| ## jnigen examples |
| |
| This directory contains examples on how to use jnigen. |
| |
| | Directory | Description | |
| | ------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------- | |
| | [in_app_java](https://github.com/dart-lang/native/tree/main/pkgs/jnigen/example/in_app_java/) | Demonstrates how to include custom Java code in Flutter application and call that using jnigen | |
| | [pdfbox_plugin](https://github.com/dart-lang/native/tree/main/pkgs/jnigen/example/pdfbox_plugin/) | Example of a flutter plugin which provides bindings to Apache PDFBox library. Currently works on Flutter desktop and Dart standalone on linux. | |
| | [notification_plugin](https://github.com/dart-lang/native/tree/main/pkgs/jnigen/example/notification_plugin/) | Example of a reusable Flutter plugin with custom Java code which uses Android libraries. | |
| | [kotlin_plugin](https://github.com/dart-lang/native/tree/main/pkgs/jnigen/example/kotlin_plugin) | Example of using jnigen to generate bindings for Kotlin. | |
| |
| We intend to cover few more use cases in future. |
| |
| ## Creating a jnigen-based plugin from scratch |
| |
| ### Dart package (Standalone only) |
| |
| - Create dart package, add `jni` as dependency and `jnigen` as dev dependency. |
| - Write the jnigen config similar to [the one in pdfbox_plugin](https://github.com/dart-lang/native/tree/main/pkgs/jnigen/example/pdfbox_plugin/jnigen.yaml). |
| - Generate JNI bindings by running `dart run jnigen --config jnigen.yaml`. |
| |
| - In the CLI project which uses this package, add this package, and `jni` as a dependency. |
| - Run `dart run jni:setup` to build native libraries for JNI base library and jnigen generated package. |
| - Import the package. See [pdf_info.dart](https://github.com/dart-lang/native/tree/main/pkgs/jnigen/example/pdfbox_plugin/dart_example/bin/pdf_info.dart) for an example of using JNI from dart standalone. |
| |
| ### Flutter FFI plugin |
| |
| Flutter FFI plugin has the advantage of bundling the required native libraries along with Android / Linux Desktop app. |
| |
| To create an FFI plugin with JNI bindings: |
| |
| - Create a plugin using `plugin_ffi` template. |
| - Remove ffigen-specific files and stubs. |
| - Follow the above steps to generate JNI bindings. The plugin can be used from a flutter project. |
| |
| - It may be desirable to generate the bindings into a private directory (Eg: `lib/src/third_party`) and re-export the classes from the top level dart file. |
| |
| - To use the plugin from Dart projects as well, comment-out or remove flutter SDK requirements from the pubspec. This is however problematic if you want to publish the package. |
| |
| ### Android plugin with custom Java code |
| |
| - Create an FFI plugin with Android as the only platform. |
| - Build the example/ Android project using command `flutter build apk`. After a release build is done, jnigen can use a gradle stub to collect compile classpaths. |
| - Write your custom Java code in `android/src/main/java` hierarchy of the plugin. |
| - Generate JNI bindings as described above. See [notification_plugin/jnigen.yaml](https://github.com/dart-lang/native/tree/main/pkgs/jnigen/example/notification_plugin/jnigen.yaml) for example configuration. |
| |
| ### Pure dart bindings |
| |
| With Pure dart bindings PoC, most of the FFI setup steps are not required. For example, a simple flutter package can be created instead of an FFI plugin, since there are no native artifacts to bundle. |
| |
| The generated bindings still depend on `package:jni`, therefore running `dart run jni:setup` is still a requirement on standalone target. |
