`manganis::ffi` not working in minimal example

[CAPage]

Problem

manganis::ffi is not working in a minimal example of its use (https://github.com/CAPage/minimal-ffi-repro) - receiving the error:

JNI DETECTED ERROR IN APPLICATION: JNI FindClass called with pending exception java.lang.ClassNotFoundException: Didn't find class "com.example.minimalffirepro.MinimalFFIReproAndroid" on path: DexPathList[[directory "."],nativeLibraryDirectories=[/system/lib64, /system_ext/lib64, /system/lib64, /system_ext/lib64]]

I investigated a number of problems, including checking whether or not the class is actually present in the APK (it is, I checked with Android studio.) I also attempted to manually load the class with both find_class and load_class_with_classloader, neither of which were able to load the class.

Steps To Reproduce

Set up a new Dioxus project, add a simple Kotlin class to src/main/kotlin and the corresponding manganis::ffi extern "Kotlin" block in your main.rs. Attempt to call a method of the Kotlin class from Rust. Or, take a look at my minimal reproduction (https://github.com/CAPage/minimal-ffi-repro).

Expected behavior

The object should be created and the method should be callable.

Environment:

• Dioxus version: 0.8.0-alpha.0 (also tried with 0.7.9)
• Rust version: 1.98.0-nightly
• OS info: MacOS 15.7.7
• App platform: Android. (Pixel 10/Android 16.0, emulated through Android Studio.)

Questionnaire

I have actually managed to get this working using a patched version of Dioxus (and I’m willing to work on this to fix it), but I don’t have a lot of context for manganis or the approach taken, outside of my own investigation - so would love to know if this is the right approach/a known issue/etc before moving forward!

Given that the issue seemed to be about which classloader was used (e.g. not a classloader that has access to the APK), including when load_class_with_classloader was called, my patch involved:

• Modifying load_class_with_classloader such that it takes an activity parameter, gets the classloader of the activity (getClassLoader()), and then uses loadClass to load the target class.
• Modifying the manganis::ffi macro such that it uses load_class_with_classloader rather than find_class .

When using this patched version of Dioxus, the minimal reproduction (https://github.com/CAPage/minimal-ffi-repro) works perfectly - both through manganis::ffi and when loaded manually through load_class_with_classloader .