Easy Implementation of RecyclerView custom onItemClickListener

README.md

#The Problem In the way of replacing ListViews with RecyclerView I hit this obstacle where there is no onItemClickListener in RecyclerView ??? And when googled, I found almost all the posts saying we have to implement this using the GestureDetector. And some of them had used interfaces which is what I too thought of using in the first place. But even they were so much confusing and complex to understand.

#Solution

Prerequisites

1. Interfaces (Donot worry if you never used one. But they are very simple concept) - CustomItemClickListener.java
2. ViewHolder Adapter - ItemsListAdapter.java
3. ViewHolder Item Class - ItemsListSingleItem.java
4. The RecyclerView Itself - ItemsList (See Setting up the RecyclerView)

Solving the problem

Consider for example you have a list of thumbnails and a title to be listed. I would do the following to keep stuff simple and working. :)

Checkout the sample project here

activity_list.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/items_list"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

</LinearLayout>

CustomItemClickListener.java

public interface CustomItemClickListener {
    public void onItemClick(View v, int position);
}

ItemsListAdapter.java

public class ItemsListAdapter extends RecyclerView.Adapter<ItemsListAdapter.ViewHolder> {
    ArrayList<ItemListSingleItem> data;

    Context mContext;
    CustomItemClickListener listener;

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View mView = LayoutInflater.from(parent.getContext()).inflate(R.layout.items_list_single_item, parent, false);
        final ViewHolder mViewHolder = new ViewHolder(mView);
        mView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                listener.onItemClick(v, mViewHolder.getPosition());
            }
        });
        return mViewHolder;
    }

    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        holder.itemTitle.setText(Html.fromHtml(data.get(position).getTitle()));
        if (!TextUtils.isEmpty(data.get(position).getThumbnailURL())) {
          // I Love picasso library :) http://square.github.io/picasso/
            Picasso.with(mContext).load(data.get(position).getThumbnailURL()).error(R.drawable.ic_no_image).
                    placeholder(R.drawable.ic_no_image).
                    transform(new RoundedCornersTransformation(5, 0)).
                    into(holder.thumbnailImage);
        } else {
            holder.thumbnailImage.setImageResource(R.drawable.ic_no_image);
        }
    }


    @Override
    public int getItemCount() {
        return data.size();
    }

    public ItemsListAdapter(Context mContext, ArrayList<ItemsListSingleItem> data, CustomItemClickListener listener) {
        this.data = data;
        this.mContext = mContext;
        this.listener = listener;
    }

    public static class ViewHolder extends RecyclerView.ViewHolder {
        public TextView itemTitle;
        public ImageView thumbnailImage;

        ViewHolder(View v) {
            super(v);
            itemTitle = (TextView) v
                    .findViewById(R.id.post_title);
            thumbnailImage = (ImageView) v.findViewById(R.id.post_thumb_image);
        }
    }
}

ItemsListSingleItem.java

public class ItemsListSingleItem {
    private String title,thumbnailURL;
    /**
     * Just for the sake of internal reference so that we can identify the item.
     */
    long id;

    /**
     *
     * @param id
     * @param title
     * @param thumbnailURL
     */
    public ItemsListSingleItem(long id, String title, String thumbnailURL) {
        this.id = id;
        this.title = title;
        this.thumbnailURL = thumbnailURL;
    }

    public String getTitle() {
        return title;
    }

    public long getID() {
        return id;
    }

    public String getThumbnailURL() {
        return thumbnailURL;
    }
}

ListActivity.java

public class HomeActivity extends AppCompatActivity{
    RecyclerView itemsList;
    ItemsListAdapter adapter;
    ArrayList<ItemsListSingleItem> data = new ArrayList<>();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_list);
      
      itemsList = (RecyclerView) getView().findViewById(R.id.items_list);
      itemsList.setHasFixedSize(true);
      mLinearLayoutManager = new LinearLayoutManager(this);
      itemsList.setLayoutManager(mLinearLayoutManager);

      //let us add some items into the list
      data.add(
        new ItemsListSingleItem(
        1,
        "First Item",
        "www.someUrlToMyThumbnailImage1"
      ));
                   
      data.add(
        new ItemsListSingleItem(
        2,
        "Second Item",
        "www.someUrlToMyThumbnailImage2"
      ));
      
      adapter = new ItemsListAdapter(getActivity(), data, new CustomItemClickListener() {
        @Override
        public void onItemClick(View v, int position) {
            Log.d(TAG, "clicked position:" + position);
            long postId = data.get(position).getID();
            // do what ever you want to do with it
        }
      });
      itemsList.setAdapter(adapter);
    }
}

Good idea!