LayerList

The LayerList widget provides a way to display a list of layers, and switch on/off their visibility. The ListItem API provides access to each layer's properties, allows the developer to configure actions related to the layer, and allows the developer to add content to the item related to the layer.

To hide layers in the map from the LayerList widget, you must set the listMode property on the desired layers to hide.

See also

Example

let layerList = new LayerList({
  view: view
});
// Adds widget below other elements in the top left corner of the view
view.ui.add(layerList, {
  position: "top-left"
});

Constructors

new LayerList(properties)

Parameter

properties Object

optional

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

Example

// typical usage
let layerlist = new LayerList({
  view: view
});

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\|HTMLElement	The ID or node representing the DOM element containing the widget. more details	Widget
String	The name of the class. more details	Accessor
String	The widget's default CSS icon class. more details	LayerList
String	The unique ID assigned to the widget when the widget is created. more details	Widget
String	The widget's default label. more details	LayerList
ListItemCreatedHandler	A function that executes each time a ListItem is created. more details	LayerList
Boolean	Indicates whether more than one list item may be selected by the user at a single time. more details	LayerList
Collection<ListItem>	A collection of ListItems representing operational layers. more details	LayerList
Collection<ListItem>	A collection of selected ListItems representing operational layers selected by the user. more details	LayerList
Boolean	Indicates whether list items may be selected by the user. more details	LayerList
MapView\|SceneView	A reference to the MapView or SceneView. more details	LayerList
LayerListViewModel	The view model for this widget. more details	LayerList
Boolean	Indicates whether the widget is visible. more details	Widget
VisibleElements	The visible elements that are displayed within the widget. more details	LayerList

Property Details

container String|HTMLElement inherited

The ID or node representing the DOM element containing the widget. This property can only be set once. The following examples are all valid use cases when working with widgets.

Examples

// Create the HTML div element programmatically at runtime and set to the widget's container
const basemapGallery = new BasemapGallery({
  view: view,
  container: document.createElement("div")
});

// Add the widget to the top-right corner of the view
view.ui.add(basemapGallery, {
  position: "top-right"
});

// Specify an already-defined HTML div element in the widget's container

const basemapGallery = new BasemapGallery({
  view: view,
  container: basemapGalleryDiv
});

// Add the widget to the top-right corner of the view
view.ui.add(basemapGallery, {
  position: "top-right"
});

// HTML markup
<body>
  <div id="viewDiv"></div>
  <div id="basemapGalleryDiv"></div>
</body>

// Specify the widget while adding to the view's UI
const basemapGallery = new BasemapGallery({
  view: view
});

// Add the widget to the top-right corner of the view
view.ui.add(basemapGallery, {
  position: "top-right"
});

declaredClass Stringreadonly inherited Since: ArcGIS Maps SDK for JavaScript 4.7

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

iconClass String Since: ArcGIS Maps SDK for JavaScript 4.7

The widget's default CSS icon class.

id String inherited

The unique ID assigned to the widget when the widget is created. If not set by the developer, it will default to the container ID, or if that is not present then it will be automatically generated.

label String Since: ArcGIS Maps SDK for JavaScript 4.7

The widget's default label.

listItemCreatedFunction ListItemCreatedHandler Since: ArcGIS Maps SDK for JavaScript 4.4

A function that executes each time a ListItem is created. Use this function to add actions and panels to list items, and to override the default settings of a list item. Actions can be added to list items using the actionsSections property of the ListItem.

See also

Sample - LayerList widget with actions

Example

let layerList = new LayerList({
  view: view,
  // executes for each ListItem in the LayerList
  listItemCreatedFunction: function (event) {

    // The event object contains properties of the
    // layer in the LayerList widget.

    let item = event.item;

    if (item.title === "US Demographics") {
      // open the list item in the LayerList
      item.open = true;
      // change the title to something more descriptive
      item.title = "Population by county";
      // set an action for zooming to the full extent of the layer
      item.actionsSections = [[{
        title: "Go to full extent",
        className: "esri-icon-zoom-out-fixed",
        id: "full-extent"
      }]];
    }
  }
});

multipleSelectionEnabled Boolean

Indicates whether more than one list item may be selected by the user at a single time. You must first set selectionEnabled to true for this property to have an effect on the widget.

