The Basemap Gallery widget displays a collection of images representing basemaps from your organization or a user-defined set of map or image services. When a new basemap is selected from the Basemap Gallery, the map's basemap layers are removed and replaced with the basemap layers of the associated basemap selected in the gallery.
Configure the Basemap Gallery widget
There is no configuration for the Basemap Gallery widget. It synchronizes with the Basemap Gallery set in your organization.
Use the Basemap Gallery widget
Click the Basemap Gallery widget to display all the basemaps. Click one of the basemap thumbnails to set it as the active basemap for the app.