getting NegativeByteArraySizeException from ContentResolver's openAssetFileDescriptor method for reading vCardUri. Is there any workaround to fix it?

Question

I am creating a .VCF file for backing up the Contacts. The process of creating and inserting the data get failed because of the FileDescriptor's method getDeclaredLength which returns the size -1 for the length of the vCard-URI which I got from the ContentResolver's openAssetFileDiscritor method.

This is the exact same Question as asked here by Balakrishna Avulapati. but the only problem for asking the same question here is that, the proposed solution is a bit hard for me to understand. which do not salve my problem. The comment by @pskink in the solution of above link could be useful but i am anable to find the full source code, as there is only 1 line provided in the comment.

I am using the fllowing code,

Uri uri = Uri.withAppendedPath(ContactsContract.Contacts.CONTENT_VCARD_URI, lookupKey);
AssetFileDescriptor fd = resolver.openAssetFileDescriptor(uri, "r");
FileInputStream fis = fd.createInputStream();
byte[] b = new byte[(int)fd.getDeclaredLength()];
fis.read(b);

Please give your kind sugestions. Thank you :)

Answer 1

So I figured it out by myself, and I'm posting the answer in case of somebody get the similar problem and stuck for the solution. So the code before byte[] b = new byte[(int)fd.getDeclaredLength()]; is same. Change this line to byte[] buf = readBytes(fis); and the method readBytes(FileInputStream fis) is below.

public byte[] readBytes(InputStream inputStream) throws IOException {
    // this dynamically extends to take the bytes you read
    ByteArrayOutputStream byteBuffer = new ByteArrayOutputStream();

    // this is storage overwritten on each iteration with bytes
    int bufferSize = 1024;
    byte[] buffer = new byte[bufferSize];

    // we need to know how may bytes were read to write them to the byteBuffer
    int len = 0;
    while ((len = inputStream.read(buffer)) != -1) {
        byteBuffer.write(buffer, 0, len);
    }

    // and then we can return your byte array.
    return byteBuffer.toByteArray();
}

Hope this help. Cheers