Selected items are available in the selectedItems property.

Default Value:false

See also

selectionEnabled
selectedItems

Example

layerList.selectionEnabled = true;
layerList.multipleSelectionEnabled = true;

operationalItems Collection<ListItem>readonly

A collection of ListItems representing operational layers. To hide layers from the LayerList widget, set the listMode property on the layer(s) to hide.

See also

Layer.listMode

selectedItems Collection<ListItem>

A collection of selected ListItems representing operational layers selected by the user.

See also

selectionEnabled

selectionEnabled Boolean

Indicates whether list items may be selected by the user. Selected items may be reordered in the list by dragging gestures with the mouse or touch screen, or with arrow keys on the keyboard.

Selected items are available in the selectedItems property.

Default Value:false

See also

selectedItems

Example

layerList.selectionEnabled = true;

view MapView|SceneView

A reference to the MapView or SceneView. Set this to link the widget to a specific view.

viewModel LayerListViewModel

The view model for this widget. This is a class that contains all the logic (properties and methods) that controls this widget's behavior. See the LayerListViewModel class to access all properties and methods on the widget.

visible Boolean inherited

Indicates whether the widget is visible.

If false, the widget will no longer be rendered in the web document. This may affect the layout of other elements or widgets in the document. For example, if this widget is the first of three widgets associated to the upper right hand corner of the view UI, then the other widgets will reposition when this widget is made invisible. For more information, refer to the CSS display value of "none".

Default Value:true

Example

// Hides the widget in the view
widget.visible = false;

visibleElements VisibleElements Since: ArcGIS Maps SDK for JavaScript 4.15

The visible elements that are displayed within the widget. This property provides the ability to turn individual elements of the widget's display on/off.

Example

layerList.visibleElements = {
  statusIndicators: false,
  errors: true
};

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. more details	Accessor
String	A utility method used for building the value for a widget's `class` property. more details	Widget
	Destroys the widget instance. more details	Widget
Boolean	Emits an event on the instance. more details	Widget
Boolean	Indicates whether there is an event listener on the instance that matches the provided event name. more details	Widget
Boolean	Returns true if a named group of handles exist. more details	Accessor
Boolean	`isFulfilled()` may be used to verify if creating an instance of the class is fulfilled (either resolved or rejected). more details	Widget
Boolean	`isRejected()` may be used to verify if creating an instance of the class is rejected. more details	Widget
Boolean	`isResolved()` may be used to verify if creating an instance of the class is resolved. more details	Widget
Object	Registers an event handler on the instance. more details	Widget
	Adds one or more handles which are to be tied to the lifecycle of the widget. more details	Widget
	This method is primarily used by developers when implementing custom widgets. more details	Widget
	Removes a group of handles owned by the object. more details	Accessor
Object	This method is primarily used by developers when implementing custom widgets. more details	Widget
	Renders widget to the DOM immediately. more details	Widget
	This method is primarily used by developers when implementing custom widgets. more details	Widget
	Triggers the trigger-action event and executes the given action or action toggle. more details	LayerList
Promise	`when()` may be leveraged once an instance of the class is created. more details	Widget

Method Details

addHandles(handleOrHandles, groupKey)inherited Since: ArcGIS Maps SDK for JavaScript 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.

classes(classNames){String}inherited Since: ArcGIS Maps SDK for JavaScript 4.7

A utility method used for building the value for a widget's class property. This aids in simplifying CSS class setup.

Parameter

classNames String|String []|Object

repeatable

The class names.

Returns

Type	Description
String	The computed class name.

