps

Open a Java project with Gradle

To start this tutorial, complete the Display a map tutorial, or download and unzip the Display a map solution into a new folder.
Open the build.gradle file as a project in IntelliJ IDEA.
If you downloaded the solution, get an access token and set the API key.
An API Key gives your app access to secure resources used in this tutorial.
1. Go to the Create an API key tutorial to obtain a new API key access token using your ArcGIS Location Platform or ArcGIS Online account. 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 IntelliJ IDEA's Project tool window, open src/main/java/com.example.app and double-click App.
3. In the start() method, set the API key property on the ArcGISRuntimeEnvironment with your access token. Replace YOUR_ACCESS_TOKEN with your copied access token. Be sure to surround your access token with double quotes as it is a string.
  App.java
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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, change the application title, and remove unnecessary code; you will then add a requirement to the Java module definition and a dependency to the build configuration.

In IntelliJ IDEA's Project tool window, open src/main/java/com.example.app and double-click App. Add the following imports, replacing those from the Display a map tutorial

App.java
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package com.example.app;

import java.nio.charset.StandardCharsets;
import java.util.Calendar;

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Alert;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

import com.esri.arcgisruntime.ArcGISRuntimeEnvironment;
import com.esri.arcgisruntime.geometry.Geometry;
import com.esri.arcgisruntime.geometry.Polyline;
import com.esri.arcgisruntime.geometry.SpatialReferences;
import com.esri.arcgisruntime.loadable.LoadStatus;
import com.esri.arcgisruntime.location.SimulatedLocationDataSource;
import com.esri.arcgisruntime.location.SimulationParameters;
import com.esri.arcgisruntime.mapping.ArcGISMap;
import com.esri.arcgisruntime.mapping.BasemapStyle;
import com.esri.arcgisruntime.mapping.view.LocationDisplay;
import com.esri.arcgisruntime.mapping.view.MapView;

import org.apache.commons.io.IOUtils;


public class App extends Application {

In the start() life-cycle method, change the title that will appear on the application window to Display device location.

App.java
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  @Override
  public void start(Stage stage) {

    try {

      // set the title and size of the stage and show it
      stage.setTitle("Display device location");

      stage.setWidth(800);
      stage.setHeight(700);
      stage.show();

Delete the map's initial viewpoint. The map will zoom to the extent of the current location, so this code is no longer needed.

App.java
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    // create a map view to display the map and add it to the stack pane
    mapView = new MapView();
    stackPane.getChildren().add(mapView);

    ArcGISMap map = new ArcGISMap(BasemapStyle.ARCGIS_TOPOGRAPHIC);

    // set the map on the map view
    mapView.setMap(map);

    mapView.setViewpoint(new Viewpoint(34.02700, -118.80543, 144447.638572));

In IntelliJ IDEA's Project tool window, double-click module-info.java. Add one requires module directive.

module-info.java
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Add line.module com.example.app {
  // require ArcGIS Runtime module
  requires com.esri.arcgisruntime;

  // requires JavaFX modules that the application uses
  requires javafx.graphics;

  // requires SLF4j module
  requires org.slf4j.nop;


  requires org.apache.commons.io;


  exports com.example.app;
}

In IntelliJ IDEA's Project tool window, double-click build.gradle. Add one dependency and load the gradle changes.

build.gradle
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Add line.dependencies {

    implementation 'commons-io:commons-io:2.17.0'

    implementation "com.esri.arcgisruntime:arcgis-java:$arcgisVersion"
    natives "com.esri.arcgisruntime:arcgis-java-jnilibs:$arcgisVersion"
    natives "com.esri.arcgisruntime:arcgis-java-resources:$arcgisVersion"
    implementation "org.slf4j:slf4j-nop:2.0.16"
}
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Create simulated location data

Simulation of location data allows this app to run on devices that do not have location services or do not have an actively updating GPS signal. Simulated data is also useful for testing your own location-enabled apps. For more information, see Simulated device location updates.

