Provide better expand/collapse animations

[WonderCsabo]

Currently the library just calls up to notifyItemRemoved() when collapsing an item and notifyItemInserted() when expanding an item. With the DefaultItemAnimator (which is RecyclerView uses by default, hence most of the projects including your examples do), this will result in simply fade in/out animations when expanding the items and collapsing the items.

However, this does not really feel a "real" expansion operation. The expansion would be better represented by a shift animation. It would be nice if the lib would provide an ItemAnimator which would animate the expand/collapse action in this manner.

[dgreenhalgh]

I agree - this is something we've discussed for a future release. If you end up making this improvement in your project, please feel free to contribute it