How to fix my 2d array code that will be transfer to java uses JNI?

Question

i have trying to pass array from c++ to java. no error in compilation. but failed to run (crash). when i debug the code, error occurs in return code

i try to implement this code how to return c++ char 2d array using JNI to JAVA

here is my code

    JNIEXPORT jobjectArray JNICALL my_function();

    // ...
    // some code
    // ...

    // i want convert float point[3][2] to java

    jclass intArray1DClass = env->FindClass("[I");
    jclass intArray2DClass = env->FindClass("[[I");

     //  float point[3][2]
     jint sizeX = 3;
     jint sizeY = 2;


    jobjectArray array2D = env->NewObjectArray(
                sizeX, intArray2DClass, NULL);

    for (jint i = 0; i < sizeX; i++)
    {
        jobjectArray array1D = env->NewObjectArray(
                    sizeY, intArray1DClass, NULL);

        for (jint y = 0; y < sizeY; y++)
        {
            jfloatArray value = env->NewFloatArray(point[i][y]); // float point[3][2]
            env->SetObjectArrayElement(array1D, y, value);
        }

        env->SetObjectArrayElement(array1D, i, array1D);
    }

    return array2D;

and this is how i call function from java. is it right?

     float[][] point = my_function()

thank you

Update

Finally i use 1D array because its simple to write the code. and according to 1D or 2D array, what's faster? , we should use 1D array

     jint sizeX = 6;

     jfloatArray array1D = env->NewFloatArray(sizeX);

     env->SetFloatArrayRegion(array1D, 0, sizeX, point);


     return array1D;

sklott · Answer 1 · 2019-07-11T07:32:18.523

First, it looks like you declaring Java array of ints, i.e. int [][], not float[][].

Second, why you set jfloatArray as element of your array? It should be simple float.

Third, in last line you probably meant env->SetObjectArrayElement(array2D, i, array1D);

Fourth, when you declaring array you need to specify class which it contains, so for 2D array it contains 1D array and for 1D array it contains just floats.

PS: Linked question/answer is actually returning 3D array. So you need to reduce number of dimensions in you code.

How to fix my 2d array code that will be transfer to java uses JNI?

1 Answers1