| [](https://github.com/dart-lang/native/actions/workflows/jnigen.yaml) |
| [](https://coveralls.io/github/dart-lang/native?branch=main) |
| [](https://pub.dev/packages/jni) |
| [](https://pub.dev/packages/jni/publisher) |
| |
| # jni |
| |
| This is a support library to access JNI from Dart / Flutter code. This provides the common infrastructure to bindings generated by [jnigen](https://pub.dev/packages/jnigen), as well as some utility methods. |
| |
| This library contains: |
| |
| * Functions to access the JNIEnv and JavaVM variables from JNI, and wrapper functions to those provided by JNI. JNIEnv is exposed via `GlobalJniEnv` type which provides a thin abstraction over JNIEnv, so that it can be used from multiple threads. |
| * Functions to spawn a JVM on desktop platforms (`Jni.spawn`). |
| * Some Android-specific helpers (get application context and current activity references). |
| * `JObject` class, which provides base class for classes generated by jnigen. |
| * Commonly used Java classes like `JList`, `JMap`, `JInteger`, ... |
| |
| Apart from being the base library for code generated by `jnigen` this can also be used for one-off uses of the JNI and debugging. __To generate type-safe bindings from Java libraries, use `jnigen`.__ |
| |
| ## Documentation |
| The test/ directory contains files with comments explaining the basics of this module, and the example/ directory contains a flutter example which also touches some Android-specifics. |
| |
| Using this library assumes some familiarity with JNI - it's threading model and object references, among other things. |
| |
| ## Migrating to 0.8.0 |
| |
| Check the [changelog](https://github.com/dart-lang/native/blob/main/pkgs/jni/CHANGELOG.md#080-wip). |
| |
| The API for standalone use of `package:jni` (without `package:jnigen`) has |
| changed to use `JClass.forName` for finding classes. Find the methods and fields |
| by accessing them from the retrieved `JClass`. For example find an instance |
| method with a name and a signature using `jClass.instanceMethodId`. Then you can |
| `call` the resulting `JInstanceMethodId` to call the instance method. |
