Custom fetcher - Image disappears after scrolling away & returning

[timusus]

Describe the bug

I have a custom fetcher to retrieve images from files via the Storage Access Framework. These images are displayed in the items of a RecyclerView. The image is successfully loaded, but after scrolling the view off-screen, and then back again, the image occasionally disappears, leaving a blank image view. No placeholder, error or fallback drawable is provided.

Interestingly, this does not occur with other custom fetchers that I'm using.

I have bitmapPoolingEnabled(false) and allowHardware(false). I haven't found anything particularly interesting in the logs. If I had to guess, I think some stale Cancelled or Failed event is causing this ViewHolder's ImageView to have its image cleared. Perhaps a race condition related to recycling?

The fetcher looks like so:

class DirectorySongFetcher(private val context: Context) : Fetcher<Song> {

    private val pattern by lazy { Pattern.compile("(folder|cover|album).*\\.(jpg|jpeg|png)", Pattern.CASE_INSENSITIVE) }

    override suspend fun fetch(pool: BitmapPool, data: Song, size: Size, options: Options): FetchResult {
        val parentDocumentFile = if (DocumentsContract.isDocumentUri(context, data.path.toUri())) {
            val parent = data.path.substringBeforeLast("%2F", "")
            if (parent.isNotEmpty()) {
                DocumentFile.fromTreeUri(context, parent.toUri())
            } else {
                null
            }
        } else {
            File(data.path).parentFile?.let { parent ->
                DocumentFile.fromFile(parent)
            }
        }
        
        try {
            parentDocumentFile?.listFiles()
                ?.filter {
                    it.type?.startsWith("image") == true
                            && it.length() > 1024
                            && pattern.matcher(it.name ?: "").matches()
                }
                ?.maxByOrNull { it.length() }
                ?.let { documentFile ->
                    context.contentResolver.openInputStream(documentFile.uri)?.let { inputStream ->
                        return SourceResult(
                            inputStream.source().buffer(),
                            documentFile.type,
                            DataSource.DISK
                        )
                    }
                }
        } catch (e: UnsupportedOperationException) {
            Timber.i("Failed to list files.")
        }

        throw IllegalArgumentException("Failed to find image")
    }

    override fun key(data: Song): String? {
        return "${data.albumArtist}:${data.album}"
    }
}

Expected behavior

When scrolling the RecyclerView back towards an item which is in the memory cache, the item should be displayed, and remain on display without disappearing.

To Reproduce
I don't have a small project to reproduce the issue at this stage, but I can provide access to the private repo on request. You'd need to have some local images stored on disk somewhere.

Logs/Screenshots

A snippet of the logs, taken after having loaded the image successfully, the between scrolling until it was off screen, andd scrolling back again:

2021-01-11 22:45:54.161 1992-1992/com.simplecityapps.shuttle.dev I/RealImageLoader: 🧠 Successful (MEMORY_CACHE) - Album(name='Add Violence', albumArtist='Nine Inch Nails', songCount=10, duration=1635144, year=0, playCount=0, sortKey=Add Violence)
2021-01-11 22:45:54.169 1992-1992/com.simplecityapps.shuttle.dev I/chatty: uid=10317(com.simplecityapps.shuttle.dev) identical 1 line
2021-01-11 22:45:54.170 1992-1992/com.simplecityapps.shuttle.dev I/RealImageLoader: 🧠 Successful (MEMORY_CACHE) - Album(name='Add Violence', albumArtist='Nine Inch Nails', songCount=10, duration=1635144, year=0, playCount=0, sortKey=Add Violence)
2021-01-11 22:45:54.172 1992-1992/com.simplecityapps.shuttle.dev I/RealImageLoader: 🏗  Cancelled - Album(name='10,000 Days', albumArtist='Tool', songCount=22, duration=4551419, year=0, playCount=0, sortKey=10000 Days)
2021-01-11 22:45:54.180 1992-1992/com.simplecityapps.shuttle.dev I/RealImageLoader: 🏗  Cancelled - Album(name='10,000 Days', albumArtist='Tool', songCount=22, duration=4551419, year=0, playCount=0, sortKey=10000 Days)
2021-01-11 22:45:54.310 1992-1992/com.simplecityapps.shuttle.dev I/RealImageLoader: 🚨 Failed - Album(name='Hungry Ghost', albumArtist='Violent Soho', songCount=22, duration=2671177, year=0, playCount=0, sortKey=Hungry Ghost) - java.lang.IllegalArgumentException: Failed to find image
2021-01-11 22:45:54.310 1992-1992/com.simplecityapps.shuttle.dev E/RealImageLoader: java.lang.IllegalArgumentException: Failed to find image
        at au.com.simplecityapps.shuttle.imageloading.coil.fetchers.DirectorySongFetcher.fetch(DirectorySongFetcher.kt:72)
        at au.com.simplecityapps.shuttle.imageloading.coil.fetchers.DirectoryAlbumFetcher.fetch(DirectoryAlbumFetcher.kt:20)
        at au.com.simplecityapps.shuttle.imageloading.coil.fetchers.DirectoryAlbumFetcher.fetch(DirectoryAlbumFetcher.kt:13)
        at coil.intercept.EngineInterceptor$intercept$2.invokeSuspend(EngineInterceptor.kt:403)
        at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
        at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:106)
        at kotlinx.coroutines.scheduling.CoroutineScheduler.runSafely(CoroutineScheduler.kt:571)
        at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.executeTask(CoroutineScheduler.kt:750)
        at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.runWorker(CoroutineScheduler.kt:678)
        at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.run(CoroutineScheduler.kt:665)
2021-01-11 22:45:54.345 1992-1992/com.simplecityapps.shuttle.dev I/RealImageLoader: 🚨 Failed - Album(name='Chocolates & Cigarettes', albumArtist='Angus & Julia Stone', songCount=12, duration=1733504, year=2007, playCount=0, sortKey=Chocolates & Cigarettes) - java.lang.IllegalArgumentException: Failed to find image

'Add Violence' is the name of the Album in question.

Interestingly, there were 3 successfuls memory cache hits in the span of 10ms, starting at 2021-01-11 22:45:54.161.

I've attached a screen recording of the issue:

device-2021-01-11-224947.mp4

Version
Library version: Coil v1.1.0
Device: Pixel 5
OS: Android 11
Compiled against API 30.

[timusus]

I was able to resolve this by wrapping the contents of the fetch() call with withContext(Dispatchers.Default). This was just a stab in the dark, and I'm not sure why this solves the problem..

[colinrtwhite]

Interesting - in the logs you posted java.lang.IllegalArgumentException: Failed to find image comes up a couple times. Is that expected? Also can you confirm when you scroll down up the requests are being served from the memory cache (according to the logs)?

[colinrtwhite]

Going to close this out. It looks like java.lang.IllegalArgumentException: Failed to find image might be related to your missing images. Either way it's not possible to debug the issue without a small sample project that reproduces the bug.

[timusus]

Sorry I didn't get back to you.

The IllegalArgumentException is expected, and logs in the instance where an image cannot be found - this is not related to images which are found and then suddenly dissappear.

If I find the time to write a sample project with the custom fetchers, I'll let you know :)