in_app_java

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 for external libraries.
• Build and run the app.