Apache POI [ https://poi.apache.org/ ]
[https://mvnrepository.com/artifact/org.apache.poi/poi/4.1.1]
can be used in the android app. Multidex is needed.
But originally the library works well only with xls files.
To work with xlsx the Apache POI-ooxml is needed.
[https://mvnrepository.com/artifact/org.apache.poi/poi-ooxml/4.1.1]
Also there is [https://github.com/andruhon/android5xlsx]
There is a issue with java.awt
also [https://github.com/dhatim/fastexcel]
Creating Excel files with C and libxlsxwriter
[https://libxlsxwriter.github.io/index.html]