when would Exception in the RequestListener.onException(Exception e, Object model, Target<Drawable> target, boolean isFirstResource) be null?

[GothicFox]

hi guys, i used glide 3.8.0 snap-shot，and my app got on line, recently some users told that after used the app for a while, the images in the app didn't show. so i get some logs from these users. i found that there are lots of fails , and the RequestListener.onException was called, but what makes me confused is that the param Exception e in the method RequestListener.onException is null...but i didn't write in my own code that pass a null exception in the RequestListener.onException, so what would cause glide return a null exception or on what circumstances would a null exception would be passed? why failed without information?

i really need a nonnull exception to solve the problem.and i really don't know how to fix this, any help would be appreciate! Thanks!

[TWiStErRob]

Don't remember all the cases without research, but the most common one is an invalid image (e.g. server returns html instead of image bytes). Glide uses BitmapFactory behind the scenes, and that, instead of throwing an exception, returns null and logs the failure reason. This null is then passed up the chain and becomes a no-exception (failure without exception). Fixing this in 3.x would be a breaking change for many apps, I think v4 is fixed in this regard, @sjudd?

[GothicFox]

@TWiStErRob
em ...i may recently find out what cause this, although i'm not sure right now.
first i got a android phone with almost full external disk, with about less then 5MB disk space, and then i installed my app, and after that or after a while using my app, the images didn't show with an null exception.

As you can see that i set glide with external disk cache, about 200MB when init glide, and i always use DiskCacheStrategy.SOURCE as the disk cache strategy for every image loading.

I just want to know would a insufficient external disk cache cause glide not showing the images? if that is true, how can i prevent it from happening?

by the way, i use Target.SIZE_ORIGINAL for almost every request, because i will control my image size by url like: http://xxxx_360x360_q90.jpg, which will get me 360x360 image~

thanks a lot!

[GothicFox]

@TWiStErRob
after a few time of debug, i found something in DecodeJob:

private Resource<T> decodeSource() throws Exception {
        Resource decoded = null;

        Object var5;
        try {
            long startTime = LogTime.getLogTime();
            Object data = this.fetcher.loadData(this.priority);
            if(Log.isLoggable("fishLoader_DecodeJob", 2)) {
                this.logWithTimeAndKey("Fetched data", startTime);
            }

            if(!this.isCancelled) {
                decoded = this.decodeFromSourceData(data);
                return decoded;
            }

            var5 = null;
        } finally {
            this.fetcher.cleanup();
        }

        return (Resource)var5;
    }

after Object data = this.fetcher.loadData(this.priority); the data is ok, and then it goes to decoded = this.decodeFromSourceData(data); However, in this.decodeFromSourceData:

private Resource<T> decodeFromSourceData(A data) throws IOException {
        Resource decoded;
        if(this.diskCacheStrategy.cacheSource()) {
            decoded = this.cacheAndDecodeSourceData(data);
        } else {
            long startTime = LogTime.getLogTime();
            decoded = this.loadProvider.getSourceDecoder().decode(data, this.width, this.height);
            if(Log.isLoggable("fishLoader_DecodeJob", 2)) {
                this.logWithTimeAndKey("Decoded from source", startTime);
            }
        }

        return decoded;
    }

    private Resource<T> cacheAndDecodeSourceData(A data) throws IOException {
        long startTime = LogTime.getLogTime();
        DecodeJob.SourceWriter writer = new DecodeJob.SourceWriter(this.loadProvider.getSourceEncoder(), data);
        this.diskCacheProvider.getDiskCache().put(this.resultKey.getOriginalKey(), writer);
        if(Log.isLoggable("fishLoader_DecodeJob", 2)) {
            this.logWithTimeAndKey("Wrote source to cache", startTime);
        }

        startTime = LogTime.getLogTime();
        Resource result = this.loadFromCache(this.resultKey.getOriginalKey());
        if(Log.isLoggable("fishLoader_DecodeJob", 2) && result != null) {
            this.logWithTimeAndKey("Decoded source from cache", startTime);
        }

        return result;
    }

try to put and get from cache... in this.diskCacheProvider.getDiskCache().put(this.resultKey.getOriginalKey(), writer);

//DiskLruCacheWrapper

    public void put(Key key, Writer writer) {
        String safeKey = this.safeKeyGenerator.getSafeKey(key);
        this.writeLocker.acquire(key);

        try {
            Editor e = this.getDiskCache().edit(safeKey);
            if(e != null) {
                try {
                    File file = e.getFile(0);
                    if(writer.write(file)) {
                        e.commit();
                    }
                } finally {
                    e.abortUnlessCommitted();
                }
            }
        } catch (IOException var15) {
            if(LogSwitch.isLoggable("fishLoader_DiskLruCacheWrapper", 5)) {
                Log.w("fishLoader_DiskLruCacheWrapper", "Unable to put to disk cache", var15);
            }
        } finally {
            this.writeLocker.release(key);
        }

    }

the Editor in Editor e = this.getDiskCache().edit(safeKey); is some how always null...so i think that the put action is not success? and then trying to get Resource from Cache: Resource result = this.loadFromCache(this.resultKey.getOriginalKey());

private Resource<T> loadFromCache(Key key) throws IOException {
        File cacheFile = this.diskCacheProvider.getDiskCache().get(key);
        if(cacheFile == null) {
            return null;
        } else {
            Resource result = null;

            try {
                result = this.loadProvider.getCacheDecoder().decode(cacheFile, this.width, this.height);
            } finally {
                if(result == null) {
                    this.diskCacheProvider.getDiskCache().delete(key);
                }

            }

            return result;
        }
    }

the cacheFile is null here...so we get a null exception in EngineRunnable.onLoadFailed...and failed?

i didn't much understand the logic in the code, but i guess that if the disk space is not enough, the the "put to disk" action should fail, and then "get from the cache" fail also? at this moment, shouldn't we get resource by directly decoding and skip the disk cache?

as i say, i don't fully understand the logic here, just want to solve the problem ,any help would be appreciated, thanks!