Picasso never caches to disk on emulator

Question

I'm using picasso to load images for my app. None are particularly large, but its only ever caching to memory so I'm running into out of memory errors on image heavy pages. Is there something I need to set manually in either picasso or the emulator to enable disk caching?

Answer 1

Have you provided a custom Downloader into Picasso? There are a few things you should make sure of:

1. Do you have permission to write to the specified cache folder?
2. Is your cache size restriction large enough for the images Picasso is downloading?

Here is an example implementation for writing the images to the cache directory on the SD card:

// Obtain the external cache directory
File cacheDir = context.getExternalCacheDir();
if (cacheDir == null) {
    // Fall back to using the internal cache directory
    cacheDir = context().getCacheDir();
}
// Create a response cache using the cache directory and size restriction
HttpResponseCache responseCache = new HttpResponseCache(
        cacheDir,
        10 * 1024 * 1024);
// Prepare OkHttp
httpClient = new OkHttpClient();
httpClient.setResponseCache(responseCache);
// Build Picasso with this custom Downloader
new Picasso.Builder(getContext())
         .downloader(new OkHttpDownloader(httpClient))
         .build();

I haven't tested this, but there also exists the possibility that the server is returning an HTTP header instructing OkHttp to never cache. For testing, I'd suggest:

1. Enable Picasso's setDebugging(true); you should see a yellow marker when the image is reloaded from disk.
2. Kill your application when testing the cache; a green marker indicates it's coming from the memory cache.
3. Download an image from a static location where you're certain the server isn't sending cache-expiry/no-pragma headers.

Answer 2

From:

How to implement my own disk cache with picasso library - Android?

//this code from https://developer.android.com/reference/android/net/http/HttpResponseCache.html
try {
       File httpCacheDir = new File(context.getCacheDir(), "http");
       long httpCacheSize = 10 * 1024 * 1024; // 10 MiB
       HttpResponseCache.install(httpCacheDir, httpCacheSize);
}catch (IOException e) {
       Log.i(TAG, "HTTP response cache installation failed:" + e);
}

And enable debugging to check the cache is working Picasso.with(getContext()).setDebugging(true);