How to use external native library in Android

Question

I am trying to learn NDK, and I'd like to use external library (libopus). After reading some articles, I got these steps:

git clone https://android.googlesource.com/platform/external/libopus
mv libopus jni
NDK_PROJECT_PATH=. ndk-build

It crated libs/armeabi/libopus.so file. Yay, awesome! ... And now what? How can I use this library? How can I call its functions and methods?

Also, will my app run on non-ARM architectures (x86, MIPS), because armeabi suggests it'll be ARM only.

github.com/tbocek/opus-wrapper libopus is a pretty complex place to startup with ndk because at the interface level you also have to dive into media streams and thread handlers for those streams along with the pointers/references to functions operating on the media streams. — Robert Rowntree
– Robert Rowntree, Commented Feb 5, 2015 at 15:45

Robert · Accepted Answer · 2015-02-05 15:32:10Z

1

You can not just use standard Linux libraries. Java/Android uses the Java Native Interface (JNI) which is special C code that builds the bridge between Java part and native part.

It looks like you already have NDK installed. Look into the project samples, e.g. the "hello-jni" project. In this example you can see what JNI C code you have to write and how to access the self written functions from within your Java code.

Regarding the architectures: Yes, an ARM library is for the ARM platform only. If you want to create a cross-platform App you have to compile all native libraries for each supported platform (usually ARM, ARMv7, x86 and MIPS).

answered Feb 5, 2015 at 15:32

Robert

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2 Comments

Pitel Over a year ago

So I'll have to write some additional wrapper in C which will enable opus functions to Java?

Robert Over a year ago

If there is not already an existing wrapper or a "Java binding" sub-project of the library you want to use, yes.

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