CODEWITHSUNDEEP
androidandroid-ndkjava-native-interfacenative
Mohamed Wagdy Khorshid
Mohamed Wagdy Khorshid

Reputation: 557

using jlongArray in JNI with Android NDK

I have those two pieces of code, the first is:

JNIEXPORT jlongArray* JNICALL Java_com_home_overlay_activity_MainActivity_ProcessPointer(JNIEnv* env, jobject) {

    jlongArray blobs_arr;

    return &blobs_arr;
}

and the second is:

JNIEXPORT jlongArray JNICALL Java_com_home_overlay_activity_MainActivity_Process(JNIEnv* env, jobject) {

    jlongArray blobs_arr;

    return blobs_arr;
}

all I want is to return long array to the java code.

The first runs okay while the second not, is there any issue here with returning a long array this way ??

Upvotes: 0

Views: 1396

Answers (2)

Mohamed Wagdy Khorshid
Mohamed Wagdy Khorshid

Reputation: 557

My application was not reading the jni.h but working .. which is weird, after I set the NDKROOT variable it all worked correctly

Upvotes: 0

mbrenon
mbrenon

Reputation: 4941

There are no pointers in Java, so I think that if the first snippet of code actually works, it will not produce what you want at all. It probably returns the memory address of the C jlongArray.

As for the second piece of code, I can't see any problem with it except that it returns an uninitialized object, maybe NULL, maybe some random memory garbage, which probably causes unexpected behavior on the Java side. Maybe you should try initializing it to NULL in the C part, or try making your code snippet more realistic by actually filing the array so you can test the code behavior in real conditions.

Upvotes: 1

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