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StreamLayerView

Class: esri/views/layers/StreamLayerView
Inheritance: StreamLayerView LayerView Accessor
Since: ArcGIS API for JavaScript 4.4

Represents the LayerView of a StreamLayer after it has been added to a Map in either a MapView or SceneView.

The StreamLayerView is responsible for rendering a StreamLayer's features as graphics in the View. The methods in the StreamLayerView provide developers with the ability to query and highlight graphics in the view. See the code snippets in the methods below for examples of how to access client-side graphics from the view.

It connects to a server that emits geographic features continuously. The stream layer is suitable when you would like to map dynamic streams of data that are unbounded and continuous. When a StreamLayer is added to a map, users are able to see any real-time updates pushed out by the server. For more information, read the documentation of StreamLayer.

See also:

Property Overview

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

The error that explains an unsuccessful attempt to connect to the stream service or an unexpected disconnection from the stream service.

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more detailsStreamLayerView
String

The status of the Web Socket connection with the stream service.

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more detailsStreamLayerView
String

The name of the class.

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more detailsAccessor
FeatureEffect

The effect applied to the layer view.

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more detailsStreamLayerView
FeatureFilter

The attribute, geometry, and time extent filter.

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more detailsStreamLayerView
Layer

The layer being viewed.

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more detailsLayerView
Boolean

Value is true if the layer is suspended (i.e., layer will not redraw or update itself when the extent changes).

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more detailsLayerView
Boolean

Value is true when the layer is updating; for example, if it is in the process of fetching data.

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more detailsLayerView
Boolean

When true, the layer is visible in the view.

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more detailsLayerView

Property Details

connectionError Errorreadonly

The error that explains an unsuccessful attempt to connect to the stream service or an unexpected disconnection from the stream service.

connectionStatus Stringreadonly

The status of the Web Socket connection with the stream service. This property can be watched to see if the connection is lost unexpectedly.

Possible Values:"connected"|"disconnected"

declaredClass Stringreadonly inherited
Since: ArcGIS API for JavaScript 4.7

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

Since: ArcGIS API for JavaScript 4.15

The effect applied to the layer view. The effect allows for the selection of features via a filter, and an includedEffect and excludedEffect are applied to those features that respectively pass or fail the filter requirements.

Known Limitations

FeatureEffect is not supported in 3D SceneViews.

See also:
Example:
// set effect on excluded features (if outside of the geometry)
// make them gray and transparent
streamLayerView.effect = {
  filter: { // autocasts to FeatureFilter
    geometry: areaOfInterest,
  },
  excludedEffect: "grayscale(100%) opacity(30%)"
}
Since: ArcGIS API for JavaScript 4.11

The attribute, geometry, and time extent filter. Only the features that satisfy the filter are displayed on the view.

See also:
layer Layerreadonly inherited

The layer being viewed.

suspended Booleanreadonly inherited

Value is true if the layer is suspended (i.e., layer will not redraw or update itself when the extent changes).

updating Booleanreadonly inherited

Value is true when the layer is updating; for example, if it is in the process of fetching data.

Default Value:false

When true, the layer is visible in the view. Set this property to false to hide the layer from the view.

Default Value:true

Method Overview

NameReturn TypeSummaryClass
Boolean

Emits an event on the instance.

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more detailsStreamLayerView
Boolean

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

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more detailsStreamLayerView
Handle

Highlights the given feature(s).

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more detailsStreamLayerView
Boolean

isFulfilled() may be used to verify if creating an instance of the class is fulfilled (either resolved or rejected).

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more detailsLayerView
Boolean

isRejected() may be used to verify if creating an instance of the class is rejected.

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more detailsLayerView
Boolean

isResolved() may be used to verify if creating an instance of the class is resolved.

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more detailsLayerView
Object

Registers an event handler on the instance.

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more detailsStreamLayerView
Promise<Object>

Executes a Query against features available for drawing in the layer view and returns the Extent of features that satisfy the query.

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more detailsStreamLayerView
Promise<Number>

Executes a Query against features available for drawing in the layer view and returns the number of features that satisfy the query.

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more detailsStreamLayerView
Promise<FeatureSet>

Executes a Query against features available for drawing in the layer view and returns a FeatureSet.

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more detailsStreamLayerView
Promise<FeatureSet>

If a trackIdField is specified on the stream service, this method executes a Query against features available for drawing in the layer view and returns a FeatureSet of the latest observations for each trackId that satisfy the query.

