Android: SortedList with duplicates

Question

I have some problems understanding RecyclerViews SortedList.

Lets say I have a very simple class only having a very simple class holding data:<

Answer 1

SortedList does not keep any mapping by ids (because there are no ids in the API). So when the sorting criteria changes (a to b in your case), SortedList cannot find the existing element.

You can keep the id mapping yourself, then have your add method as follows:

void add(Item t) {
  Item existing = idMap.get(t.id);
  if (existing == null) {        
     sortedList.add(t);
  } else {
     sortedList.updateItemAt(sortedList.indexOf(existing), t);
  }
  idMap.put(t.id, t);
}

You'll also need to implement a remove method to remove the item from the idMap.