How to use OkHttp 2.0 API to download stuff on behalf of Picasso.

OkHttpDownloader.java

public class OkHttpDownloader implements Downloader
{
    @Override
    public Response load(Uri uri, boolean b) throws IOException
    {
      HttpClientProxy clientProxy = // create a HttpClient proxy that
                                    // forwards stuff to a real OkHttpClient
                                    // or some mocked class
      Request request = new Request.Builder()
                    .url(uri.toString())
                    .build();
      com.squareup.okhttp.Response response = clientProxy.newCall(request).execute();
      if (!response.isSuccessful())
      {
        throw new ResponseException(response.code() + " " + response.message());
      }
      // we could be stricter here, but this should be enough to separate non-image responses
      if (!response.body().contentType().type().equals("image"))
      {
        throw new ResponseException("unsupported Content-Type returned: " + response.body().contentType());
      }
      return new Response(response.body().byteStream(), false, response.body().contentLength());
    }
}

OkHttpPicassoProvider.java

public class OkHttpPicassoProvider implements Provider<Picasso>
{
    @Inject
    protected Application mApplication;

    private Picasso mInstance;

    @Override
    public synchronized Picasso get()
    {
        if (mInstance == null)
        {
            mInstance = create();
        }
        return mInstance;
    }

    private Picasso create()
    {
        return new Picasso.Builder(mApplication)
                .downloader(new OkHttpDownloader())
                .loggingEnabled(BuildConfig.DEBUG)
                .listener(new Picasso.Listener()
                {
                    @Override
                    public void onImageLoadFailed(Picasso picasso, Uri uri, Exception exception)
                    {
                        Log.e("failed to load image from URI " + uri);
                    }
                })
                .build();
    }
}