The Legend widget describes the symbols used to represent layers in a map. All symbols and text used in this widget are configured in the Renderer of the layer. The legend will only display layers and sublayers that are visible in the view.
The legend automatically updates when
- the visibility of a layer or sublayer changes
- a layer is added or removed from the map
- a layer's
renderer
,opacity
, ortitle
is changed - the
legendEnabled
property is changed (set totrue
orfalse
on the layer)
You can use the view's DefaultUI to add widgets to the view's user interface via the ui property on the view.
Known Limitations
- Currently, the legend widget does not support the following layer types: ElevationLayer, GraphicsLayer, IntegratedMeshLayer, KMLLayer, MapNotesLayer, OpenStreetMapLayer, VectorTileLayer, and WebTileLayer.
- 3D symbols with more than one symbol layer are not supported.
- DictionaryRenderer is not supported.
Expand the "Read more" section below to view various examples of legends based on renderer type.
- See also:
let legend = new Legend({
view: view
});
view.ui.add(legend, "bottom-right");
Constructors
-
new Legend(properties)
-
Parameter:properties Objectoptional
See the properties for a list of all the properties that may be passed into the constructor.
Example:// typical usage let legend = new Legend({ view: view });
Property Overview
Name | Type | Summary | Class | |
---|---|---|---|---|
Collection<ActiveLayerInfo> | more details Collection of ActiveLayerInfo objects used by the legend view to display data in the legend. | more details | Legend | |
Boolean | more details Indicates whether to show the Basemap layers in the Legend. | more details | Legend | |
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 | |
Number | more details Indicates the heading level to use for the legend title. | more details | Legend | |
Boolean | more details When | more details | Legend | |
String | more details The widget's default CSS icon class. | more details | Legend | |
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 | Legend | |
Object[] | more details Specifies a subset of the layers to display in the legend. | more details | Legend | |
Boolean | more details Determines whether to respect the properties of the layers in the map that control the legend's visibility ( | more details | Legend | |
Object|String | more details Indicates the style of the legend. | more details | Legend | |
MapView|SceneView | more details | more details | Legend | |
LegendViewModel | more details The view model for this widget. | more details | Legend | |
Boolean | more details Indicates whether the widget is visible. | more details | Widget |
Property Details
-
activeLayerInfos Collection<ActiveLayerInfo>autocast
-
Collection of ActiveLayerInfo objects used by the legend view to display data in the legend. The legend widget watches this property to hide or display the layer's legend when an ActiveLayerInfo is removed from or added to this collection.
-
basemapLegendVisible Boolean
-
Indicates whether to show the Basemap layers in the Legend. If you set this property to
true
and specify layerInfos, the basemap layers you want included in the legend must also be specified inlayerInfos
.- Default Value:false
Example:legend.basemapLegendVisible = true;
-
-
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" });
-
Since: ArcGIS API for JavaScript 4.7
-
The name of the class. The declared class name is formatted as
esri.folder.className
.
-
headingLevel NumberSince: ArcGIS API for JavaScript 4.20
-
Indicates the heading level to use for the legend title. By default, legend titles are rendered as level 3 headings (e.g.
<h3>Legend title</h3>
). Depending on the legend placement in your app, you may need to adjust this heading for proper semantics. This is important for meeting accessibility standards.- Default Value:3
- See also:
Example:// legend title will render as an <h2> legend.headingLevel = 2;
-
hideLayersNotInCurrentView BooleanSince: ArcGIS API for JavaScript 4.21
-
When
true
, layers will only be shown in the legend if they are visible in the view's extent. When data from a layer is not visible in the view, the layer's legend information will be hidden.To hide layers completely from the legend, you should set the
legendEnabled
property of the layer tofalse
.- Default Value:false
- See also:
Example:// layers not displayed in the view // will not be shown in the legend legend.hideLayersNotInCurrentView = true;
-
iconClass StringSince: ArcGIS API for JavaScript 4.7
-
The widget's default CSS icon class.
-
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 StringSince: ArcGIS API for JavaScript 4.7
-
The widget's default label.
