making some objects parcelable, it's better to send the set up us a bundle instead of creating different params for the intent
solving bug fix that was causing an incorrect behaviour when zooming in/out in pictures retrieved from an url (because the PhotoViewAttacher was attached previously to retrieving the picture with Picasso and there was a conflict with the imageView dimen.).

removing final from private methods (don't know I was thinking about when I wrote it, things of programming at late hours...), making PhotoLoader abstract (we do not want it to be instantiated directly).