See also

Guide - Widget development (rendering)

Example

// .tsx syntax showing how to set CSS classes while rendering the widget

render() {
  const dynamicIconClasses = {
    [CSS.myIcon]: this.showIcon,
    [CSS.greyIcon]: !this.showIcon
  };

  return (
    <div class={classes(CSS.root, CSS.mixin, dynamicIconClasses)} />
  );
}

destroy()inherited

Destroys the widget instance.

emit(type, event){Boolean}inherited Since: ArcGIS Maps SDK 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

Type	Description
Boolean	`true` if a listener was notified

hasEventListener(type){Boolean}inherited

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(groupKey){Boolean}inherited Since: ArcGIS Maps SDK for JavaScript 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");
}

isFulfilled(){Boolean}inherited Since: ArcGIS Maps SDK for JavaScript 4.19

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

Type	Description
Boolean	Indicates whether creating an instance of the class has been fulfilled (either resolved or rejected).

isRejected(){Boolean}inherited Since: ArcGIS Maps SDK for JavaScript 4.19

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

Returns

Type	Description
Boolean	Indicates whether creating an instance of the class has been rejected.

isResolved(){Boolean}inherited Since: ArcGIS Maps SDK for JavaScript 4.19

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

Returns

Type	Description
Boolean	Indicates whether creating an instance of the class has been resolved.

on(type, listener){Object}inherited

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);
});

own(handleOrHandles)inherited Since: ArcGIS Maps SDK for JavaScript 4.24

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

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

this.own(handle); // Handle gets removed when the widget is destroyed.

Parameter

handleOrHandles WatchHandle|WatchHandle []

Handles marked for removal once the widget is destroyed.

postInitialize()inherited

This method is primarily used by developers when implementing custom widgets. Executes after widget is ready for rendering.

removeHandles(groupKey)inherited Since: ArcGIS Maps SDK for JavaScript 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");

render(){Object}inherited

This method is primarily used by developers when implementing custom widgets. It must be implemented by subclasses for rendering.

Returns

Type	Description
Object	The rendered virtual node.

renderNow()inherited

Renders widget to the DOM immediately.

scheduleRender()inherited

This method is primarily used by developers when implementing custom widgets. Schedules widget rendering. This method is useful for changes affecting the UI.

triggerAction(action, item)

Triggers the trigger-action event and executes the given action or action toggle.

Parameters

action ActionButton|ActionToggle

The action to execute.

item ListItem

An item associated with the action.

when(callback, errback){Promise}inherited Since: ArcGIS Maps SDK for JavaScript 4.19

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

Type	Description
Promise	Returns a new promise for the result of `callback`.

Example

// Although this example uses the BasemapGallery widget, any class instance that is a promise may use when() in the same way
let bmGallery = new BasemapGallery();
bmGallery.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
});

Type Definitions

ListItemCreatedHandler(event)

Function definition for the listItemCreatedFunction property. See the example snippet in the listItemCreatedFunction documentation for more details.

Parameters

event Object

An object containing a list item created by the LayerList.

Specification

item ListItem

A list item created by the LayerList. You can modify the properties of this item to customize the text, actions, panel content, and visibility of the list item. See the documentation for the listItemCreatedFunction for more details.

VisibleElements

The visible elements that are displayed within the widget. This provides the ability to turn individual elements of the widget's display on/off.

Properties

statusIndicators Boolean

optional

Indicates whether the status indicators will be displayed. Default is true.

errors Boolean

optional

Since 4.25 Indicates whether layer load errors will be displayed. Default is false.

Event Overview

Name	Type	Summary	Class
	{action: ActionButton\|ActionToggle,item: ListItem}	Fires after the user clicks on an action or action toggle inside the LayerList widget. more details	LayerList

Event Details

trigger-action

Fires after the user clicks on an action or action toggle inside the LayerList widget. This event may be used to define a custom function to execute when particular actions are clicked.

Properties

action ActionButton|ActionToggle

The action clicked by the user.

item ListItem

The ListItem associated with the action.

ArcGIS Maps SDK for JavaScriptAPI Reference

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