Recyclerview with expandable items

Example implementation on how to create expandable items in a RecyclerView.

Features

#1 Expand/collapse items with a slide animation

#2 Only one item can be expanded at a time

#3 Item moves as it is expanded

#4 Day/Night support

Implementation details

#1 Architecture

MVVM was used. The ViewModel fetches data from a Repository, transforms it and then exposes to the View for it to observe through a LiveData.

#2 View

A compound view was made to contain the layout used in each item in the RecyclerView. This makes easier to get the necessary parts of the view to animate.

#3 Animation

Was used ValueAnimator to in each frame change the height of the item to give the impression of expanding/collapsing.

In the expand animation the RecyclerView is moved along the animated item so if gets off screen, it gets back to it again.

Delay was used in the expand animation so it would start only after the animation of any other item closing.

#4 Adapter

DiffUtil and Payloads were used to indicate to a ViewHolder than an item must be animated.