QMetaObject InvokeMethod method passing integer Array argument - qt

Question

I am fairly new to Qt, and I am trying to do some Android Development. I am working with Qt and using the QAndroidJNIEnvironment. In the code, I am implementing my native method using QMetaObject::invokeMethod to invoke a slot in the QMainWindow header. The problem is that the native method in the java file has a parameter that is a java integer array(equivalent type I believe in QAndroindJniObject is jintArray). I can't find the corresponding c++/Qt type to place in the Q_ARG(type, value ) macro to resolve the argument. Please help me understand what I am doing wrong, as i thought the equivalent type to jintArray was int [], but I receive error when I use that. Thanks in advance for the help.
onReceiveNativeMounted (JNIEnv * env, jobject obj,jint array_index,jintArray version)
{
QMetaObject::invokeMethod(&MainWindow::instance(), "onReceiveMounted"
, Qt::QueuedConnection, Q_ARG(int, array_index),Q_ARG(int[], version));
return array_index;
}
the error i receive is below:
error: no matching function for call to
'QArgument<int []>::QArgument(const char [6], _jarray*&)'
#define Q_ARG(type, data) QArgument<type >(#type, data)
^
As requested, the java function signature is below:
public static native int onReceiveNativeMounted(int array_index, int[] version);

Answer 1

You need to access the java arrays according to the JNI API. The easiest thing to do is to convert the data to a QVector. You need to copy the Java array since its lifetime is not under your control (unless you wish it to be, but that makes life much harder than it needs to be).
QVector toQVector(JNIEnv * env, jintArray arr) {
auto len = (*env)->GetArrayLength(env, arr);
QVector result(len);
auto data = (*env)->GetIntArrayElements(env, arr, 0);
for (int i = 0; i < len; ++i)
result[i] = data[i];
(*env)->ReleaseIntArrayElements(env, arr, data, 0);
return result;
}
It is a bit more performant to perform the call directly from a functor, rather than through invokeMethod. The functor can capture the vector:
int onReceiveNativeMounted (JNIEnv * env, jobject obj, jint array_index, jintArray version)
{
auto window = &MainWindow::instance();
auto vector = toQVector(env, version);
QObject sig;
sig.connect(&sig, &QObject::destroyed, window, [=]{
window->onReceiveMounted(array_index, vector.data());
}, Qt::QueuedConnection);
return array_index;
}