This project demonstrates how to integrate SWIG (Simplified Wrapper and Interface Generator) into the Android project. In this example, SWIG wraps native C code according to an interface file and generates the proxy classes needed to call native functions from Java/Kotlin.
- Generalizes (through interface files) writing wrapper code and takes care of a lot of boilerplate when it comes to working with JNI directly.
- Callbacks to Java still need to be hand written. If somebody else figures out how to write callbacks to Java using the interface files to modify the proxy classes, by all means do a pull request :)
(If interested in how to register callbacks to Java from Native C check out Android JNI Examples which I also wrote!
In order to integrate SWIG with the gradle's build process, a custom task was used to call a shell script
called jni-build.sh. The script uses SWIG to generate the Java proxy classes used to interface with the C source code.
The script is located at app/src/main/java
NOTE: On first build of the project, the jni-build.sh script will generate a file app/src/main/java/swig_tool_config.txt
which requires the user to specify the location of where the SWIG executable is located. For example, if my SWIG tool is located in my local bin directory, the swig_tool_config.txt should contain one line: /usr/local/bin/swig
Unit testing of the native methods is solely instrumented since loading of the native libraries without instrumentation requires additional configurations that, for the sake of brevity, isnt worth it.