For this tutorial, you will use simulated location data: a set of location points defined in json. The location points are from a walk around a large parking lot. To display a user's real position, you would use NmeaLocationDataSource instead.

On your file system, create a file named polyline_data.json in the src/main/resources/ directory of your project. Then paste the following json code into it.

polyline_data.json
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{
  "paths": [
    [
      [-117.19810659418077, 34.057405229888325],
      [-117.19814377275544, 34.057211176001729],
      [-117.19775710911107, 34.057177293200773],
      [-117.1973868388223, 34.057255151357538],
      [-117.19724927620958, 34.057458446284997],
      [-117.1973853161779, 34.057553079922293],
      [-117.19752637683034, 34.057534135490592],
      [-117.19771293355865, 34.057471254533809],
      [-117.19794672280628, 34.057485315324428],
      [-117.19810659418077, 34.057405229888325]
    ]
  ],
  "spatialReference": {
    "wkid": 102100,
    "latestWkid": 3857
  }
}

From those location points, create a Polyline that traces the route through the parking lot.

In App.java, get the data from the json file, using IOUtils.string(), which you imported from the commons-io dependency in the previous section. Then call Geometry.fromJson() and cast the returned Geometry to a Polyline.

App.java
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      // access the json of the location points
      String polylineData = IOUtils.toString(getClass().getResourceAsStream(
              "/polyline_data.json"), StandardCharsets.UTF_8);

      // create a polyline from the location points
      Polyline locations = (Polyline) Geometry.fromJson(polylineData, SpatialReferences.getWgs84());

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Create a SimulatedLocationDataSource and set the location data points on it, and then pass the polyline describing the route and the SimulationParameters to SimulateLocationDataSource.setLocations().

App.java
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Add line.Add line.Add line.Add line.Add line.      // access the json of the location points
      String polylineData = IOUtils.toString(getClass().getResourceAsStream(
              "/polyline_data.json"), StandardCharsets.UTF_8);

      // create a polyline from the location points
      Polyline locations = (Polyline) Geometry.fromJson(polylineData, SpatialReferences.getWgs84());

      // create a simulated location data source
      SimulatedLocationDataSource simulatedLocationDataSource = new SimulatedLocationDataSource();
      // set the location of the simulated location data source with simulation parameters to set a consistent velocity
      simulatedLocationDataSource.setLocations(
              locations, new SimulationParameters(Calendar.getInstance(), 5.0, 0.0, 0.0));

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Show the current location

Each map view has its own instance of a LocationDisplay that shows the current location (point) of the device. This is displayed as an overlay in the map view.

Instances of this class manage the display of device location on a map view: the symbols, animation, auto pan behavior, and so on. Location display is an overlay of the map view, and displays above everything else, including graphics overlays.

The location display does not retrieve location information, that is the job of the associated data source, which provides location updates on a regular basis. In addition to the default system location data source, you can use location providers based on external GPS devices or a simulated location source.

Each map view has its own instance of a location display and instances of location display and location data source are not shared by multiple map views. This allows you to start and stop location display independently on multiple map views without affecting each other.

In start(), get the location display and set the simulated location data source on it.

App.java
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Add line.Add line.Add line.      // access the json of the location points
      String polylineData = IOUtils.toString(getClass().getResourceAsStream(
              "/polyline_data.json"), StandardCharsets.UTF_8);

      // create a polyline from the location points
      Polyline locations = (Polyline) Geometry.fromJson(polylineData, SpatialReferences.getWgs84());

      // create a simulated location data source
      SimulatedLocationDataSource simulatedLocationDataSource = new SimulatedLocationDataSource();
      // set the location of the simulated location data source with simulation parameters to set a consistent velocity
      simulatedLocationDataSource.setLocations(
              locations, new SimulationParameters(Calendar.getInstance(), 5.0, 0.0, 0.0));

      // configure the map view's location display to follow the simulated location data source
      LocationDisplay locationDisplay = mapView.getLocationDisplay();
      locationDisplay.setLocationDataSource(simulatedLocationDataSource);

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Set the autopan mode to recenter. (For other autopan modes, see the LocationDisplay.AutoPanMode enum.) Then set the initial zoom scale to 1000, using LocationDisplay.setInitialZoomScale().