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more detailsStreamLayerView
Promise<Number[]>

Executes a Query against features available for drawing in the layer view and returns array of the ObjectIDs of features that satisfy the input query.

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more detailsStreamLayerView
Promise

when() may be leveraged once an instance of the class is created.

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more detailsLayerView

Method Details

emit(type, event){Boolean}
Since: ArcGIS API for JavaScript 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:
TypeDescription
Booleantrue if a listener was notified
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:
TypeDescription
BooleanReturns true if the class supports the input event.
highlight(target){Handle}

Highlights the given feature(s).

Parameter:
optional

The feature(s) to highlight. When passing a graphic or array of graphics, each feature must have a valid objectID. You may alternatively pass one or more objectIDs as a single number or an array.

Returns:
TypeDescription
HandleReturns a highlight handler with a remove() method that can be called to remove the highlight.
See also:
Example:
// highlight feature on pointer-move
view.on("pointer-move", function(event){
  view.hitTest(event).then(function(response){
    if (response.results.length) {
      var graphic = response.results.filter(function (result) {
        return result.graphic.layer === myLayer;
      })[0].graphic;

     view.whenLayerView(graphic.layer).then(function(layerView){
       layerView.highlight(graphic);
     });
    }
  });
});
isFulfilled(){Boolean}inherited

isFulfilled() may be used to verify if creating an instance of the class is fulfilled (either resolved or rejected). If it is fulfilled, true will be returned.

Returns:
TypeDescription
BooleanIndicates whether creating an instance of the class has been fulfilled (either resolved or rejected).
isRejected(){Boolean}inherited

isRejected() may be used to verify if creating an instance of the class is rejected. If it is rejected, true will be returned.

Returns:
TypeDescription
BooleanIndicates whether creating an instance of the class has been rejected.
isResolved(){Boolean}inherited

isResolved() may be used to verify if creating an instance of the class is resolved. If it is resolved, true will be returned.

Returns:
TypeDescription
BooleanIndicates whether creating an instance of the class has been resolved.
on(type, listener){Object}

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

Parameters:

A event type, or an array of event types, to listen for.

listener Function

The function to call when the event is fired.

Returns:
TypeDescription
ObjectReturns an event handler with a remove() method that can be called to stop listening for the event(s).
PropertyTypeDescription
removeFunctionWhen 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);
});
queryExtent(query, options){Promise<Object>}
Since: ArcGIS API for JavaScript 4.9

Executes a Query against features available for drawing in the layer view and returns the Extent of features that satisfy the query. If query parameters are not provided, the extent and count of all features available for drawing are returned.

Known Limitations

  • Spatial queries have the same limitations as those listed in the projection engine documentation.
  • Spatial queries are not currently supported if the layer view has any of the following SpatialReferences:
    • GDM 2000 (4742) – Malaysia
    • Gusterberg (Ferro) (8042) – Austria/Czech Republic
    • ISN2016 (8086) - Iceland
    • SVY21 (4757) - Singapore
Parameters:
optional
Autocasts from Object

Specifies the attributes, spatial, and temporal filter of the query. When no parameters are passed to this method, all features in the client are returned. To only return features visible in the view, set the geometry parameter in the query object to the view's extent.

options Object
optional

An object with the following properties.

Specification:
optional

Signal object that can be used to abort the asynchronous task. The returned promise will be rejected with an Error named AbortError when an abort is signaled. See also AbortController for more information on how to construct a controller that can be used to deliver abort signals.

Returns:
TypeDescription
Promise<Object>When resolved, returns the extent and count of the features that satisfy the input query. See the object specification table below for details.
PropertyTypeDescription
countNumberThe number of features that satisfy the input query.
extentExtentThe extent of the features that satisfy the query.
Example:
var layer = new StreamLayer({
  url: streamLayerUrl  // URL to a stream service
});

view.whenLayerView(layer).then(function(layerView){
  layerView.watch("updating", function(val){
    if(!val){  // wait for the layer view to finish updating
      layerView.queryExtent().then(function(results){
        view.goTo(results.extent);  // go to the extent of all the graphics in the layer view
      });
    }
  });
});
queryFeatureCount(query, options){Promise<Number>}
Since: ArcGIS API for JavaScript 4.9

Executes a Query against features available for drawing in the layer view and returns the number of features that satisfy the query. If query parameters are not provided, the count of all features available for drawing is returned.

