Creating a apk from jar.

Android studio's ide is based on intelij, they mainly use java as programminglanguage and layout is defined in xml.
I'm not that comfortable in android studio, read as have litle to no experience. I remember that I once during a jQuerry tutorial made an android app from scratch without ever using android studio, it was solely in jQuerry and the I used an guthub project of which I forgot the name, I'm talking about like 6/7y ago, to compile everything to an apk.
Is there a way for me to make my app in springboot, use javaFx as frontend and then compile everything to an apk instead of a jar?
Or is that poor design?

Java FX won't work on an Android device.
It has its own gui framework.

Based on JavaFxPorts and the kokos sample, you can add JavaFX to an Android project created with Android Studio, and you will be able to run a JavaFX scene inside an Android fragment. If you able to run javaFx in an app created by androidstudio, you should be able to use it in an androidApp that isn't created with android studio too

That sample you linked to has a Gradle build file - you should be able to adapt that to your needs without using Android Studio.

Every program created in android studio has a gradlebuildfile.
I never used gradle, how big are the differences with maven?
Or is that a whole new question?

That is a new question Gradle is the standard way to build apps for Android. If you're serious about Android development, you need to become familiar with Gradle anyway. It is conceptually similar to Maven, what with dependency management and all, but the syntax is different - no more XML.

So no mather what, if I want to create an apk from my jar I have to build my javaproject using gradle?

That being the other standard way of building Android apps besides Android Studio, yes. Doesn't the JavaFxPorts documentation talk about that?

Daniel Demesmaecker wrote:Based on JavaFxPorts and the kokos sample, you can add JavaFX to an Android project created with Android Studio, and you will be able to run a JavaFX scene inside an Android fragment.

Crikey.
You learn something new every day.

You can add JavaFX to an Android project developed with Android Studio using JavaFxPorts and the kokos example, and you'll be able to execute a JavaFX scene within an Android fragment. If you can run javaFx in an android studio app, you should be able to use it in an android app that wasn't developed using android studio as well.