Hello world jni example for intellij. Use as stub for JNI projects using gradle build system.
Jetbrains' instructions on this were suspiciously simple, and of course did not work out of the box.
I have created this sample with instructions and comments so I do not forget when I ever have to do this again.
I have updated model.components in build.gradle. From terminal, you can now call ./gradlew helloSharedLibrary without errors. Object and Shared Object files will be created in the build directory as follows:
- build/objs/hello/shared/helloC/46gd7i53yh3z9kv2bj1ure0t2/hello.o
- build/libs/hello/shared/libhello.so
(This may differ slightly on Windows)
Attempt to run HelloWorld.java (I have included a 'main' method, so you can run the class file directly by right-clicking on it and selecting run). This will fail at first with an UnsatisfiedLinkError, but it does generate a stub of a build configuration, 'HelloWorld'.
From the Build Configurations dropdown, select edit and add the the following VM option to the new 'HelloWorld' configuration: -Djava.library.path="build/libs/hello/shared".
Apply the changes and dismiss the dialog. You can now run the example. You will see 'Hello from JNI' in the output. Success!
Note that if you edit the C code, you will have to invoke ./gradlew helloSharedLibrary again in order to recompile the shared object. You don't want to rebuild your native libraries automatically every time you edit your java/kotlin code.
I have added a stub test class. Right click to run tests. It will fail at first too.
You will need to edit its build configuration likewise: -Djava.library.path="build/libs/hello/shared"
Note that these instructions do not apply to Android Studio, where the process differs (and is less problematic).
Instructions on NDK integration here, or better still, download the developer samples and play with them.
In fact, by far simplest, from Android Studio, select File -> New -> Import Sample. Type ndk in the filterbox to navigate quickly and select from the many NDK samples. These should run out of the box once you have NDK prepared as shown in the guide first.
NDK (Native Development Kit) is JNI for Android, BTW.