How can I get short[] from a ByteBuffer

Question

I am using JNI code in an Android project in which the JNI native function requires a short[] argument. However, the original data is stored as a ByteBuffer. I'm trying the convert the data format as follows.

ByteBuffer rgbBuf = ByteBuffer.allocate(size);
...    
short[] shortArray = (short[]) rgbBuf.asShortBuffer().array().clone();

But I encounter the following problem when running the second line of code shown above:

E/AndroidRuntime(23923): Caused by: java.lang.UnsupportedOperationException
E/AndroidRuntime(23923): at Java.nio.ShortToByteBufferAdapter.protectedArray(ShortToByteBufferAdapter.java:169)

Could anyone suggest a means to implement the conversion?

Cat · Answer 1 · 2012-08-13T08:29:56.503

7

The method do this is a bit odd, actually. You can do it as below; ordering it is important to convert it to a short array.

short[] shortArray = new short[size/2];
rgbBuf.order(ByteOrder.LITTLE_ENDIAN).asShortBuffer().get(shortArray);

Additionally, you may have to use allocateDirect instead of allocate.

edited Aug 13 '12 at 08:29

answered Aug 13 '12 at 08:16

Cat

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Could you explain a bit more why using allocateDirect()? Since I don't find any hints from the android documentation. – bei Aug 13 '12 at 08:54
It's a hunch based on [a bug report](http://code.google.com/p/android/issues/detail?id=24327) that was filed. It may be unrelated, but I figured it was worth mentioning. – Cat Aug 13 '12 at 18:06

score 1 · Answer 2 · edited May 23 '17 at 11:45

I had the same error with anything that used asShortBuffer(). Here's a way around it (adapted from 2 bytes to short java):

short[] shortArray = new short[rgbBuf.capacity() / 2]);
for (int i=0; i<shortArray.length; i++)
{   
    ByteBuffer bb = ByteBuffer.allocate(2);
    bb.order(ByteOrder.LITTLE_ENDIAN);
    bb.put(rgbBuf[2*i]);
    bb.put(rgbBuf[2*i + 1]);
    shortArray[i] = bb.getShort(0);
}

How can I get short[] from a ByteBuffer

2 Answers2

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