App.java
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Add line.Add line.      // access the json of the location points
      String polylineData = IOUtils.toString(getClass().getResourceAsStream(
              "/polyline_data.json"), StandardCharsets.UTF_8);

      // create a polyline from the location points
      Polyline locations = (Polyline) Geometry.fromJson(polylineData, SpatialReferences.getWgs84());

      // create a simulated location data source
      SimulatedLocationDataSource simulatedLocationDataSource = new SimulatedLocationDataSource();
      // set the location of the simulated location data source with simulation parameters to set a consistent velocity
      simulatedLocationDataSource.setLocations(
              locations, new SimulationParameters(Calendar.getInstance(), 5.0, 0.0, 0.0));

      // configure the map view's location display to follow the simulated location data source
      LocationDisplay locationDisplay = mapView.getLocationDisplay();
      locationDisplay.setLocationDataSource(simulatedLocationDataSource);

      locationDisplay.setAutoPanMode(LocationDisplay.AutoPanMode.RECENTER);
      locationDisplay.setInitialZoomScale(1000);

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Once the map has loaded, start the location display.

App.java
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Add line.Add line.Add line.Add line.Add line.Add line.Add line.Add line.Add line.Add line.      // access the json of the location points
      String polylineData = IOUtils.toString(getClass().getResourceAsStream(
              "/polyline_data.json"), StandardCharsets.UTF_8);

      // create a polyline from the location points
      Polyline locations = (Polyline) Geometry.fromJson(polylineData, SpatialReferences.getWgs84());

      // create a simulated location data source
      SimulatedLocationDataSource simulatedLocationDataSource = new SimulatedLocationDataSource();
      // set the location of the simulated location data source with simulation parameters to set a consistent velocity
      simulatedLocationDataSource.setLocations(
              locations, new SimulationParameters(Calendar.getInstance(), 5.0, 0.0, 0.0));

      // configure the map view's location display to follow the simulated location data source
      LocationDisplay locationDisplay = mapView.getLocationDisplay();
      locationDisplay.setLocationDataSource(simulatedLocationDataSource);

      locationDisplay.setAutoPanMode(LocationDisplay.AutoPanMode.RECENTER);
      locationDisplay.setInitialZoomScale(1000);

      map.addDoneLoadingListener(() -> {
        if (map.getLoadStatus() == LoadStatus.LOADED) {

          // start the location display
          locationDisplay.startAsync();

        } else {
          new Alert(Alert.AlertType.ERROR, "Map failed to load: " + map.getLoadError().getCause().getMessage()).show();
        }
      });
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Wrap your code in start() with try and catch blocks.

App.java
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Add line.  @Override
  public void start(Stage stage) {

    try {

      // set the title and size of the stage and show it
      stage.setTitle("Display device location");

      stage.setWidth(800);
      stage.setHeight(700);
      stage.show();
Expand

Run the app. Ensure to run the app as a Gradle task and not as an application in your IDE. In the Gradle tool window, under Tasks > application, double-click run.

You will see the initial location displayed as a round blue symbol on the map. The location symbol then changes into a white arrowhead within a blue circle and begins walking around the parking lot as the location display consumes the simulated data. When the end of the data is reached, the route repeats.

Different location symbols are used in different autopan modes, and a location symbol's appearance changes whenever a location is acquired. See LocationDisplay.AutoPanMode for details.

By default, a round blue symbol is used to display the device's location. The location data source tries to get the most accurate location available but depending upon signal strength, satellite positions, and other factors, the location reported could be an approximation. A semi-transparent circle around the location symbol indicates the range of accuracy. As the device moves and location updates are received, the location symbol will be repositioned on the map.

What's next?

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