FeatureLayer

A layer that can visualize vector/feature data. Feature layers display feature data from an online ServiceFeatureTable source, or from offline sources such as GeodatabaseFeatureTable, ShapefileFeatureTable, or GeoPackageFeatureTable. Feature layers can be used to display, select, and query features in a layer. If the underlying feature service or table supports editing, you can use it with a feature layer as a basis for editing geometry, attributes, and attachments. Feature layers can also be used to store features associated with a utility network.

To display features in a FeatureCollectionTable, use FeatureCollectionLayer instead.

Features are retrieved as needed by the app. Features can be downloaded from a sync-enabled feature service when the device is connected and cached locally for use when the device is offline. Edits can then be synchronized back to the service.

Functional characteristics

The following sources can be rendered using a feature layer:

• Feature service - backed by a feature service table. The feature data from the service is cached locally in the table. New features are retrieved automatically when you navigate the map. The local table cache is discarded when the layer is disposed. If sync is enabled, features can be created, edited, and pushed to the server.

• Geodatabase - backed by a geodatabase feature table. The geodatabase can be a replica of a feature service, which allows synchronizing with the feature service, or taking the content of a feature service offline. Use a geodatabase sync task to synchronize the geodatabase with the service. The geodatabase can also be a mobile geodatabase created by ArcGIS Pro. Mobile geodatabases cannot be synced and use a default renderer.

• Shapefile - backed by a shapefile feature table. Uses a feature layer to show the contents of shapefiles (.shp).

• Geopackage - backed by a geopackage feature table. This uses a feature layer to render the tables in a GeoPackage (.gpkg). A GeoPackage is a data source that conforms to the https://www.ogc.org/standards/geopackage. Geopackage feature tables can be edited and saved, but can't support sync, because there is no backing feature service. This API supports GeoPackage versions 1.0, 1.1, and 1.2.

• Web Feature Service (WFS) - backed by a WFS feature table. You can populate the table using QueryParameters or raw XML-encoded GetFeature queries. A WFS feature table only supports the manual cache feature request mode. This API supports OGC WFS[https://www.ogc.org/standards/wfs] versions 2.0.0 and 2.0.2. WFS server implementations are inconsistent in how they expect coordinates to be formatted. Some return and expect coordinates in (x,y) order, while others expect (y,x). This API anticipates the order but you can configure it with the WfsFeatureTable.getAxisOrder() and WfsFeatureTable.getFilterAxisOrder().

• OGC API Features - Backed by an OGC feature collection table. You can populate the table using QueryParameters. An OCG feature collection table only supports the manual cache feature request mode. This API supports OGC API - Features - Part 1[https://docs.opengeospatial.org/is/17-069r3/17-069r3.html] and https://docs.opengeospatial.org/is/18-058/18-058.html.

Individual features can be queried and filtered based on spatial queries or SQL queries. Introduced at 100.3.0, string comparisons for features queried in service feature tables are case insensitive.

The features displayed in a FeatureLayer are reprojected to match the GeoModel.getSpatialReference(), if necessary. Local tables cannot be reprojected automatically.

The FeatureLayer does not expose every value defined in the web map specification. You can obtain a dictionary of these unsupported values from FeatureLayer.getUnsupportedJson(). The FeatureLayer also provides FeatureLayer.getUnknownJson() to return JSON that was not recognized in the web map specification.

Performance characteristics

Because full feature information is cached locally in a geodatabase, shapefile, or GeoPackage, and features are drawn natively, this layer type offers excellent display performance when zooming and panning the map within the extent of cached features. Querying features is also efficient, enabling app functions such as real-time updates of query results in a map.

The local cache must be initially created, which can be resource-intensive for the server. The initial download to the device may require extensive network usage and subsequent local device storage. App memory usage increases with the number and complexity of the features cached. Network usage can be eliminated by provisioning the cache directly to the device in advance.

Feature tables backed by a service define three feature request modes. The table's feature request mode controls how and when features are requested from the service:

• On interaction cache - Features are requested automatically for the visible map or scene extent. As the user pans and zooms, features are cached locally. If the user returns to an area where features have already been loaded, the table won't need to download those features again.

• Manual cache - Features must be manually populated using a call to ServiceFeatureTable.populateFromService(QueryParameters, Boolean, MutableListImpl). Once populated, all queries are made against the local table only. ServiceFeatureTable.populateFromService(QueryParameters, Boolean, MutableListImpl) can be called again to retrieve more features from the service.

• On interaction, no cache - Features are requested automatically for the visible map extent. As the user pans and zooms, features outside the visible extent are not cached and must be downloaded again each time.