StreamLayerView

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

The StreamLayerView provides methods for connecting, disconnecting, and filtering data received from a stream service for a layer view associated with a StreamLayer.

The StreamLayer extends the FeatureLayer to add the ability to connect to a stream of data using HTML5 WebSockets. It connects to a server that emits geographic features continuously. While the FeatureLayer is used to map relatively static data, 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.

WebSockets are a feature of HTML5. Most browsers are supporting WebSockets in recent versions. However, they are not supported by all versions of all browsers. To get more information about WebSockets and to test if a browser supports WebSockets, visit WebSocket.org.

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
Object

Contains the attribute and spatial filters used to filter messages sent to the given layer view by a stream service.

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more detailsStreamLayerView
Collection<Graphic>

Contains the collection of graphics visible in the layer view for the live stream.

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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

connectionErrorErrorreadonly

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

connectionStatusStringreadonly

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

declaredClassStringreadonly inherited

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

filterObjectreadonly

Contains the attribute and spatial filters used to filter messages sent to the given layer view by a stream service. To change the filter for only a single layer view, use the updateFilter() method. The layer view's filter is always updated when the updateFilter() method of the associated stream layer instance is called.

Properties:
geometry Extent
optional

A spatial filter for filtering features. Only features that intersect the given geometry are displayed in the view.

where String
optional

A SQL where clause used to filter features by attributes.

See also:

Contains the collection of graphics visible in the layer view for the live stream. Graphics may be removed from the layer view by calling the removeAll() method from Collection.

Example:
// removes all stream layer graphics from view
// new messages add features to the view
view.whenLayerView(streamLayer)
  .then(function(layerView){
    layer.graphics.removeAll();
  });

layerLayerreadonly inherited

The layer being viewed.

suspendedBooleanreadonly inherited

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

updatingBooleanreadonly 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
Promise

An instance of this class is a Promise.

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more detailsLayerView
Promise

Opens a web socket connection with the stream service to start receiving messages.

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more detailsStreamLayerView

Closes the web socket connection with the stream service.

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more detailsStreamLayerView

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
Object

Highlights the given feature(s).

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more detailsStreamLayerView
Boolean

An instance of this class is a Promise.

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more detailsLayerView
Boolean

An instance of this class is a Promise.

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more detailsLayerView
Boolean

An instance of this class is a Promise.

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more detailsLayerView
Object

Registers an event handler on the instance.

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more detailsStreamLayerView
Promise

An instance of this class is a Promise.

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more detailsLayerView
Promise

An instance of this class is a Promise.

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more detailsLayerView
Promise<Object>

Updates the filter on the StreamLayerView.

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more detailsStreamLayerView

Method Details

always(callbackOrErrback){Promise}inherited

An instance of this class is a Promise. Therefore always() may be used to execute a function if the promise is rejected or resolved. The input function will always execute no matter the response. For more information about promises, see the Working with Promises guide page.

Parameter:
callbackOrErrback Function
optional

The function to execute when the promise is rejected or resolved.

Returns:
TypeDescription
PromiseReturns a new promise for the result of callbackOrErrback.
Example:
// Although this example uses MapView, any class instance that is a promise may use always() in the same way
var view = new MapView();
view.always(function(){
  // This function will always execute whether or not the promise is resolved or rejected
});

connect(){Promise}

Opens a web socket connection with the stream service to start receiving messages. This is called internally when the StreamLayer is added to a view.

Returns:
TypeDescription
PromiseThe promise is resolved if the connection is successful or rejected with an error if the connection failed

disconnect()

Closes the web socket connection with the stream service. This is called internally when the StreamLayer is removed from a view.

To verify when the connection is closed, watch the connectionStatus property.

emit(type, event)protected

Since: ArcGIS API for JavaScript 4.5

Emits an event on the instance. This method should only be used when creating subclasses that inherit from Evented.

Parameters:
type String

The name of the event.

event Object

The event payload.

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){Object}

Highlights the given feature(s).

Known Limitations

Currently the highlight method is only supported in a SceneView.

