Calling from C++ Java method which returns List<int[]>

[Ruslan Baratov]

Hi,

I'm trying to call getSupportedPreviewFpsRange Java method from C++. This method has signature List<int[]> getSupportedPreviewFpsRange () so first I do:

QJNIObjectPrivate rangeListNative = m_parameters.callObjectMethod("getSupportedPreviewFpsRange", "()Ljava/util/List;");

which returns valid object. Then I try to call get method to access jintArray (?).

Got undefined reference error:

rangeListNative.callMethod<jintArray>("get", "(I)[I", i);

Method not found error:

rangeListNative.callObjectMethod<jintArray>("get", "(I)[I", i);

Returns null pointer:

rangeListNative.callObjectMethod("get", "(I)[I", i);

What is the right way to do it?

[Carmoneer]

I have a similar method signature that I use for Android. I have no idea if this will be beneficial for you or not...
Possibly replace "(I)Ljava/lang/Object" with "(I)Ljava/lang/List"

QAndroidJniObject jResult =resultsVector.callObjectMethod("get", "(I)Ljava/lang/Object;", i);

[Ruslan Baratov]

@Carmoneer but how can I get value for jintArray from it? is it a correct way:

QJNIObjectPrivate jRange =resultsVector.callObjectMethod("get", "(I)Ljava/lang/Object;", i);
jintArray jRange = static_cast<jintArray>(range.object());

?

[Ruslan Baratov]

Actually it works :) Here is a full code snippet:

QJNIObjectPrivate rangeListNative = m_parameters.callObjectMethod("getSupportedPreviewFpsRange", "()Ljava/util/List;");
int count = rangeListNative.callMethod<jint>("size");
for (int i = 0; i < count; ++i) {
    QJNIObjectPrivate range = rangeListNative.callObjectMethod("get", "(I)Ljava/lang/Object;", i);

    jintArray jRange = static_cast<jintArray>(range.object());
    jint* rangeArray = env->GetIntArrayElements(jRange, 0);

    AndroidCamera::FpsRange fpsRange;

    /* int */ fpsRange.min = rangeArray[0];
    /* int */ fpsRange.max = rangeArray[1];

    env->ReleaseIntArrayElements(jRange, rangeArray, 0);

    rangeList << fpsRange;
}

wonder if it's correct (?).

[Carmoneer]

Oh, great! Glad to hear it is working. :) Everything looks good to me, however, I am certainly no expert.

[benlau]

@Ruslan-Baratov said:

wonder if it's correct (?).

I just use the "get" method. Not sure is your method "correct", but it looks fine.

My code:
https://github.com/benlau/quickandroid/blob/master/qasystemdispatcher.cpp#L41

[Ruslan Baratov]

I just use the "get" method

@benlau I use "get" method too but only for Java object. As far as I understand element of the list is not a Java object, it's integer array int[].

[benlau]

@Ruslan-Baratov said:

I just use the "get" method

@benlau I use "get" method too but only for Java object. As far as I understand element of the list is not a Java object, it's integer array int[].

Everything in Java is an object. Regardless of the actual storage method , List<T> is in fact an array of java.lang.Object, but you could use it like an int[] .

[Ruslan Baratov]

Everything in Java is an object

@benlau Okay, thanks for the information. Good to know :)