new module:BackgroundLayerMgr(ngeoLayerHelper)
Provides a service for setting/unsetting background layers in maps.
The notion of background/base layers doesn't exist in OpenLayers. This service adds that notion.
Setting a background layer to map is done with the set
function:
ngeoBackgroundLayerMgr.set(map, layer);
To unset the background layer pass null
as the layer
argument:
ngeoBackgroundLayerMgr.set(map, null);
The get
function returns the current background layer of the map passed
as an argument. null
is returned if the map doesn't have a background
layer.
The background layer is always added at index 0 in the map's layers collection. When a background layer is set it is inserted (at index 0) if the map does not already have a background layer, otherwise the new background layer replaces the previous one at index 0.
Users can subscribe to a 'change' event to get notified when the background layer changes:
ngeoBackgroundLayerMgr.on('change', function(e) {
// do something with the layer
let layer = ngeoBackgroundLayerMgr.get();
// know which layer was used before
let previous = e.previous
});
See our live examples: ../examples/backgroundlayer.html ../examples/backgroundlayerdropdown.html
Parameters:
Name | Type | Description |
---|---|---|
ngeoLayerHelper |
ngeo.map.LayerHelper | Themes service. |
Extends
- ol.Observable