OpenLayers v4.0.1 API - Class: Layer

# Class: Layer

This documentation is for OpenLayers v4.0.1. The latest is v.

## ol.layer.Layer

Abstract base class; normally only used for creating subclasses and not instantiated in apps. A visual representation of raster or vector map data. Layers group together those properties that pertain to how the data is to be displayed, irrespective of the source of that data.

Layers are usually added to a map with `ol.Map#addLayer`. Components like `ol.interaction.Select` use unmanaged layers internally. These unmanaged layers are associated with the map using `ol.layer.Layer#setMap` instead.

A generic `change` event is fired when the state of the source changes.

#### new ol.layer.Layer(options)

src/ol/layer/layer.js, line 36

  Name | Type | Description
  --- | --- | ---

  `options`

  Layer options.

  Name | Type | Description
  --- | --- | ---
  `opacity` | number | undefined | Opacity (0, 1). Default is `1`.
  `source` | ol.source.Source | undefined | Source for this layer. If not provided to the constructor, the source can be set by calling `layer.setSource(source)` after construction.
  `visible` | boolean | undefined | Visibility. Default is `true` (visible).
  `extent` | ol.Extent | undefined | The bounding extent for layer rendering. The layer will not be rendered outside of this extent.
  `zIndex` | number | undefined | The z-index for layer rendering. At rendering time, the layers will be ordered, first by Z-index and then by position. The default Z-index is 0.
  `minResolution` | number | undefined | The minimum resolution (inclusive) at which this layer will be visible.
  `maxResolution` | number | undefined | The maximum resolution (exclusive) below which this layer will be visible.

  ##### Fires:

  - `change` (ol.events.Event) - Generic change event. Triggered when the revision counter is increased.
  - `change:extent` (ol.Object.Event)
  - `change:maxResolution` (ol.Object.Event)
  - `change:minResolution` (ol.Object.Event)
  - `change:opacity` (ol.Object.Event)
  - `change:source` (ol.Object.Event)
  - `change:visible` (ol.Object.Event)
  - `change:zIndex` (ol.Object.Event)
  - `postcompose` (ol.render.Event)
  - `precompose` (ol.render.Event)
  - `propertychange` (ol.Object.Event) - Triggered when a property is changed.
  - `render` (ol.render.Event)

### Subclasses

- ol.layer.Image
- ol.layer.Tile
- ol.layer.Vector

### Extends

- ol.layer.Base

### Observable Properties

Name | Type | Settable | ol.Object.Event type | Description
--- | --- | --- | --- | ---
`extent` | ol.Extent | undefined | yes | `change:extent` | The layer extent.
`maxResolution` | number | yes | `change:maxresolution` | The maximum resolution of the layer.
`minResolution` | number | yes | `change:minresolution` | The minimum resolution of the layer.
`opacity` | number | yes | `change:opacity` | The opacity of the layer.
`source` | ol.source.Source | yes | `change:source` | The layer source (or `null` if not yet set).
`visible` | boolean | yes | `change:visible` | The visibility of the layer.
`zIndex` | number | yes | `change:zindex` | The Z-index of the layer.

### Methods

#### changed() inherited

src/ol/observable.js, line 58

  Increases the revision counter and dispatches a 'change' event.

#### dispatchEvent(event) inherited

src/ol/observable.js, line 75

  Dispatches an event and calls all listeners listening for events of this type. The event parameter can either be a string or an Object with a `type` property.

  Name | Type | Description
  --- | --- | ---
  `event` | Object | ol.events.Event | string | Event object.

#### get(key){*} inherited

src/ol/object.js, line 101

  Gets a value.

  Name | Type | Description
  --- | --- | ---
  `key` | string | Key name.

  ##### Returns:

  Value.

#### getExtent(){ol.Extent|undefined} inherited

src/ol/layer/base.js, line 108

  Return the `extent` of the layer or `undefined` if it will be visible regardless of extent.

  ##### Returns:

  The layer extent.

#### getKeys(){Array.<string>} inherited

src/ol/object.js, line 115

  Get a list of object property names.

  ##### Returns:

  List of property names.

#### getMaxResolution(){number} inherited

src/ol/layer/base.js, line 120

  Return the maximum resolution of the layer.

  ##### Returns:

  The maximum resolution of the layer.

#### getMinResolution(){number} inherited

src/ol/layer/base.js, line 132

  Return the minimum resolution of the layer.

  ##### Returns:

  The minimum resolution of the layer.

#### getOpacity(){number} inherited

src/ol/layer/base.js, line 144

  Return the opacity of the layer (between 0 and 1).

  ##### Returns:

  The opacity of the layer.

#### getProperties(){Object.<string, *>} inherited

src/ol/object.js, line 125

  Get an object of all property names and values.

  ##### Returns:

  Object.

#### getRevision(){number} inherited

src/ol/observable.js, line 84

  Get the version number for this object. Each time the object is modified, its version number will be incremented.

