Could you try:

env->CallVoidMethod(obj, method, modelviewArray);

instead of:

env->CallObjectMethod(obj, method, modelviewArray);

Not sure if that'll make a whole lot of difference...

Rob.

Can you post the code that you're using?

Where are you seeing the null value? - on the C++ or Java side?

hey kim ,i followed the steps in your reply to do what calibronbon is trying to do but modelviewArray returns null value,i tried many things but got no clue why this is happening,plz help me for this

Use JNI calls to pass up the array. For example:

ImageTargetsRenderer.java

public void updateModelviewMatrix(float modelviewArray[])
{
    // do something with the array
}

ImageTargets.cpp

Java_com_qualcomm_QCARSamples_ImageTargets_ImageTargetsRenderer_renderFrame(JNIEnv *env, jobject obj)
{
...
    jclass javaClass = env->GetObjectClass(obj);
    jfloatArray modelviewArray = env->NewFloatArray(16);
    env->SetFloatArrayRegion(modelviewArray, 0, 16, modelViewMatrix.data);
    jmethodID method = env->GetMethodID(javaClass, "updateModelviewMatrix", "([F)V");
    env->CallObjectMethod(obj, method, modelviewArray);
    env->DeleteLocalRef(modelviewArray);
...
}

- Kim