-
Specifies a subset of the layers to display in the legend. This includes any basemap layers you want to be visible in the legend. If this property is not set, all layers in the map will display in the legend, including basemap layers if basemapLegendVisible is
true
. Objects in this array are defined with the properties listed below.- Properties:
-
title String
Specifies a title for the layer to display above its symbols and descriptions. If no title is specified the service name is used.
layer LayerA layer to display in the legend.
optional Only applicable if the
layer
is a MapImageLayer. The IDs of the MapImageLayer sublayers for which to display legend information. Since version 4.23.
-
respectLayerVisibility BooleanSince: ArcGIS API for JavaScript 4.13
-
Determines whether to respect the properties of the layers in the map that control the legend's visibility (
minScale
,maxScale
,legendEnabled
). By default, a layer's legend elements will not render in the legend given the following conditions:- The layer's legendEnabled property
is set to
false
. - If the view's scale is outside the visibility range defined by the layer's minScale and maxScale properties.
When the
respectLayerVisibility
property of the legend is set tofalse
, the legend elements for each layer in the map will always display, thus disregarding theminScale
,maxScale
, andlegendEnabled
properties for each layer in the map.- Default Value:true
- See also:
Example:// Always displays legend elements for the map's layers // regardless of their minScale, maxScale, and legendEnabled properties legend.respectLayerVisibility = false;
- The layer's legendEnabled property
is set to
-
Since: ArcGIS API for JavaScript 4.7
-
Indicates the style of the legend. The style determines the legend's layout and behavior. You can either specify a string or an object to indicate the style. The known string values are the same values listed in the table within the
type
property.- Properties:
-
type String
Specifies the style of the legend. There are two possible values listed in the table below:
Value Description classic The legend has a portrait orientation. The user can scroll vertically when many elements are included in the legend's content. card In wide views, the legend has a landscape orientation that allows users to scroll horizontally to view all legend elements. This style can be responsive, making it ideal for mobile web apps. In smaller views, the legend collapses to occupy less space. One element is shown at a time in a card-style layout, which the user can navigate horizontally. Possible Values:"classic"|"card"
layout StringDefault Value:stackWhen a
card
type is specified, you can specify one of the following layout options.Value Description auto This layout is responsive so that in wide views the legend has a side-by-side
layout, and astack
layout in smaller (mobile) views.side-by-side The legend has a landscape orientation that allows users to scroll horizontally to view multiple legend cards at a time. stack The legend cards are stacked, which conserves space, but restricts the user to seeing only one card at a time. Possible Values:"auto"|"side-by-side"|"stack"
- Default Value:classic
Examples:// renders the legend in the card style with a "stack" layout legend.style = "card";
// renders the legend in the card style with a responsive // layout that toggles between "stack" and "side-by-side" legend.style = { type: "card", layout: "auto" };
// renders the legend in the classic layout legend.style = "classic";
-
viewModel LegendViewModelautocast
-
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 LegendViewModel class to access all properties and methods on the widget.
-
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;
Method Overview
Name | Return Type | Summary | Class | |
---|---|---|---|---|
String | more details A utility method used for building the value for a widget's | 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
| more details | Widget | |
Boolean | more details
| more details | Widget | |
Boolean | more details
| 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 | ||
Promise | more details
| more details | Widget |
Method Details
-
Since: ArcGIS API 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:repeatable The class names.
Returns:Type Description String The computed class name. - See also:
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.
-
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 StringThe name of the event.
event ObjectoptionalThe event payload.
Returns:Type Description Boolean true
if a listener was notified
-
Indicates whether there is an event listener on the instance that matches the provided event name.
Parameter:type StringThe name of the event.
Returns:Type Description Boolean Returns true if the class supports the input event.
-
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).
-
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.
-
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.
-
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 FunctionThe 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.
-
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.
-
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: acallback
function and anerrback
function. Thecallback
executes when the instance of the class loads. Theerrback
executes if the instance of the class fails to load.Parameters:callback FunctionoptionalThe function to call when the promise resolves.
errback FunctionoptionalThe 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 });