ExpandableLayout use ConstraintSet for animate the state changing.
Bindroid is an open-source utility library for Android apps whose primary goal is to simplify binding UI to data. It introduces an observability pattern for model objects and a number of simple methods for quickly binding these objects to your user interfaces. The result is a responsive, always-consistent and up-to-date user experience without having to write all of the glue to ensure that your UI is updated whenever the data it presents changes.