Passing Byte Array From Native Code To The Java Side

My goal is passing a byte array of variable length from native code to Java side. The Java class instance method takes bytearray as its argument: private void writeBuffer(final byt

Solution 1:

Try calling ReleasePrimitiveArrayCritical before you call CallVoidMethod.

Solution 2:

Below example works for passing char[] from C code to Java byte[].

void JNICALL Java_com_example_testapplication_MainActivity_getJNIByteArrayArg(JNIEnv    *jenv, jobject jobj)
{
jclass clazz = (*jenv)->FindClass(jenv, "com/example/testapplication/MainActivity"); // class path
jmethodID mid = (*jenv)->GetMethodID(jenv, clazz, "addData", "([B)V");// function name

jbyteArray retArray;
char data[] = {'a','b',3,4,5};
int data_size = 5;
if(!retArray)
retArray = (*jenv)->NewByteArray(jenv, data_size);

if((*jenv)->GetArrayLength(jenv, retArray) != data_size)
{
    (*jenv)->DeleteLocalRef(jenv, retArray);
    retArray = (*jenv)->NewByteArray(jenv, data_size);
}

void *temp = (*jenv)->GetPrimitiveArrayCritical(jenv, (jarray)retArray, 0);
memcpy(temp, data, data_size);
(*jenv)->ReleasePrimitiveArrayCritical(jenv, retArray, temp, 0);

(*jenv)->CallVoidMethod(jenv, jobj, mid, retArray);
}
publicvoid addData(byte[] data) {
System.out.println("Buyya: From C: " + newString(data));
}

Solution 3:

You can also use SetByteArrayRegion for setting jbyteArray content:

(*env)->SetByteArrayRegion(env, retArray, 0, data_size, decoded_frame->data[0]);