How can I synchronously retrieve a fallback image from Glide?

[christinabannon]

Glide Version: 4.15.1

Integration libraries:
No

Device/Android Version:
Android Tiramisu

Issue details / Repro steps / Use case background:
What I want to do is be able to log disk cache misses and then on those misses start a task for a URL img request.

Roughly:
Glide check memory then disk:
if in cache: return img synchronously (or very quickly if on disk cache)
else: return fallback image synchronously (or very quickly if on disk cache)
log cache miss
start task to load img from resource into cache

The code is something like this:

public static ListenableFuture<Bitmap> getBitmapFromCache(
      GlideFuturesWrapper glideFuturesWrapper, RequestManager requestManager, String url) {

    return glideFuturesWrapper.submit(
        requestManager
            .asBitmap()
            .apply(new RequestOptions().onlyRetrieveFromCache(true))
            .load(url));
  }

 public static Icon getIcon(Context context) {
    Icon icon;
    GlideFuturesWrapper glideFuturesWrapper = new GlideFuturesWrapper();
    RequestManager requestManager = Glide.with(context);

    ListenableFuture<Bitmap> futureBitmap =
        getBitmapFromCache(glideFuturesWrapper, requestManager, url);
    try {
      Bitmap bitmap = futureBitmap.get();
      icon = bitmapToIcon(bitmap);
    } catch (Exception e) {
      Log miss
      icon = getFallbackIcon();
      loadBitmapFromFifeUri(glideFuturesWrapper, requestManager, url);
    }
    return icon;
  }

The issue I am running into is that future.get() throws an exception every time there is a cache miss. I am aware that this is the intended functionality.

It would take a major refactoring effort to change the Icons passed around in this program to ImageViews, so I want for Glide to return a Bitmap as opposed to loading into an ImageView. It seems pointless to load into an ImageView that I immediately pull a Bitmap out of, and my fear is that I would get the fallback in a case where the img is on disk cache.

I currently have it in a try... catch block to deal with getting a fallback. This makes me question if there is some Glide method I may have overlooked. Does Glide have a way to synchronously serve a fallback image on an error?

Stack trace / LogCat:

GlideException: Failed to load Resource

[sjudd]

There is no simple way to do this in Glide. ListenableFuture can provide exactly one result, so there's no reasonable API I can think of where Glide could return a fallback from the Future (indicating that the future is complete), but still continue to load the url in the background.

As an aside - Future#get() calls are not very efficient because they block multiple threads. .onlyRetrieveFromCache() does not make the request fast because it will still decode resources from the disk cache which can take a non-trivial amount of time. I can't quite tell what the use case is here. If you're not loading into an ImageView, you could make the method return a ListenableFuture using a transformation on the ListenableFuture instead of making the method blocking. That's also not a trivial refactor.

Does this answer your question?

[christinabannon]

Yes it does, thank you I appreciate your response.

One more (perhaps very silly) clarification if you have the time. .skipMemoryCache(true) would have a query for an image not search the memory cache for the image, but would it still save the image to the memory cache once it is retrieved from wherever?