I would like to know if the following is possible:
1) create an Android app that accepts some input parameters (args[])
- this app is derived from a c++ GPL library
- it just writes a file to disk according to parameters
-it is GPL licensed too and the source is available
2) make the user install it
3) call it with DexClassLoader from a commercial app, that is, invoke its main with args[] and then just read the file it has produced.

Is GPL fulfilled? Could I do it?

Thank you in advance