TrackViewModel | API Reference | ArcGIS Maps SDK for JavaScript 4.31

Provides the logic for the Track widget, which animates the View to the user's location when clicked and tracks it as the location is updated.

The Track widget is only available in secure contexts, such as HTTPS. Note that localhost is considered "potentially secure" and can be used for easy testing in browsers that support Window.isSecureContext.

For additional information regarding this, visit the ArcGIS blog, Increased web API security in Google Chrome.

See also

Example

let trackWidget = new Track({
  viewModel: {    // autocasts as new TrackViewModel()
    view: view,   // attaches the Track to the view
  }
};

Constructors

TrackViewModel Constructor new TrackViewModel(properties)

Parameter

properties Object

optional

See the properties for a list of all the properties that may be passed into the constructor.

Property Overview

Any properties can be set, retrieved or listened to. See the Working with Properties topic.

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Type	Summary	Class
String	The name of the class.	Accessor
GeolocationPositionError\|Error	Error that caused the last track-error event to fire.	TrackViewModel
Object	An object used for setting optional position parameters.	TrackViewModel
Boolean	Indicates whether to navigate the view to the position and scale of the geolocated result.	TrackViewModel
GoToOverride	This function provides the ability to override either the MapView goTo() or SceneView goTo() methods.	TrackViewModel
Graphic	The graphic used to show the user's location on the map.	TrackViewModel
Function	A function that is used as an expression to evaluate geolocation points, and returns a boolean value.	TrackViewModel
Number	Indicates the scale to set on the view when navigating to the position of the geolocated result, after a location is returned from the track event.	TrackViewModel
String	The current state of the widget.	TrackViewModel
Boolean	Indicates whether new positions are being watched.	TrackViewModel
MapView\|SceneView	The view associated with the widget.	TrackViewModel

Property Details

declaredClass Inherited Property declaredClass Stringreadonly Inherited from Accessor Since: ArcGIS Maps SDK for JavaScript 4.7 Accessor since 4.0, declaredClass added at 4.7.

The name of the class. The declared class name is formatted as esri.folder.className.

error Property error GeolocationPositionError |Error Since: ArcGIS Maps SDK for JavaScript 4.29 TrackViewModel since 4.0, error added at 4.29.

Error that caused the last track-error event to fire.

Default Value:null

Example

if(track.viewModel.state === 'error')
  console.error(track.viewModel.error);

geolocationOptions Property geolocationOptions Object

An object used for setting optional position parameters. Refer to the Geolocation API Specification for details on using these parameters.

Default Value:null

Example

const track = new Track({
  view: view,
  // Set optional position parameters
  geolocationOptions: {
    maximumAge: 0,
    timeout: 15000,
    enableHighAccuracy: true
  }
});

goToLocationEnabled Property goToLocationEnabled Boolean

Indicates whether to navigate the view to the position and scale of the geolocated result.

Default Value:true

goToOverride Property goToOverride GoToOverride Since: ArcGIS Maps SDK for JavaScript 4.8 TrackViewModel since 4.0, goToOverride added at 4.8.

This function provides the ability to override either the MapView goTo() or SceneView goTo() methods.

See also

esri/views/MapView#goTo
SceneView

Example

// The following snippet uses the Search widget but can be applied to any
// widgets that support the goToOverride property.
search.goToOverride = function(view, goToParams) {
  goToParams.options = {
    duration: updatedDuration
  };
  return view.goTo(goToParams.target, goToParams.options);
};

graphic Property graphic Graphic

The graphic used to show the user's location on the map.

Example

const trackWidget = new Track({
  // Assign the track widget to a view
  view: view,
  // Overwrite the default symbol used for the
  // graphic placed at the location of the user
  graphic: new Graphic ({
   symbol: {
     // autocasts as new SimpleMarkerSymbol()
     type: "simple-marker",
     size: "12px",
     color: "blue",
     // autocasts as new SimpleLineSymbol()
     outline: {
       color: "#efefef",
       width: "1.5px"
     }
   }
 })
});

positionFilterFunction Property positionFilterFunction Function Since: ArcGIS Maps SDK for JavaScript 4.27 TrackViewModel since 4.0, positionFilterFunction added at 4.27.

A function that is used as an expression to evaluate geolocation points, and returns a boolean value. If the function returns true, the widget will draw a graphic and navigate to the position. The widget will ignore false values and not draw a graphic and not navigate to the position.

Example use cases include smoothing out geolocation anomalies and geofencing.

Default Value:null

Example

// Exclude locations that full outside an extent.
track.viewModel.positionFilterFunction = (value) => {
  const { longitude, latitude } = value.position.coords;
  const myLocation = new Point({ longitude, latitude });
  const geofenceExtent = new Extent({
    // whatever
  });
  return geometryEngine.within(myLocation, geofenceExtent);
};

scale Property scale Number Since: ArcGIS Maps SDK for JavaScript 4.7 TrackViewModel since 4.0, scale added at 4.7.

