Thanks for taking interest in GroupDocs.Viewer for Java 3.x and posting your concerns.
Please note, there is a possibility that some of the API classes (current versions of the API) are not supported in android. We do have a plan to provide a complete API for android but we cannot share any ETA at the moment.
However, we are in contact with the concerned team, as we get any update from them, we’ll apprise you.
Have a nice weekend ahead.