Android, JNI call java constructor in C++

Question

i have following java class:

 public class SHPObject {
    public int nSHPType;
    int nShapeId;
    public int nParts;
    int[] panPartStart;
    int panPartType;
    int nVertices;
    double[] padfX;
    double[] padfY;

    public SHPObject(int nSHPType, int nParts, int[] panPartStart, double[] padfX, double[] padfY ){
        this.nSHPType = nSHPType;
        this.nParts = nParts;
        this.panPartStart = panPartStart;
        this.padfX = padfX;
        this.padfY = padfY;
    }

 }

And i am trying to create object of this class in c++. This is my code for this:

    jclass shpObjectClass = env->FindClass("com/example/kaczor/tmc_shpreader/Shape/Shapes/SHPObject");
    jmethodID shpObjectConstructor = env->GetMethodID(shpObjectClass, "<init>", "(II[I[D[D)V");
    jobject recognition_result;
    SHPObject* a = new SHPObject[nEntities];
    for(i = 0; i < nEntities; i++){
        a[i] = *SHPReadObject(handle,i);
        recognition_result = env->NewObject(
                shpObjectClass, shpObjectConstructor, a[i].nSHPType, a[i].nParts, *a[i].panPartStart, *a[i].padfX, *a[i].padfY);
    ...
    }

Sadly when executing this code my application close. Although when i change my constructor in java, and method signature in c++ to:

public SHPObject(int nSHPType, int nParts, int[] panPartStart)

methodID shpObjectConstructor = env->GetMethodID(shpObjectClass, "<init>", "(II[I)V");

everything work fine. So there is some problem in passing double[] variables. I cant figure out what is wrong. This is part of stack trace after executing this code (not really sure what part of it i should give, i dont notice anything refering to an error):

06-19 17:23:08.876 728-728/com.example.kaczor.tmc_shpreader W/dalvikvm: 
Invalid indirect reference 0xbcad9adc in decodeIndirectRef
06-19 17:23:08.876 728-728/com.example.kaczor.tmc_shpreader E/dalvikvm: VM 
aborting
06-19 17:23:08.906 728-728/com.example.kaczor.tmc_shpreader A/libc: Fatal 
signal 11 (SIGSEGV) at 0xdeadd00d (code=1), thread 728 (r.tmc_shpreader)
[...]

Edit: C++ SHPObject definition can be find at: http://shapelib.maptools.org/shp_api.html

Have you checked if the C native type double is the same size as the JNI defined type jdouble? See: docs.oracle.com/javase/8/docs/technotes/guides/jni/spec/… — Richard Critten
– Richard Critten, Commented Jun 19, 2017 at 17:35

Pan Wolodyjowsky · Accepted Answer · 2017-06-19 23:13:26Z

So i've converted double[] to jdoubleArray, not sure why i didn't have to convert int[]. Although i found out that all values of int[] in Java were 0, so i have to convert it anyway.

    jclass shpObjectClass = env->FindClass("com/example/kaczor/tmc_shpreader/Shape/Shapes/SHPObject");
    jmethodID shpObjectConstructor = env->GetMethodID(shpObjectClass, "<init>", "(IIIIIII[I[D[D)V");
    SHPObject* a = new SHPObject[nEntities];
    jobject recognition_result;
    jobjectArray shapesToReturn = env->NewObjectArray(nEntities,shpObjectClass,env->NewObject(shpObjectClass,defaultShpObjectConstructor));

    for(i = 0; i < nEntities; i++){
        a[i] = *SHPReadObject(handle,i);

        jdoubleArray padfXARRAY = env->NewDoubleArray(a[i].nVertices);
        env->SetDoubleArrayRegion(padfXARRAY, 0, a[i].nVertices, (jdouble *)a[i].padfX );
        jdoubleArray padfYARRAY = env->NewDoubleArray(a[i].nVertices);
        env->SetDoubleArrayRegion(padfYARRAY, 0, a[i].nVertices, (jdouble *)a[i].padfY );
jdoubleArray panPartStart = env->NewDoubleArray(a[i].nParts);
        env->SetDoubleArrayRegion(panPartStart, 0, a[i].nParts, (jdouble *)a[i].panPartStart );

        int shapeId = a[i].nShapeId;
        int shpType = a[i].nSHPType;
        int nParts = a[i].nParts;
        int dfXMin = a[i].dfXMin;
        int dfXmax = a[i].dfXMax;
        int dfYMax = a[i].dfYMax;
        int dfYMin = a[i].dfYMin;

        recognition_result = env->NewObject(
                        shpObjectClass, shpObjectConstructor, shapeId,shpType,nParts,dfXMin,dfXmax,dfYMin,dfYMax,panPartStart, padfXARRAY, padfYARRAY);
        env->DeleteLocalRef(padfXARRAY);
        env->DeleteLocalRef(padfYARRAY);
        env->SetObjectArrayElement(shapesToReturn,i,recognition_result);
    }

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