Known Limitations

  • Spatial queries have the same limitations as those listed in the projection engine documentation.
  • Spatial queries are not currently supported if the layer view has any of the following SpatialReferences:
    • GDM 2000 (4742) – Malaysia
    • Gusterberg (Ferro) (8042) – Austria/Czech Republic
    • ISN2016 (8086) - Iceland
    • SVY21 (4757) - Singapore
Parameters:
optional
Autocasts from Object

Specifies the attributes, spatial, and temporal filter of the query. When no parameters are passed to this method, all features in the client are returned. To only return features visible in the view, set the geometry parameter in the query object to the view's extent.

options Object
optional

An object with the following properties.

Specification:
optional

Signal object that can be used to abort the asynchronous task. The returned promise will be rejected with an Error named AbortError when an abort is signaled. See also AbortController for more information on how to construct a controller that can be used to deliver abort signals.

Returns:
TypeDescription
Promise<Number>When resolved, returns the number of features satisfying the query.
Examples:
view.on("click", function(event){

  var query = new Query();
  query.geometry = event.mapPoint;  // obtained from a view click event
  query.spatialRelationship = "intersects";

  view.whenLayerView(layer).then(function(layerView){
    watchUtils.whenNotOnce(layerView, "updating")
    .then(function(){
      return layerView.queryFeatureCount(query);
    })
    .then(function(count){
      console.log(count);  // prints the number of the client-side graphics that satisfy the query
    });
  });
});
view.whenLayerView(layer).then(function(layerView){
  return layerView.queryFeatureCount()
}).then(function(count){
  console.log(count);  // prints the total number of client-side graphics to the console
});
queryFeatures(query, options){Promise<FeatureSet>}
Since: ArcGIS API for JavaScript 4.9

Executes a Query against features available for drawing in the layer view and returns a FeatureSet. If query parameters are not provided, all features available for drawing are returned.

Known Limitations

  • Spatial queries have the same limitations as those listed in the projection engine documentation.
  • Spatial queries are not currently supported if the layer view has any of the following SpatialReferences:
    • GDM 2000 (4742) – Malaysia
    • Gusterberg (Ferro) (8042) – Austria/Czech Republic
    • ISN2016 (8086) - Iceland
    • SVY21 (4757) - Singapore
Parameters:
optional
Autocasts from Object

Specifies the attributes, spatial, and temporal filter of the query. When no parameters are passed to this method, all features in the client are returned. To only return features visible in the view, set the geometry parameter in the query object to the view's extent.

options Object
optional

An object with the following properties.

Specification:
optional

Signal object that can be used to abort the asynchronous task. The returned promise will be rejected with an Error named AbortError when an abort is signaled. See also AbortController for more information on how to construct a controller that can be used to deliver abort signals.

Returns:
TypeDescription
Promise<FeatureSet>When resolved, a FeatureSet containing an array of graphic features is returned.
Examples:
view.whenLayerView(layer).then(function(layerView){
  layerView.watch("updating", function(val){
    if(!val){  // wait for the layer view to finish updating
      layerView.queryFeatures(query).then(function(results){
        console.log(results.features);  // prints the array of client-side graphics to the console
      });
    }
  });
});
// returns all the graphics from the layer view
view.whenLayerView(layer).then(function(layerView){
  layerView.watch("updating", function(val){
    if(!val){  // wait for the layer view to finish updating
      layerView.queryFeatures().then(function(results){
        console.log(results.features);  // prints all the client-side graphics to the console
      });
    }
  });
});
queryLatestObservations(query, options){Promise<FeatureSet>}
Since: ArcGIS API for JavaScript 4.9

If a trackIdField is specified on the stream service, this method executes a Query against features available for drawing in the layer view and returns a FeatureSet of the latest observations for each trackId that satisfy the query. Otherwise, an Error will be thrown when the method is called.

Known Limitations

  • Spatial queries have the same limitations as those listed in the projection engine documentation.
  • Spatial queries are not currently supported if the layer view has any of the following SpatialReferences:
    • GDM 2000 (4742) – Malaysia
    • Gusterberg (Ferro) (8042) – Austria/Czech Republic
    • ISN2016 (8086) - Iceland
    • SVY21 (4757) - Singapore
Parameters:
optional
Autocasts from Object

Specifies the attributes, spatial, and temporal filter of the query. When no parameters are passed to this method, all features in the client are returned. To only return features visible in the view, set the geometry parameter in the query object to the view's extent.

options Object
optional

An object with the following properties.

