Question

I have been trying to implement the API for the serial port found the the below web page. I am a beginner in all this and I am sure about what I am looking at:

http://code.google.com/p/android-serialport-api/source/browse/#svn%2Ftrunk%2Fandroid-serialport-api%2Fproject%2Fjni

Questions:

1) The .c files are built how? Do I need to download the NDK? I assume the .c file is run directly by the virtual machine, or what? Or is the executable for the .c the file in the libs directory? If so, how do I utilize the libserial_por.so file?

Thanks!

Answer 1

The .c files are built into a library by running ndk-build in the project directory. You need the NDK.

The .c files are not run directly by the virtual machine, but rather a library is created in the libs directory, which is then loaded along with the SerialPort class.

To use the library, just use the SerialPort class which already has bindings to the library.

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C files will be compiled to an ARM binary library with the extension .so by the NDK. Take a look at the NDK Documentation, section “Getting Started with the NDK”, to find out how to use it.

Basically, you place your .c files in the jni directory, change Android.mk to specify how to compile them, then run ndk-build to build the library. The resulting lib<name>.so will be placed in the lib directory. You then use your library in the Java project with System.loadLibrary('<name>').

This of course means the library must have a JNI interface for you to be able to use with the Java application, since Android doesn’t support JNA yet.

I see though that the code you pointed out is an Android project. To run it, simply run ndk-build in the project directory to build the library, then run the project in an emulator.