extent

Calculates and returns the extent of the GraphicsOverlay.graphics collection. The extent's com.arcgismaps.geometry.SpatialReference is that of the GeoView that contains the overlay. If the overlay is not in a view, returns null. If the overlay is in a view but that view does not yet have a spatial reference, returns null. If the overlay is in a view with a spatial reference, but has no graphics, then an empty envelope will be returned.