Indicates the scale to set on the view when navigating to the position of the geolocated result, after a location is returned from the track event.

By default, the view will navigate to a scale of 2500 for 3D and 4514 for 2D. To override the default in 2D, set the scale property and also set snapToZoom to false. For 2D views the value should be within the effectiveMinScale and effectiveMaxScale.

Default Value:null

state Property state Stringreadonly

The current state of the widget.

Default Value:"disabled"

tracking Property tracking Booleanreadonly

Indicates whether new positions are being watched.

Default Value:false

view Property view MapView |SceneView

The view associated with the widget.

Method Overview

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Return Type	Summary	Class
	Adds one or more handles which are to be tied to the lifecycle of the object.	Accessor
Boolean	Emits an event on the instance.	TrackViewModel
Boolean	Indicates whether there is an event listener on the instance that matches the provided event name.	TrackViewModel
Boolean	Returns true if a named group of handles exist.	Accessor
Object	Registers an event handler on the instance.	TrackViewModel
	Removes a group of handles owned by the object.	Accessor
	When executed, tracking starts at the user's location.	TrackViewModel
	Stops tracking the user's location when executed.	TrackViewModel

Method Details

addHandles Inherited Method addHandles(handleOrHandles, groupKey) Inherited from Accessor Since: ArcGIS Maps SDK for JavaScript 4.25 Accessor since 4.0, addHandles added at 4.25.

Adds one or more handles which are to be tied to the lifecycle of the object. The handles will be removed when the object is destroyed.

// Manually manage handles
const handle = reactiveUtils.when(
  () => !view.updating,
  () => {
    wkidSelect.disabled = false;
  },
  { once: true }
);

this.addHandles(handle);

// Destroy the object
this.destroy();

Parameters

handleOrHandles WatchHandle|WatchHandle []

Handles marked for removal once the object is destroyed.

groupKey *

optional

Key identifying the group to which the handles should be added. All the handles in the group can later be removed with Accessor.removeHandles(). If no key is provided the handles are added to a default group.

emit Method emit(type, event){Boolean} Since: ArcGIS Maps SDK for JavaScript 4.5 TrackViewModel since 4.0, emit added at 4.5.

Emits an event on the instance. This method should only be used when creating subclasses of this class.

Parameters

type String

The name of the event.

event Object

optional

The event payload.

Returns

Type	Description
Boolean	`true` if a listener was notified

hasEventListener Method hasEventListener(type){Boolean}

Indicates whether there is an event listener on the instance that matches the provided event name.

Parameter

type String

The name of the event.

Returns

Type	Description
Boolean	Returns true if the class supports the input event.

hasHandles Inherited Method hasHandles(groupKey){Boolean} Inherited from Accessor Since: ArcGIS Maps SDK for JavaScript 4.25 Accessor since 4.0, hasHandles added at 4.25.

Returns true if a named group of handles exist.

Parameter

groupKey *

optional

A group key.

Returns

Type	Description
Boolean	Returns `true` if a named group of handles exist.

Example

// Remove a named group of handles if they exist.
if (obj.hasHandles("watch-view-updates")) {
  obj.removeHandles("watch-view-updates");
}

on Method on(type, listener){Object}

Registers an event handler on the instance. Call this method to hook an event with a listener.

Parameters

type String|String []

An event or an array of events to listen for.

listener Function

The function to call when the event fires.

Returns

Type Description

Object

Returns an event handler with a remove() method that should be called to stop listening for the event(s).

Property	Type	Description
remove	Function	When called, removes the listener from the event.

Example

view.on("click", function(event){
  // event is the event handle returned after the event fires.
  console.log(event.mapPoint);
});

removeHandles Inherited Method removeHandles(groupKey) Inherited from Accessor Since: ArcGIS Maps SDK for JavaScript 4.25 Accessor since 4.0, removeHandles added at 4.25.

Removes a group of handles owned by the object.

Parameter

groupKey *

optional

A group key or an array or collection of group keys to remove.

Example

obj.removeHandles(); // removes handles from default group

obj.removeHandles("handle-group");
obj.removeHandles("other-handle-group");

start Method start()

When executed, tracking starts at the user's location.

stop Method stop()

Stops tracking the user's location when executed.

Event Overview

Name	Type	Summary	Class
	{position: Object}	Fires after the start() method is called and a position is found.	TrackViewModel
	{error: GeolocationPositionError\|Error}	Fires after the start() method is called and an error is returned.	TrackViewModel

Event Details

track Event track

Fires after the start() method is called and a position is found.

Property: position Object

Position returned from the Geolocation API.

track-error Event track-error

Fires after the start() method is called and an error is returned.

Property: error GeolocationPositionError|Error

The Error object returned if an error occurred while tracking.