JNI Utils

using this library:

implementation("io.github.landrynorris:jni-utils:0.0.1-alpha01")

This library provides bindings to the JNI library on Android.

The primary motivator of this library is the syntax for calling a method on JNIEnvVar

env.pointed.pointed?.SetObjectField?.invoke(env, fieldId, value)

This library allows you to write

env.setObjectField(fieldId, value)

Or take for example, converting a Kotlin String to a jstring:

//Raw JNI library
memScoped {
    env.pointed.pointed?.newString?.invoke(myString.wcstr.ptr, length)
}

//This library
myString.toJString(env)

Registering natives

This library provides a DSL for registering JNI methods.

env.registerNatives {
    clazz = env.findClass("io.github.landrynorris.sample.JniBridge".signature())

    method("buttonClicked") {
        signature = signature(::buttonClicked)
        function = staticCFunction(::buttonClicked)
    }

    method("getText") {
        signature = Signature(listOf(Long), String).toString()
        function = staticCFunction(::getText)
    }
}

You must provide a clazz value in the DSL.

There are two ways of defining the signature:

1. the Signature() constructor. Provide a list of parameter signatures and a single return signature. The Signature#toString() method creates a signature that the JNI can recognize.
2. For simple methods (jstring, jobject, etc. are not currently supported), you can use the signature(Function) method to automatically create a signature.