How to update RecyclerView Adapter Data?

问题:

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, then call adapter.notifyDataSetChanged() ; it did not work.

2. Create a new adapter, as others did, and it worked for them, but no 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?

---

Update: 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 parent layout.

回答1:

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

1) REMOVE: There are 4 steps to remove an item from a RecyclerView

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

These line of codes work for me.

2) UPDATE THE DATA: The only things I had to do is

mAdapter.notifyDataSetChanged();

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

回答2:

This is a general answer for future visitors. 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 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 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 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

回答3:

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.

回答4:

you have 2 options to do this: refresh UI from the adapter:

mAdapter.notifyDataSetChanged();

or refresh it from recyclerView itself:

recyclerView.invalidate();

回答5:

Another option is to use diffutil . It will compare the original list against the new list and use the new list as the update if there is a change.

Basically, we can use DiffUtil to compare the old data vs new data and let it call notifyItemRangeRemoved, and notifyItemRangeChanged and notifyItemRangeInserted on your behalf.

A quick example of using diffUtil instead of notifyDataSetChanged:

DiffResult diffResult = DiffUtil
                .calculateDiff(new MyDiffUtilCB(getItems(), items));

//any clear up on memory here and then
diffResult.dispatchUpdatesTo(this);

//and then, if necessary
items.clear()
items.addAll(newItems)

I do the calculateDiff work off the main thread in case it\'s a big list.

回答6:

Update Data of listview, gridview and recyclerview

mAdapter.notifyDataSetChanged();

or

mAdapter.notifyItemRangeChanged(0, itemList.size());

回答7:

I\'ve solved the same problem in a different way. I don\'t have data I waiting for it from the background thread so start with an emty list.

        mAdapter = new ModelAdapter(getContext(),new ArrayList<Model>());
   // then when i get data

        mAdapter.update(response.getModelList());
  //  and update is in my adapter

        public void update(ArrayList<Model> modelList){
            adapterModelList.clear(); 
            for (Product model: modelList) {
                adapterModelList.add(model); 
            }
           mAdapter.notifyDataSetChanged();
        }

That\'s it.

回答8:

The best and the coolest way to add new data to the present data is

 ArrayList<String> newItems = new ArrayList<String>();
 newItems = getList();
 int oldListItemscount = alcontainerDetails.size();
 alcontainerDetails.addAll(newItems);           
 recyclerview.getAdapter().notifyItemChanged(oldListItemscount+1, al_containerDetails);

回答9:

I found out that a really simple way to reload the RecyclerView is to just call

recyclerView.removeAllViews();

This will first remove all content of the RecyclerView and then add it again with the updated values.

回答10:

i got the answer after a long time

  SELECTEDROW.add(dt);
                notifyItemInserted(position);
                SELECTEDROW.remove(position);
                notifyItemRemoved(position);

回答11:

If nothing mentioned in the above comments is working for you. It might mean the problem lies somewhere else.

One place I found the solution was in the way I was setting the list to the adapter. In my activity the list was a instance variable and I was changing it directly when any data changed. Due to it being a reference variable there was something weird going on. So I changed the reference variable to a local one and used another variable to update data and then pass to addAll() function mentioned in above answers.

回答12:

These methods are efficient and good to start using a basic RecyclerView.

private List<YourItem> items;

public void setItems(List<YourItem> newItems)
{
    clearItems();
    addItems(newItems);
}

public void addItem(YourItem item, int position)
{
    if (position > items.size()) return;

    items.add(item);
    notifyItemInserted(position);
}

public void addMoreItems(List<YourItem> newItems)
{
    int position = items.size() + 1;
    newItems.addAll(newItems);
    notifyItemChanged(position, newItems);
}

public void addItems(List<YourItem> newItems)
{
    items.addAll(newItems);
    notifyDataSetChanged();
}

public void clearItems()
{
    items.clear();
    notifyDataSetChanged();
}

public void addLoader()
{
    items.add(null);
    notifyItemInserted(items.size() - 1);
}

public void removeLoader()
{
    items.remove(items.size() - 1);
    notifyItemRemoved(items.size());
}

public void removeItem(int position)
{
    if (position >= items.size()) return;

    items.remove(position);
    notifyItemRemoved(position);
}

public void swapItems(int positionA, int positionB)
{
    if (positionA > items.size()) return;
    if (positionB > items.size()) return;

    YourItem firstItem = items.get(positionA);

    videoList.set(positionA, items.get(positionB));
    videoList.set(positionB, firstItem);

    notifyDataSetChanged();
}

You can implement them inside of an Adapter Class or in your Fragment or Activity but in that case you have to instantiate the Adapter to call the notification methods. In my case I usually implement it in the Adapter.