  ##### Returns:

  Revision.

#### getSource(){ol.source.Source}

src/ol/layer/layer.js, line 115

  Get the layer source.

  ##### Returns:

  The layer source (or `null` if not yet set).

#### getVisible(){boolean} inherited

src/ol/layer/base.js, line 162

  Return the visibility of the layer (`true` or `false`).

  ##### Returns:

  The visibility of the layer.

#### getZIndex(){number} inherited

src/ol/layer/base.js, line 174

  Return the Z-index of the layer, which is used to order layers before rendering. The default Z-index is 0.

  ##### Returns:

  The Z-index of the layer.

#### on(type, listener, opt_this){ol.EventsKey|Array.<ol.EventsKey>} inherited

src/ol/observable.js, line 99

  Listen for a certain type of event.

  Name | Type | Description
  --- | --- | ---
  `type` | string | Array.<string> | The event type or array of event types.
  `listener` | function | The listener function.
  `this` | Object | The object to use as `this` in `listener`.

  ##### Returns:

  Unique key for the listener. If called with an array of event types as the first argument, the return will be an array of keys.

#### once(type, listener, opt_this){ol.EventsKey|Array.<ol.EventsKey>} inherited

src/ol/observable.js, line 124

  Listen once for a certain type of event.

  Name | Type | Description
  --- | --- | ---
  `type` | string | Array.<string> | The event type or array of event types.
  `listener` | function | The listener function.
  `this` | Object | The object to use as `this` in `listener`.

  ##### Returns:

  Unique key for the listener. If called with an array of event types as the first argument, the return will be an array of keys.

#### set(key, value, opt_silent) inherited

src/ol/object.js, line 150

  Sets a value.

  Name | Type | Description
  --- | --- | ---
  `key` | string | Key name.
  `value` | * | Value.
  `silent` | boolean | Update without triggering an event.

#### setExtent(extent) inherited

src/ol/layer/base.js, line 186

  Set the extent at which the layer is visible. If `undefined`, the layer will be visible at all extents.

  Name | Type | Description
  --- | --- | ---
  `extent` | ol.Extent | undefined | The extent of the layer.

#### setMap(map)

src/ol/layer/layer.js, line 167

  Sets the layer to be rendered on top of other layers on a map. The map will not manage this layer in its layers collection, and the callback in `ol.Map#forEachLayerAtPixel` will receive `null` as layer. This is useful for temporary layers. To remove an unmanaged layer from the map, use `#setMap(null)`.

  To add the layer to a map and have it managed by the map, use `ol.Map#addLayer` instead.

  Name | Type | Description
  --- | --- | ---
  `map` | ol.Map | Map.

#### setMaxResolution(maxResolution) inherited

src/ol/layer/base.js, line 197

  Set the maximum resolution at which the layer is visible.

  Name | Type | Description
  --- | --- | ---
  `maxResolution` | number | The maximum resolution of the layer.

#### setMinResolution(minResolution) inherited

src/ol/layer/base.js, line 208

  Set the minimum resolution at which the layer is visible.

  Name | Type | Description
  --- | --- | ---
  `minResolution` | number | The minimum resolution of the layer.

#### setOpacity(opacity) inherited

src/ol/layer/base.js, line 219

  Set the opacity of the layer, allowed values range from 0 to 1.

  Name | Type | Description
  --- | --- | ---
  `opacity` | number | The opacity of the layer.

#### setProperties(values, opt_silent) inherited

src/ol/object.js, line 170

  Sets a collection of key-value pairs. Note that this changes any existing properties and adds new ones (it does not remove any existing properties).

  Name | Type | Description
  --- | --- | ---
  `values` | Object.<string, *> | Values.
  `silent` | boolean | Update without triggering an event.

#### setSource(source)

src/ol/layer/layer.js, line 201

  Set the layer source.

  Name | Type | Description
  --- | --- | ---
  `source` | ol.source.Source | The layer source.

#### setVisible(visible) inherited

src/ol/layer/base.js, line 230

  Set the visibility of the layer (`true` or `false`).

  Name | Type | Description
  --- | --- | ---
  `visible` | boolean | The visibility of the layer.

#### setZIndex(zindex) inherited

src/ol/layer/base.js, line 242

  Set Z-index of the layer, which is used to order layers before rendering. The default Z-index is 0.

  Name | Type | Description
  --- | --- | ---
  `zindex` | number | The z-index of the layer.

#### un(type, listener, opt_this) inherited

src/ol/observable.js, line 147

  Unlisten for a certain type of event.

  Name | Type | Description
  --- | --- | ---
  `type` | string | Array.<string> | The event type or array of event types.
  `listener` | function | The listener function.
  `this` | Object | The object which was used as `this` by the `listener`.

#### unset(key, opt_silent) inherited

src/ol/object.js, line 184

  Unsets a property.

  Name | Type | Description
  --- | --- | ---
  `key` | string | Key name.
  `silent` | boolean | Unset without triggering an event.