Unable to link native library in OpenCV Android sample

Question

I have OpenCV code (c++), which I want to use in Android. To do this I have to use Android NDK. I downloaded OpenCV package for Android development (ver. 2.4.0) and did all

Answer 1

Instead of loading your native library as

static{
    System.loadLibrary("YOUR_LIBRARY");
}

load your library after opencv manager is connected in "onManagerConnected" method in you "BaseLoaderCallBack". Following is my code snippet working for me

public void onManagerConnected(int status) {
                switch(status){
                case LoaderCallbackInterface.SUCCESS:
                    Toast.makeText(getApplicationContext(), "manager connected", Toast.LENGTH_LONG).show();
                    System.loadLibrary("MYNATIVELIB");
                    break;
                default:
                    super.onManagerConnected(status);
                    break;
                }
            }

Answer 2

You're at a higher level than the actual problem. See "Getting started with the NDK", when you run

    cd <project>
    <ndk>/ndk-build

... what does it say? (Remember to use the cygwin window and not a dos prompt).

Answer 3

Whoohoo!

Finally I found solution for this problem by myself!

I decided to debug line:

System.loadLibrary("native_sample");

To do this I downloaded android source code from Android-SDK and then attached source folder (/opt/android-sdk-linux/sources/android-15) to my project. After this I found that error was:

Cannot load library: link_image[1936]:    37 could not load needed library 'libopencv_java.so' for 'libhello-jni.so' (load_library[1091]: Library 'libopencv_java.so' not found)

And really this library is not in lib directory. I don't know why but ndk-build ignored it. So i decided to copy and load it manualy. For this I copied libopencv_java.so from /opt/OpenCV-2.4.0/libs/armeabi-v7a and also edited java code:

static {
    System.loadLibrary("opencv_java"); //load opencv_java lib
    System.loadLibrary("native_sample");
}

Actually similar problems are:

1. Can not load Opencv libraries in necessitas
2. Android OpenCV: cannot dlopen camera wrapper library

From second solution I found that I can load libraries using dlopen, but I haven't tried it yet.

So I will write simple bash-script that will do it (just copy) for myself.

Thanks to all.