pkgs/jnigen/example/in_app_java/README.md

# In-App Java Example

This example shows how to write custom java code in `android/app/src` and call
it using bindings generated by `jnigen`.

### How to run this example:

- Run `flutter run` to run the app.

- To regenerate bindings after changing Java code, run
  `dart run tool/jnigen.dart`. This requires at least one APK build to have
  been run before, so that  `jnigen` can obtain classpaths of Android Gradle
  libraries. Therefore, run `flutter build apk` once before generating bindings
  for the first time, or after a `flutter clean`.

### General steps

These are general steps to integrate Java code into a Flutter project using
`jnigen`.

- Place Java code in a suitable package folder under the `android/` subproject
  of the flutter app.
- Create a `jnigen` configuration script like `tool/jnigen.dart` in this
  example.
- Generate bindings by running that script with `dart run`.
- To prevent tree shaking of your custom classes (which are always accessed
  reflectively in JNI) use either the `@Keep` annotation 
  (`androidx.annotation.Keep`) for code written in the application itself, or
  a [proguard-rules file](https://github.com/dart-lang/native/blob/main/pkgs/jnigen/example/in_app_java/android/app/proguard-rules.pro)
  for external libraries.
- Build and run the app.