Content resolver returns wrong size

Question

I am picking an image from the gallery and querying its size via ContentResolver API, it returns 29kb.

However when I check the file via adb using ls -al it is 44kb

here is how I query the size of the image:

    private fun getFileInfo(contentResolver: ContentResolver, fileUri: Uri): Pair<String, Long>? {
    val projection = arrayOf(MediaStore.MediaColumns.DISPLAY_NAME, MediaStore.MediaColumns.SIZE)
    val metaCursor = contentResolver.query(fileUri, projection, null, null, null)
        metaCursor?.use {
            if (it.moveToFirst()) {
                val displayNameIndex = it.getColumnIndex(MediaStore.MediaColumns.DISPLAY_NAME)
                val sizeIndex = it.getColumnIndex(MediaStore.MediaColumns.SIZE)
                return Pair(it.getString(displayNameIndex), it.getLong(sizeIndex))
            }
    }
    return null
}

I am using an Oreo Emulator. I have also checked via emulator's tools, file browser shows as 29kb on the other hand file details shows 45kb. What is going on?

Here are the images from file browser:

Another side note, above situation can be reproducible every time when using camera app on emulator with Android 26-Oreo emulator, however it is fine with emulator Android 25-Nougat.

I have checked, new Document API also returns 29kb

Lifton

Did you tried to force media store to rescan? Maybe size was changed and it is not updated in the database – Ancel

@Ancel It is a Google API emulator, so cannot run root commands, but restarted the emulator. – Lifton

root commands? I'm pretty sure that Intent.ACTION_MEDIA_SCANNER_SCAN_FILE doesn't need root – Ancel

@Ancel I have tried after your comment, not helping. – Lifton

Is it not because one is the real size of the file, and the other one the space occupied by the file on the storage? – Coleen

@Coleen is it so different as 29kb vs 45kb? Secondly why and how it is changed on Oreo? I am asking from content provider to give me a stream and a size. Where is the logic on that if size does not match with stream length... – Lifton

Answer 1

I had a similar issue. The ContentResolver was underestimating the true filesize by about 400 bytes. I solved it using a similar approach to that explained in How to correctly get the file size of an android.net.Uri? :

ParcelFileDescriptor pfd = getContentResolver().openFileDescriptor(imageUri, "r");
fileLength = pfd.getStatSize();
pfd.close();

Koestler

I wouldn't recommend using it inside a loop. When I used this function in a loop with 10000 objects, it caused a delay of about 10-20 seconds. – Artiste

Answer 2

Android 8.0 (Oreo) introduced the 'SDCardFS' filesystem, which replaced 'FUSE' on the /sdcard partition.

it is possible that this new filesystem has a large cluster size and is therefore not able to allocate exactly 29kb, but instead the smallest block larger than 29kb, which in your case is 44.*kb.

The difference between ls -al and file details is probably caused by different rounding.

Namhoi

I doubt if that is the case. I have took several shots; when an image showed 35kb, details showed 53kb on the same emulator. And side note, 8.1 Emulator also returns different values, however difference is much more small. – Lifton

@guness, does this only happen on images? have you tried different image formats? EDIT: sometimes the filesystem doesn't deallocate space after the file has shrunk, causing fragmentation, this also might be the case if you've edited the file a bunch. – Namhoi

Videos seems to be fine, and I haven't edited images ever. Lastly Camera takes images in one format only: jpg Edit: I believe this is related to following question: #21882822 – Lifton