Every time our mounts, it fetches map data from the API (3-5s delay). Is there a way to call getMapData() once and pass the result to so it skips the network request on subsequent mounts?
Yes, this would be possible by downloading the MVF (Mappedin Venue Format) file using Mappedin REST APIs and passing that file to the Mappedin SDK to load instead of calling getMapData().
The Offline Mode Guide explains how to load an MVF file this way.
To not be in full offline mode, your app could download the MVF file and store it locally for re-use. I recommend building in some sort of expiry so that the MVF is only kept for a limited period of time, allowing users get map updates. This guide explains how to use Mappedin REST APIs to download the MVF file: Downloading an MVF Using the Mappedin REST API