TrackViewModel

AMD: require(["esri/widgets/Track/TrackViewModel"], (TrackVM) => { /* code goes here */ });
ESM: import TrackVM from "@arcgis/core/widgets/Track/TrackViewModel.js";
Class: esri/widgets/Track/TrackViewModel
Inheritance: TrackViewModel Accessor
Since: ArcGIS Maps SDK for JavaScript 4.0

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.
Show inherited properties Hide inherited properties
Name Type Summary Class

The name of the class.

Accessor
GeolocationPositionError|Error

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

TrackViewModel

An object used for setting optional position parameters.

TrackViewModel

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

TrackViewModel

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

TrackViewModel

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

TrackViewModel

A function that is used as an expression to evaluate geolocation points, and returns a boolean value.

TrackViewModel

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

The current state of the widget.

TrackViewModel

Indicates whether new positions are being watched.

TrackViewModel

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
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.

Possible Values:"disabled" |"ready" |"tracking" |"waiting" |"error"

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

Show inherited methods Hide inherited methods
Name Return Type Summary Class

Adds one or more handles which are to be tied to the lifecycle of the object.

Accessor

Emits an event on the instance.

TrackViewModel

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

TrackViewModel

Returns true if a named group of handles exist.

Accessor

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

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.

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