BasemapLayerList

The BasemapLayerList widget provides a way to display a list of Basemap layers and switch on/off their visibility. Base layers and reference layers are divided into separate sections. When editing is enabled, layers can be reordered by dragging and dropping between the lists and the title can be edited.

BasemapLayerList is very similar to our LayerList widget. See below samples for code inspiration:
Sample - LayerList widget
Sample - LayerList widget with actions

See also:

Example:

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

Constructors

new BasemapLayerList(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 BasemapLayerList = new BasemapLayerList({
  view: view
});

Property Overview

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

Show inherited properties

Hide inherited properties

Type	Summary	Class
Collection<ListItem>	more details A collection of ListItems representing the baseLayers.	more details	BasemapLayerList
ListItemCreatedHandler	more details Specifies a function that accesses each ListItem representing a base layer.	more details	BasemapLayerList
String	more details The current basemap's title.	more details	BasemapLayerList
String\|HTMLElement	more details The ID or node representing the DOM element containing the widget.	more details	Widget
String	more details The name of the class.	more details	Accessor
Boolean	more details Indicates whether the basemap’s title, layer order and layer grouping can be edited by the user.	more details	BasemapLayerList
Number	more details Indicates the heading level to use for the widget title (i.e.	more details	BasemapLayerList
String	more details The widget's default CSS icon class.	more details	BasemapLayerList
String	more details The unique ID assigned to the widget when the widget is created.	more details	Widget
String	more details The widget's default label.	more details	BasemapLayerList
Boolean	more details Indicates whether more than one list item may be selected by the user at a single time.	more details	BasemapLayerList
Collection<ListItem>	more details A collection of ListItems representing the referenceLayers.	more details	BasemapLayerList
ListItemCreatedHandler	more details Specifies a function that accesses each ListItem representing a reference layer.	more details	BasemapLayerList
Collection<ListItem>	more details A collection of selected ListItems representing basemap layers selected by the user.	more details	BasemapLayerList
MapView\|SceneView	more details A reference to the MapView or SceneView.	more details	BasemapLayerList
BasemapLayerListViewModel	more details The view model for this widget.	more details	BasemapLayerList
Boolean	more details Indicates whether the widget is visible.	more details	Widget
VisibleElements	more details The visible elements that are displayed within the widget.	more details	BasemapLayerList

Property Details

baseItems Collection<ListItem>readonly

A collection of ListItems representing the baseLayers.

baseListItemCreatedFunction ListItemCreatedHandler

Specifies a function that accesses each ListItem representing a base layer. Each list item's modifiable properties can be updated within. Actions can be added to list items using the actionsSections property of the ListItem.

Example:

let bmLayerList = new BasemapLayerList({
  view: view,
  editingEnabled: true,
  baseListItemCreatedFunction: function(event){
    baseListItem = event.item;
    if(baseListItem.title === "World Imagery_01"){
      // clean up title
      baseListItem.title = "World Imagery";
      // open the baseList item
      baseListItem.open = true;
    }
  }
})

basemapTitle String

The current basemap's title.

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

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

editingEnabled Boolean

Indicates whether the basemap’s title, layer order and layer grouping can be edited by the user. Any edits made will only be shown locally and will not be saved.

Default Value:false

Example:

// to enable editing
basemapLayerList.editingEnabled = true;

headingLevel Number Since: ArcGIS API for JavaScript 4.20

Indicates the heading level to use for the widget title (i.e. "Basemap"). By default, this is rendered as a level 2 heading (e.g. <h2>Basemap</h2>). Depending on the widget's placement in your app, you may need to adjust this heading for proper semantics. This is important for meeting accessibility standards.

Default Value:2

See also:

Heading Elements

Example:

// the widget title will render as an <h3>
basemapLayerList.headingLevel = 3;

iconClass String

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

The widget's default label.

multipleSelectionEnabled Boolean

Indicates whether more than one list item may be selected by the user at a single time. Selected items are available in the selectedItems property.

Default Value:false

See also:

selectedItems

Example:

basemapLayerList.multipleSelectionEnabled = true;

referenceItems Collection<ListItem>readonly

A collection of ListItems representing the referenceLayers.

referenceListItemCreatedFunction ListItemCreatedHandler

Specifies a function that accesses each ListItem representing a reference layer. Each list item's modifiable properties can be updated within. Actions can be added to list items using the actionsSections property of the ListItem.

Example:

let bmLayerList = new BasemapLayerList({
  view: view,
  editingEnabled: true,
  referenceListItemCreatedFunction: function(event){
    referenceListItem = event.item;
    if(referenceListItem.title === "World Imagery_01_reference_layer"){
      // clean up title
      referenceListItem.title = "Reference layer";
      // open the baseList item
      referenceListItem.open = true;
    }
  }
})

selectedItems Collection<ListItem>

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

view MapView|SceneView

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

viewModel BasemapLayerListViewModel

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 BasemapLayerListViewModel 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 VisibleElementsautocast Since: ArcGIS API 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:

basemapLayerList.visibleElements = {
  statusIndicators: false
};

Method Overview

Show inherited methods

Hide inherited methods

Return Type	Summary	Class
String	more details A utility method used for building the value for a widget's `class` property.	more details	Widget
	more details Destroys the widget instance.	more details	Widget
Boolean	more details Emits an event on the instance.	more details	Widget
Boolean	more details Indicates whether there is an event listener on the instance that matches the provided event name.	more details	Widget
Boolean	more details `isFulfilled()` may be used to verify if creating an instance of the class is fulfilled (either resolved or rejected).	more details	Widget
Boolean	more details `isRejected()` may be used to verify if creating an instance of the class is rejected.	more details	Widget
Boolean	more details `isResolved()` may be used to verify if creating an instance of the class is resolved.	more details	Widget
Object	more details Registers an event handler on the instance.	more details	Widget
	more details Widget teardown helper.	more details	Widget
	more details This method is primarily used by developers when implementing custom widgets.	more details	Widget
Object	more details This method is primarily used by developers when implementing custom widgets.	more details	Widget
	more details Renders widget to the DOM immediately.	more details	Widget
	more details This method is primarily used by developers when implementing custom widgets.	more details	Widget
	more details Triggers the trigger-action event and executes the given action or action toggle.	more details	BasemapLayerList
Promise	more details `when()` may be leveraged once an instance of the class is created.	more details	Widget

Method Details

classes(classNames){String}inherited

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

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.

isFulfilled(){Boolean}inherited Since: ArcGIS API 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 API 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 API 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(handles)inherited

Widget teardown helper. Any handles added to it will be automatically removed when the widget is destroyed.

Parameter:

handles 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.

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 API 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` that may be used to chain additional functions.

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 baseListItemCreatedFunction and referenceListItemCreatedFunction properties. See the example snippets in the documentations for those properties 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 to the status indicators will be displayed. Default is true.

baseLayers Boolean

optional

Indicates whether to the base layers will be displayed. Default is true.

referenceLayers Boolean

optional

Indicates whether to the reference layers will be displayed. Default is true.

Event Overview

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

Event Details

trigger-action

Fires after the user clicks on an action or action toggle inside the BasemapLayerList 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 API for JavaScriptAPI Reference

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