Updating data in an Android RecyclerView

This is a repost of an answer I wrote on Stack Overflow.

There are two main things that I find helpful when exploring a new API: seeing examples (especially ones with pictures) and just trying out all the possibilities. This post will hopefully help you with that as you are learning how to update the adapter data in an Android RecyclerView. If you need help setting up the RecyclerView itself, then see this post or scroll down to the Code section below.

Overview

The process of modifying the adapter data includes two main steps every time:

The following examples will show how to do that.

Insert single item

Add “Pig” at index 2.

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

Insert multiple items

Insert three more animals at index 2.

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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 single item

Remove “Pig” from the list.

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

Remove multiple items

Remove “Camel” and “Sheep” from the list.

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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.

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data.clear();
adapter.notifyDataSetChanged();

Replace old list with new list

Clear the old list then add a new one.

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// 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.”

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

Move single item

Move “Sheep” from position 3 to position 1.

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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

Further study

Written by

A Flutter and Dart developer. Follow me on Twitter @suragch1 to get updates of new articles.

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