Write an expandable list view

I need a simple one Fragement application with an expandable RecyclerView. Which would show the list of items. Items are located in sql table (id, name, parentId) Each item can refer to another item. Root items have parentId = 0. Initially list should be collapsed. User can expand a node by pressing to icon at left of item. Press on item shows a message box with id, name and parentId. No design is required.