Allow fallback to take a full request rather than just drawables

[sjudd]

No description provided.

[TWiStErRob]

It's vastly more complicated to do so, and in many ways similar to functionality you can already get out of thumbnail.

I agree it's complex, here are some thoughts:

It's similar to thumbnail, but there's a big difference: thumbnail races for onResourceReady while fallback should only be started if model is null, that is taking the main load's place and giving null a whole new meaning. Thumbnail is also temporal (while the full load finishes), while again fallback is terminal, once it's displayed it shouldn't be overwritten with anything.

I think Andre's use case is a really good example (little bit enhanced here):

load(programme.url)
.thumbnail(0.2)
.fitCenter()
.fallback(
    load(programme.series.url)
    .thumbnail(0.4)
    .transformation(...)
    .fallback(
        load(programme.channel.url)
        .sizeMultiplier(0.5)
        .centerCrop()
    )
)

with the only exception that he expects HTTP 404 so fallbacks should be errors?!

[vsahu1986]

+1

[vipinhelloindia]

+1

[quentin23soleil]

+1

[AndreasBackx]

+1

[dadouf]

+1

[JesperSjoquist]

+1

[Ribesg]

+1 I'm showing pictures against a Stream description. I would like to show 1) a thumbnail if available 2) A game image if not 3) a default image if none is available

[sebnapi]

+1 Use-Case: Fallback to different Images. Imagine a music-player that could download covers from last.fm or xyz.com or from the file or in the end generate a cover.

[pkuprys]

+1

We have a lot of images we are loading in recycler views. An image can have more than one type, but depending on the resource/environment, not all types are available. So we first try to load type A, if it fails, we try to load type B, if that fails we try type C, so on and so forth.

We currently do this by calling load() in a listener's onException() method with the next URI and return true. If we run out of URIs to try, we return false. Ideally, we would like to pass in a list of URIs to the load() method, and just have our listener deal with the final success/failure scenario after either one of the URIs succeeds, or all have failed.

[agbison]

+1

[TWiStErRob]

@"+1"s (everyone): can you please edit your comments to include your use case, it may help the implementor to choose the right way of implementing serving all of these use cases.

[bspurgin]

+1 - same use case as @pkuprys

[eanderso]

+1 I have a URL which may contain a specific image (if the vendor has a custom image) - however if it doesn't exist I need to hit another URL to get 'default' version of this

[mobiRic]

+1 - much the same use case as @pkuprys

On the server we resize our images into different resolutions for devices to fetch based on screen size. Not all images. However the resizing is not guaranteed for all images, so we would like to fallback to the original image in that case.

[TWiStErRob]

@pkuprys @bspurgin @mobiRic @eanderso I see how convenient that would be.
See #606 for an example of how it could be done simply with current API in the meantime.

[TWiStErRob]

@sjudd I'm not entirely sure if this is fixed. Didn't run it, but just looking at the code I can't see how I could do this:

• load a URL
• if that URL is null, show an image from some other source (see programme/series/channel example above)
• if any/all of those URLs fail to load, show an error image via a Glide load (not drawable)

[sjudd]

I've added an error() method that will let you start an arbitrary new load when a request fails. A request will fail if the model is null or if the load fails for some other reason during the decode process.

I believe the above covers your first and third point. Your second point is covered either by the existing fallback drawable, or by a simpleif (model == null) nullRequest.into(...) else normalRequest.into(...). The additional complexity in the library of trying to treat a normal error and a null model error separately is substantial and almost certainly not worth the effort given how easy it is to just write an if/else statement.

Does that make sense?

[TWiStErRob]

Ok, thanks, makes sense. Just wanted to clarify it was intentional.