RecyclerView.Adapter notifyItemChanged（）与异步网络更新？

Question

I have a RecyclerView using a LinearLayoutManager, and a custom RecyclerView.Adapter. When a user long-clicks an item, it triggers an asynchronous network refresh of only that item. I know the item's position at the time of the long-click, and I can pass that position on to the network refreshing function. However by the time the refresh is complete and notifyItemChanged() is called, the user may have added a new item or removed one. So while the refreshed item may have originated from position 4, by the time the refresh is done it could be in 3 or 5 or somewhere else.

How can I ensure that I call notifyItemChanged() with the right position parameter?

Answer 1

Here are three possible solutions:

1. Call notifyDataSetChanged() instead and call it a day.

2. Keep a separate map of items by a unique ID in your adapter. Have the network refresh return item along with the unique ID. Access the item through the ID map and figure out its position. Obviously if there is no unique ID for your items, this isn't an option.

3. Keep track of the item(s) being refreshed. Register your own AdapterDataObserver and track all the inserts and updates, calculating the new position of the item each time and saving it until refresh returns.

Answer 2

While notifyDataSetChanged() will do the trick, if it is essential to know the position of the item, you can always go with implementation of hashCode and equals in the model class of the list item used in recyclerview adapter.

Implement hashcode and equals method to get the position for the required model object.

Example :

public class Employee {
    protected long   employeeId;
    protected String firstName;
    protected String lastName;

    public boolean equals(Object o){
    if(o == null)                return false;
    if(!(o instanceof) Employee) return false;

    Employee other = (Employee) o;
    if(this.employeeId != other.employeeId)      return false;
    if(! this.firstName.equals(other.firstName)) return false;
    if(! this.lastName.equals(other.lastName))   return false;

    return true;
  }

  public int hashCode(){
    return (int) employeeId;
  }
}

// To get the index of selected item which triggered async task :
int itemIndex = EmployeeList.indexOf(selectedEmployeeModel);
recyclerView.scrollToPosition(itemIndex);