How to make Volley NetworkImageView worke offline

Question

I use Volley NetworkImageView to download images from internet and show in my listview. Now I want to make Volley NetworkImageView show sa

Answer 1

When you restart your app in offline, the last thing you can rely on just the Disk Cache(i.e. DiskBasedCache). Volley's local cache consist of network data and the response headers. But in this situation, we just need to focusing on the Cache-Control header. For instance, if the server-side return that header is "Cache-Control: max-age=604800", that's tell Volley to cache the response resource for 604800 seconds( source at HttpHeaderParser.parseCacheHeaders() ). Then next time we retrieving the same url's data would checking if exceeded the cache expire time, finally decide retrieve from network or local.

Follow your describe, I suppose your server-side deliver you a value like Cache-Control:must-revalidate|proxy-revalidate|no-cache|no-store, that's why you can't reuse the last retrieved data when you were in offline.

Right now there is question came : once we can manipulate the cache expire time, we'll be capable of increase that time to a large enough value so we can ensure us use that data in offline.

Unfortunately, Volley does not support us to do this. So if you can make the server-side to delivering a viable max-age for this?

If not, I'd suggest you to change to another library which fulfill this desired. and there actually have one can be your friend, is Netroid. It's based on Volley and offered a few improvements, that won't make you change your current code very much. With it, control the expire time would be far easier, and more features would be come with.

mImageLoader = new SelfImageLoader(mRequestQueue, mLruBitmapCache) {
    @Override
    public void makeRequest(ImageRequest request) {
        // you can manipulate the cache expire time with one line code.
        request.setCacheExpireTime(TimeUnit.DAYS, 10);

        // you can even according to the different request to
        // set up the corresponding expire time.
        if (request.getUrl().contains("/for_one_day/")) {
            request.setCacheExpireTime(TimeUnit.DAYS, 1);
        } else {
            request.setCacheExpireTime(TimeUnit.DAYS, 10);
        }
    }
};

the full code was on the project's sample module, i hope this can be helpful.