How to update RecyclerView Adapter Data

Question

I am trying to figure out what is the issue with updating RecyclerView's Adapter.

After I get a new List of products, I tried to:

1. Update the ArrayList from the fragment where recyclerView is created, set new data to adapter, and then call adapter.notifyDataSetChanged(); it did not work.

2. Create a new adapter, as others did, and it worked for them, but there wasn't any change for me: recyclerView.setAdapter(new RecyclerViewAdapter(newArrayList))

3. Create a method in Adapter which updates the data as follows:

    public void updateData(ArrayList<ViewModel> viewModels) {     items.clear();     items.addAll(viewModels);     notifyDataSetChanged();  } 

   Then I call this method whenever I want to update the data list; it did not work.

4. To check if I can modify the recyclerView in any way, and I tried to remove at least an item:

     public void removeItem(int position) {      items.remove(position);      notifyItemRemoved(position);  } 

Everything remained as it was.

Here is my Adapter:

public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewAdapter.ViewHolder> implements View.OnClickListener {      private ArrayList<ViewModel> items;     private OnItemClickListener onItemClickListener;      public RecyclerViewAdapter(ArrayList<ViewModel> items) {         this.items = items;     }       public void setOnItemClickListener(OnItemClickListener onItemClickListener) {         this.onItemClickListener = onItemClickListener;     }      @Override     public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {         View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_recycler, parent, false);         v.setOnClickListener(this);         return new ViewHolder(v);     }      public void updateData(ArrayList<ViewModel> viewModels) {         items.clear();         items.addAll(viewModels);         notifyDataSetChanged();     }     public void addItem(int position, ViewModel viewModel) {         items.add(position, viewModel);         notifyItemInserted(position);     }      public void removeItem(int position) {         items.remove(position);         notifyItemRemoved(position);     }       @Override     public void onBindViewHolder(ViewHolder holder, int position) {         ViewModel item = items.get(position);         holder.title.setText(item.getTitle());         Picasso.with(holder.image.getContext()).load(item.getImage()).into(holder.image);         holder.price.setText(item.getPrice());         holder.credit.setText(item.getCredit());         holder.description.setText(item.getDescription());          holder.itemView.setTag(item);     }       @Override     public int getItemCount() {         return items.size();     }       @Override     public void onClick(final View v) {         // Give some time to the ripple to finish the effect         if (onItemClickListener != null) {             new Handler().postDelayed(new Runnable() {                 @Override                 public void run() {                     onItemClickListener.onItemClick(v, (ViewModel) v.getTag());                 }             }, 0);         }     }      protected static class ViewHolder extends RecyclerView.ViewHolder {         public ImageView image;         public TextView price, credit, title, description;          public ViewHolder(View itemView) {             super(itemView);             image = (ImageView) itemView.findViewById(R.id.image);             price = (TextView) itemView.findViewById(R.id.price);             credit = (TextView) itemView.findViewById(R.id.credit);             title = (TextView) itemView.findViewById(R.id.title);             description = (TextView) itemView.findViewById(R.id.description);         }     }      public interface OnItemClickListener {          void onItemClick(View view, ViewModel viewModel);      } } 

And I initiate RecyclerView as follows:

recyclerView = (RecyclerView) view.findViewById(R.id.recycler); recyclerView.setLayoutManager(new GridLayoutManager(getActivity(), 5)); adapter = new RecyclerViewAdapter(items); adapter.setOnItemClickListener(this); recyclerView.setAdapter(adapter); 

So, how do I actually update adapter data in order to display newly received items?

---

The issue was that the layout where gridView was looked as follows:

<?xml version="1.0" encoding="utf-8"?> <LinearLayout     xmlns:android="http://schemas.android.com/apk/res/android"     android:orientation="vertical"     android:layout_width="match_parent"     android:tag="catalog_fragment"     android:layout_height="match_parent">      <FrameLayout         android:orientation="vertical"         android:layout_width="match_parent"         android:layout_height="match_parent">          <android.support.v7.widget.RecyclerView             android:id="@+id/recycler"             android:layout_width="match_parent"             android:layout_height="match_parent"             android:clipToPadding="false"/>          <ImageButton             android:id="@+id/fab"             android:layout_gravity="top|end"             style="@style/FabStyle"/>      </FrameLayout> </LinearLayout> 

Then I just removed LinearLayout and made FrameLayout as the parent layout.

Answer 1

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.

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

Insert multiple items

Insert three more animals at index 2.

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.

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

Remove multiple items

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

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.

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

Replace old list with the new list

Clear the old list then add a new one.

// 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."

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.

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