How to update RecyclerView Adapter Data?

I'm working with RecyclerView and both the remove and the update work well.

  1. Remove:

    There are four steps to remove an item from a RecyclerView

     list.remove(position);
     recycler.removeViewAt(position);
     mAdapter.notifyItemRemoved(position);
     mAdapter.notifyItemRangeChanged(position, list.size());
    

    These lines of code work for me.

  2. Update the data:

    The only things I had to do was:

     mAdapter.notifyDataSetChanged();
    

You had to do all of this in the Actvity/Fragment code, not in the RecyclerView Adapter code.


This is a general answer. The various ways to update the adapter data are explained. The process includes two main steps every time:

  1. Update the data set
  2. Notify the adapter of the change

Insert single item

Add "Pig" at index 2.

Insert single item
String item = "Pig";
int insertIndex = 2;
data.add(insertIndex, item);
adapter.notifyItemInserted(insertIndex);

Insert multiple items

Insert three more animals at index 2.

Insert multiple items
ArrayList<String> items = new ArrayList<>();
items.add("Pig");
items.add("Chicken");
items.add("Dog");
int insertIndex = 2;
data.addAll(insertIndex, items);
adapter.notifyItemRangeInserted(insertIndex, items.size());

Remove a single item

Remove "Pig" from the list.

Remove single item
int removeIndex = 2;
data.remove(removeIndex);
adapter.notifyItemRemoved(removeIndex);

Remove multiple items

Remove "Camel" and "Sheep" from the list.

Remove multiple items
int startIndex = 2; // inclusive
int endIndex = 4;   // exclusive
int count = endIndex - startIndex; // 2 items will be removed
data.subList(startIndex, endIndex).clear();
adapter.notifyItemRangeRemoved(startIndex, count);

Remove all items

Clear the whole list.

Remove all items
data.clear();
adapter.notifyDataSetChanged();

Replace old list with the new list

Clear the old list then add a new one.

Replace old list with new list
// clear old list
data.clear();

// add new list
ArrayList<String> newList = new ArrayList<>();
newList.add("Lion");
newList.add("Wolf");
newList.add("Bear");
data.addAll(newList);

// notify adapter
adapter.notifyDataSetChanged();

The adapter has a reference to data, so it is important that I didn't set data to a new object. Instead, I cleared the old items from data and then added the new ones.

Update single item

Change the "Sheep" item so that it says "I like sheep."

Update single item
String newValue = "I like sheep.";
int updateIndex = 3;
data.set(updateIndex, newValue);
adapter.notifyItemChanged(updateIndex);

Move a single item

Move "Sheep" from position 3 to position 1.

Move single item
int fromPosition = 3;
int toPosition = 1;

// update data array
String item = data.get(fromPosition);
data.remove(fromPosition);
data.add(toPosition, item);

// notify adapter
adapter.notifyItemMoved(fromPosition, toPosition);

Code

Here is the project code for your reference. The RecyclerView Adapter code can be found at this answer.

MainActivity.java

public class MainActivity extends AppCompatActivity implements MyRecyclerViewAdapter.ItemClickListener {

    List<String> data;
    MyRecyclerViewAdapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // data to populate the RecyclerView with
        data = new ArrayList<>();
        data.add("Horse");
        data.add("Cow");
        data.add("Camel");
        data.add("Sheep");
        data.add("Goat");

        // set up the RecyclerView
        RecyclerView recyclerView = findViewById(R.id.rvAnimals);
        LinearLayoutManager layoutManager = new LinearLayoutManager(this);
        recyclerView.setLayoutManager(layoutManager);
        DividerItemDecoration dividerItemDecoration = new DividerItemDecoration(recyclerView.getContext(),
                layoutManager.getOrientation());
        recyclerView.addItemDecoration(dividerItemDecoration);
        adapter = new MyRecyclerViewAdapter(this, data);
        adapter.setClickListener(this);
        recyclerView.setAdapter(adapter);
    }

    @Override
    public void onItemClick(View view, int position) {
        Toast.makeText(this, "You clicked " + adapter.getItem(position) + " on row number " + position, Toast.LENGTH_SHORT).show();
    }

    public void onButtonClick(View view) {
        insertSingleItem();
    }

    private void insertSingleItem() {
        String item = "Pig";
        int insertIndex = 2;
        data.add(insertIndex, item);
        adapter.notifyItemInserted(insertIndex);
    }

    private void insertMultipleItems() {
        ArrayList<String> items = new ArrayList<>();
        items.add("Pig");
        items.add("Chicken");
        items.add("Dog");
        int insertIndex = 2;
        data.addAll(insertIndex, items);
        adapter.notifyItemRangeInserted(insertIndex, items.size());
    }

    private void removeSingleItem() {
        int removeIndex = 2;
        data.remove(removeIndex);
        adapter.notifyItemRemoved(removeIndex);
    }

    private void removeMultipleItems() {
        int startIndex = 2; // inclusive
        int endIndex = 4;   // exclusive
        int count = endIndex - startIndex; // 2 items will be removed
        data.subList(startIndex, endIndex).clear();
        adapter.notifyItemRangeRemoved(startIndex, count);
    }

    private void removeAllItems() {
        data.clear();
        adapter.notifyDataSetChanged();
    }

    private void replaceOldListWithNewList() {
        // clear old list
        data.clear();

        // add new list
        ArrayList<String> newList = new ArrayList<>();
        newList.add("Lion");
        newList.add("Wolf");
        newList.add("Bear");
        data.addAll(newList);

        // notify adapter
        adapter.notifyDataSetChanged();
    }

    private void updateSingleItem() {
        String newValue = "I like sheep.";
        int updateIndex = 3;
        data.set(updateIndex, newValue);
        adapter.notifyItemChanged(updateIndex);
    }

    private void moveSingleItem() {
        int fromPosition = 3;
        int toPosition = 1;

        // update data array
        String item = data.get(fromPosition);
        data.remove(fromPosition);
        data.add(toPosition, item);

        // notify adapter
        adapter.notifyItemMoved(fromPosition, toPosition);
    }
}

Notes

  • If you use notifyDataSetChanged(), then no animation will be performed. This can also be an expensive operation, so it is not recommended to use notifyDataSetChanged() if you are only updating a single item or a range of items.
  • Check out DiffUtil if you are making large or complex changes to a list.

Further study

  • CodePath: Using the RecyclerView
  • Smart way to update RecyclerView using DiffUtil

This is what worked for me:

recyclerView.setAdapter(new RecyclerViewAdapter(newList));
recyclerView.invalidate();

After creating a new adapter that contains the updated list (in my case it was a database converted into an ArrayList) and setting that as adapter, I tried recyclerView.invalidate() and it worked.


You have two options to do this:

Refresh the UI from the adapter:

mAdapter.notifyDataSetChanged();

Or refresh it from the recyclerView itself:

recyclerView.invalidate();