Calling into Swift code from Android

[sgade]

First of all, thank you for all the open-source repositories in relation to Swift-on-Android. They provide great value for anyone interested! 🚀

I have a question on how to get it running within Android Studio/Gradle. I have followed your installation guide and completed my setup according to the gradle plugin documentation. I also looked at the example repo which cleared a lot of things up for me, or rather showed me how to implement them.

I do not understand everything that is going on until this point, however, my main issue is that I can now compile my Swift sources with the appropriate gradle task but I cannot call into them from Android. I'm calling from Kotlin if that matters.

How do I get the Android app to know the package that was generated from my Swift source files?
Help is very much appreciated! 🙂

[andriydruk]

Hi,

Unfortunately, our current build tools can't generate Kotlin's headers for your Swift code automatically. That's why you need to write it manually with appropriate annotations. Please check swift-android-architecture Java headers
After you mark classes with annotations our annotation processor will generate all JNI code for you and after that, you can call Swift code from Java/Kotlin.

In our sample swift-android-architecture we use Java. But there is new Swift Weather App that already use Kotlin as a primary language.

[sgade]

Alright, thanks for your reply! Now I understand why there is a need to write the Java/Kotlin headers. In my understanding until now, I thought that those were also generated automatically from the Swift sources.

So once there are those headers in place, will the gradle plugin handle the rest or is there any other step involved?

I'd really like for a general overview of the architecture and the workflow with it to exist, as there is quite some mental load required with getting to know it. If you have time for it it would be a great addition to the toolchain.