Invalidate cache in Picasso

Question

I load an image from disk using Picasso, e.g., Picasso.with(ctx).load(new File("/path/to/image")).into(imageView), but whenever I save a new image in that file, and refresh my ImageView, Picasso still has the bitmap cached.

Is it possible to invalidate the cache in Picasso?

Answer 1

Another option is to save the new image into a different file than the original. Since the Picasso bitmap cache is keyed off of the file path, loading the new image from a different file will result in a cache miss. This also has the side benefit of not having to clear the entire cache.

Answer 2

You can skip memory cache by skipMemoryCache()

see the following

        Picasso.with(this)
            .load(IMAGE_URL)
            .skipMemoryCache()
            .placeholder(R.drawable.placeholder)
            .error(R.drawable.no_image)
            .into(mImageViewPicasso);

gradle compile "com.squareup.picasso:picasso:2.4.0"

Answer 3

Abort memory cache and disk cache check by indicate memory policy by flag: emoryPolicy.NO_CACHE and NetworkPolicy.NO_CACHE as below code snippet:

   mPicasso.with(mContext)
            .load(url)
            .memoryPolicy(MemoryPolicy.NO_CACHE )
            .networkPolicy(NetworkPolicy.NO_CACHE)
            .resize(512, 512)
            .error(R.drawable.login)
            .noFade()
            .into(imageView);

Answer 4

The order of search image in Picasso is: Memory cache -> Disk cache -> Network

So there are few scenario we need to invalidate cache in Picasso:

1.Invalidate memory cache:

• Usercase: When image already update in disk cache or remote host

• Solution: Clear cache of Url, File, Uri if exist

  mPicasso.with(appContext).invalidate(File);
  mPicasso.with(appContext).invalidate(Url);
  mPicasso.with(appContext).invalidate(Uri);
  

.

2.Invalidate memory cache and disk cache Online

※note: Online mean update directly to ImageView

• User case: Image updated on remote host

• Solution: Abort image on memory cache and disk cache then request image on remote host

  mPicasso.with(appContext)
      .load(url)
      .memoryPolicy(MemoryPolicy.NO_CACHE )
      .networkPolicy(NetworkPolicy.NO_CACHE)
      .into(imageView);
  

  -> Abort memory cache and disk cache

.

3.Invalidate memory cache and disk cache Offline

※ note: Offline mean update not update to ImageView, just background fetch to using later

• User case: You know image on remote host updated, but only want to update cache only to using afterward (not update into image view)

• Solution: fetch only

   mPicasso.with(appContext)
      .load(url)
      .memoryPolicy(MemoryPolicy.NO_CACHE)
      .networkPolicy(NetworkPolicy.NO_CACHE)
      .fetch();
  

※Note: Using fetch() is good but it also consume network resource, so please consider carefully, check scenario 4 in below for better solution

4.Invalidate memory cache and disk cache Offline if disk cache is exist

• User case: Only invalidate cache if already exist in disk cache

• Solution: Should check disk by using parameter: NetworkPolicy.OFFLINE cache before fetch

   mPicasso.with(appContext)
      .load(url)
      .memoryPolicy(MemoryPolicy.NO_CACHE)
      .networkPolicy(NetworkPolicy.OFFLINE)
      .fetch(new Callback() {
          @Override
          public void onSuccess() {
              //Success: mean disk cache exist -> should do actual fetch
              picasso.load(url).fetch();
          }
  
          @Override
          public void onError() {
          //Failed: mean disk cache not exist
      }
  });
  

Picasso is an amazing libs, I hope squareup will add more convenience API to manage cache in upcoming future.

Answer 5

use shutdown() instead As per source code; shutdown will stop accepting further request as well as clear all cache

 /** Stops this instance from accepting further requests. */
  public void shutdown() {
    if (this == singleton) {
      throw new UnsupportedOperationException("Default singleton instance cannot be shutdown.");
    }
    if (shutdown) {
      return;
    }
    cache.clear();
    cleanupThread.shutdown();
    stats.shutdown();
    dispatcher.shutdown();
    for (DeferredRequestCreator deferredRequestCreator : targetToDeferredRequestCreator.values()) {
      deferredRequestCreator.cancel();
    }
    targetToDeferredRequestCreator.clear();
    shutdown = true;
  }

Also you can not shutdown singleton instance. So you need to have instance variable for Picasso. Do not forget to reinitialize picasso instance everytime you shutdown() it in order to reuse it

Answer 6

What you can do if you want to delete all cache at once, is to create a custom Picasso.LruCache, and then use the clear method on it.

Here is a sample:

Picasso.Builder builder = new Picasso.Builder(this);
LruCache picassoCache = new LruCache(this);
builder.memoryCache(picassoCache);
Picasso.setSingletonInstance(builder.build());

To clear the cache:

picassoCache.clear();