Specification:
optional

Signal object that can be used to abort the asynchronous task. The returned promise will be rejected with an Error named AbortError when an abort is signaled. See also AbortController for more information on how to construct a controller that can be used to deliver abort signals.

Returns:
TypeDescription
Promise<FeatureSet>When resolved, returns the FeatureSet that satisfy the input query.
Example:
var layer = new StreamLayer({
  url: streamLayerUrl  // URL to a Stream Service
});

view.whenLayerView(layer).then(function(layerView){
  layerView.watch("updating", function(val){
    if(!val){  // wait for the layer view to finish updating
      layerView.queryLatestObservations().then(function(results){
        console.log(results.features);  // prints all the client-side graphics to the console
      });
    }
  });
});
queryObjectIds(query, options){Promise<Number[]>}
Since: ArcGIS API for JavaScript 4.9

Executes a Query against features available for drawing in the layer view and returns array of the ObjectIDs of features that satisfy the input query. If query parameters are not provided, the ObjectIDs of all features available for drawing are returned.

Known Limitations

  • Spatial queries have the same limitations as those listed in the projection engine documentation.
  • Spatial queries are not currently supported if the layer view has any of the following SpatialReferences:
    • GDM 2000 (4742) – Malaysia
    • Gusterberg (Ferro) (8042) – Austria/Czech Republic
    • ISN2016 (8086) - Iceland
    • SVY21 (4757) - Singapore
Parameters:
optional
Autocasts from Object

Specifies the attributes, spatial, and temporal filter of the query. When no parameters are passed to this method, all features in the client are returned. To only return features visible in the view, set the geometry parameter in the query object to the view's extent.

options Object
optional

An object with the following properties.

Specification:
optional

Signal object that can be used to abort the asynchronous task. The returned promise will be rejected with an Error named AbortError when an abort is signaled. See also AbortController for more information on how to construct a controller that can be used to deliver abort signals.

Returns:
TypeDescription
Promise<Number[]>When resolved, returns an array of numbers representing the ObjectIDs of the features satisfying the query.
Examples:
view.on("click", function(event){

  var query = new Query();
  query.geometry = event.mapPoint;  // obtained from a view click event
  query.spatialRelationship = "intersects";

  view.whenLayerView(layer).then(function(layerView){
    watchUtils.whenNotOnce(layerView, "updating")
    .then(function(){
      return layerView.queryObjectIds(query);
    })
    .then(function(ids){
      console.log(ids);  // prints the ids of the client-side graphics to the console
    });
  });
});
// returns all the Ids from the graphics in the layer view
view.whenLayerView(layer).then(function(layerView){
  return layerView.queryObjectIds()
}).then(function(ids){
  console.log(ids);  // prints the ids of all the client-side graphics to the console
});
when(callback, errback){Promise}inherited
Since: ArcGIS API for JavaScript 4.6

when() may be leveraged once an instance of the class is created. This method takes two input parameters: a callback function and an errback function. The callback executes when the instance of the class loads. The errback executes if the instance of the class fails to load.

Parameters:
callback Function
optional

The function to call when the promise resolves.

errback Function
optional

The function to execute when the promise fails.

Returns:
TypeDescription
PromiseReturns a new promise for the result of callback that may be used to chain additional functions.
Example:
// Although this example uses MapView, any class instance that is a promise may use when() in the same way
var view = new MapView();
view.when(function(){
  // This function will execute once the promise is resolved
}, function(error){
  // This function will execute if the promise is rejected due to an error
});

Event Overview

NameTypeSummaryClass
{attributes: Object,geometry: Object}

Fires when the layer view receives data.

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more detailsStreamLayerView
{client: Number,websocket: Number}

Fires after the layer starts receiving updates from the stream service.

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more detailsStreamLayerView

Event Details

data-received

Fires when the layer view receives data. The event object contains the message properties received from the stream service.

Properties:
attributes Object

Name-value pairs of fields and field values associated with the received data.

geometry Object

A location of the received data containing x, y coordinates and the spatial reference wkid.

update-rate
Since: ArcGIS API for JavaScript 4.17

Fires after the layer starts receiving updates from the stream service. It will return the websocket and the client update rates. The update rate indicates number of features are being pushed from the server and being processed on the client right. The client update rate will be approximately equal to the websocket update rate unless the service is pushing updates at a rate faster than the client can handle. In which case, the API will down-throttle the update rate and will cause the client update rate to be lower.

Properties:
client Number

The client update rate. Returns number of features being processed on the client.

websocket Number

Update rate for websocket/service. Returns number of features being pushed from the server.

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