I have been experimenting for quite a while with App Inventor 2 from MIT. It is a very simple programming tool and can be used in two ways i.e: Use a single full screen webviewer and set the URL as in webdirect (Webdirect appears as an Android app) or use text boxes, buttons etc and using Filemaker Data Api. Response times are very fast when using App inventor building blocks and Data Api. One can also make use of extensions and perhaps this is an area for some smart Filemaker guys with Java knowledge to create new Filemaker function blocks for App Inventor and thereby helping (or selling to) the community at large. ‘Most native Android functionality' is standard ie. camera, barcode, sensors etc. and by using Data Api all info can be transferred/stored in Filemaker Server.
The app created in App Inventor can be uploaded to the Playstore although have not tried this myself yet. App Inventor 2 is free of charge. There numerous websites with examples i.e https://puravidaapps.com/
Given the absence of any other easy tool instead of Android Studio with 1,000+ files (slightly exaggerated but you get the idea) to support a simple 'Hello world' sample then App Inventor 2 may be your answer!