Tree View Menu with RecyclerView
I had long wanted to write a tree view demo. Previously, I used TreeViewList (a ListView wrapper) or ExpandableListView for multi-level menus. Eventually I realized there is no need for custom views – just use RecyclerView and manage the data flattening yourself. The core idea: recursively flatten a nested data structure into a linear list, then use notifyItemRangeInserted / notifyItemRangeRemoved to handle expand and collapse. ...