FeatureLayer class final

A layer that can visualize feature data.

Feature layers can display Feature data from a range of online feature table sources, such as ServiceFeatureTable, WfsFeatureTable or OgcFeatureCollectionTable source, and offline sources such as GeodatabaseFeatureTable, ShapefileFeatureTable, or GeoPackageFeatureTable. You can construct a feature layer object using these feature table sources or you can obtain it directly from a map or scene's collection of GeoModel.operationalLayers.

Feature layers can also be used to store features associated with a utility network. To display features in a FeatureCollectionTable, use FeatureCollectionLayer instead.

Feature layers can be used to display, select, and query features in a layer. Individual features can be queried and filtered based on spatial queries or SQL queries. String comparisons for features queried in service feature tables are case insensitive.

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.

The features in a feature layer 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 ServiceFeatureTable. 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 synchronized back to the server.
• Geodatabase - backed by a GeodatabaseFeatureTable. 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 GeodatabaseSyncTask to synchronize the geodatabase with the service. The geodatabase can also be a mobile geodatabase created by ArcGIS Pro. These geodatabases cannot be synced and use a default renderer.
• Shapefile - backed by a ShapefileFeatureTable. Use a feature layer to show the contents of a shapefile (.shp).
• Geopackage - backed by a GeoPackageFeatureTable. This uses a feature layer to render the tables in a GeoPackage (.gpkg). A GeoPackage is a data source that conforms to the OGC GeoPackage specification. Geopackage feature tables can be edited and saved, but do not 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 WfsFeatureTable. 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 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.axisOrder and WfsFeatureTable.filterAxisOrder.
• OGC API Features - Backed by an OgcFeatureCollectionTable. 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 and OGC API - Features - Part 2.

The features displayed in a FeatureLayer are automatically projected to match the map or scene's GeoModel.spatialReference, if necessary. Local tables cannot be projected automatically.

FeatureLayer does not expose every value defined in the web map or web scene specification. You can obtain a dictionary of unsupported values from FeatureLayer.unsupportedJSON. The FeatureLayer also provides FeatureLayer.unknownJSON to return JSON that is not recognized in the web map or web scene specification. Performance characteristics

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

Initially, a local cache must be created. 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. You can eliminate the network usage by provisioning the cache directly to the device in advance.

If the feature layer's FeatureTable is backed by a service it has three feature request modes (FeatureRequestMode) that control 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 are manually populated using a call to ServiceFeatureTable.populateFromService. Once populated, all queries are made against the local table only. ServiceFeatureTable.populateFromService 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.