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
ObjectReturns a highlight handler with a remove() method that can be called to remove the highlight.
PropertyTypeDescription
removeFunctionWhen called, removes the highlight of the selected graphics.
See also:
Example:
// highlight feature on click
view.on("click", function(event){
 view.hitTest(event).then(function(response){
   if (response.results[0]) {
     var graphic = response.results[0].graphic;
     view.whenLayerView(graphic.layer).then(function(lyrView){
       lyrView.highlight(graphic);
     })
   }
 })
});

isFulfilled(){Boolean}inherited

An instance of this class is a Promise. Therefore isFulfilled() may be used to verify if the promise is fulfilled (either resolved or rejected). If it is fulfilled, true will be returned. See the Working with Promises guide page for more information about promises.

Returns:
TypeDescription
BooleanIndicates whether the promise has been fulfilled (either resolved or rejected).

isRejected(){Boolean}inherited

An instance of this class is a Promise. Therefore isRejected() may be used to verify if the promise is rejected. If it is rejected, true will be returned. See the Working with Promises guide page for more information about promises.

Returns:
TypeDescription
BooleanIndicates whether the promise has been rejected.

isResolved(){Boolean}inherited

An instance of this class is a Promise. Therefore isResolved() may be used to verify if the promise is resolved. If it is resolved, true will be returned. See the Working with Promises guide page for more information about promises.

Returns:
TypeDescription
BooleanIndicates whether the promise has been resolved.

on(type, listener){Object}

Registers an event handler on the instance. Call this method to hook an event with a listener. See the Events summary table for a list of listened events.

Parameters:
type String

The name of event 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.
PropertyTypeDescription
removeFunctionWhen called, removes the listener from the event.
See also:
Example:
view.on("click", function(event){
  // event is the event handle returned after the event fires.
  console.log(event.mapPoint);
});

otherwise(errback){Promise}inherited

An instance of this class is a Promise. Use otherwise() to call a function once the promise is rejected.

Parameter:
errback Function
optional

The function to execute when the promise fails.

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

then(callback, errback, progback){Promise}inherited

An instance of this class is a Promise. Therefore then() 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 promise resolves (when the instance of the class loads). The errback executes if the promise fails. See the Working with Promises guide page for additional details.

Parameters:
callback Function
optional

The function to call when the promise resolves.

errback Function
optional

The function to execute when the promise fails.

progback Function
optional

The function to invoke when the promise emits a progress update.

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 then() in the same way
var view = new MapView();
view.then(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
});

updateFilter(filter){Promise<Object>}

Updates the filter on the StreamLayerView. The filter is updated only on the layer view from which it is called. To update the filter on all layer views generated from a common layer, use the StreamLayer.updateFilter() method. If the input filter object is undefined or null, the spatial and attribute filters are removed.

Filter changes only apply to incoming features. Features already displayed in the view are not filtered. Therefore, you may want to clear the graphics in the layer view prior to applying a new filter. To do so, get the layer view then call removeAll() on the StreamLayerView.graphics. You may also filter features already present in the view using the Collection methods. See the examples below.

Parameters:
filter Object

Updates the spatial and attribute filters. If null, all filters are cleared.

Specification:
geometry Extent
optional

A spatial filter for filtering features. Only features that intersect the given geometry are displayed in the view. If null, the spatial filter is cleared.

where String
optional

A SQL where clause used to filter features by attributes. If null, the attribute filter is cleared.

Returns:
TypeDescription
Promise< Object>Resolves to an object that has a filter property, indicating the filter set on the stream service by the layer view. If the filter could not be updated, the promise is rejected with an error that explains why the filter failed to update.
See also:
Examples:
view.whenLayerView(layer)
 .then(function(layerView){
   layerView.graphics.removeAll();

   // updates the spatial filter based on the current view's extent
   // and removes the attribute filter
   layerView.updateFilter({
     geometry: view.extent.filter(),
     where: null
   });
 });
// updates the attribute filter to only display features whose
// route ID is 110
layerView.updateFilter({
  where: "ROUTE_ID = 110"
});
// clears all filters from the layer
layerView.updateFilter(null);

Event Overview

NameTypeSummaryClass

Fires when the layer view receives data.

more details
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.

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