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Click Listener for RecyclerView Adapter

DZone's Guide to

Click Listener for RecyclerView Adapter

In this tutorial, learn to create a click listener interface for RecyclerView for Android, with options like multiple listeners, and endless possibilities for the data.

· Mobile Zone
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There is a common pattern I use in all of my Android RecyclerView adapters to listen for click events on each item. I created an interface that is similar to the normal click listener, except it also has the position as a parameter.

public interface RecyclerViewClickListener {

    void onClick(View view, int position);
}

With this interface, I can set up a view holder class as a click listener, and pass in an instance of my interface. Then I set the view itself as a click listener and call my interface with the appropriate position.

public class RowViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {

    private RecyclerViewClickListener mListener;

    RowViewHolder(View v, RecyclerViewClickListener listener) {
        super(v);
        mListener = listener;
        v.setOnClickListener(this);
    }

    @Override
    public void onClick(View view) {
        mListener.onClick(view, getAdapterPosition());
    }
}

In your case you may not want to set the entire view as a click listener, maybe you have a button inside your layout. You can set it on that instead if you want, or add multiple listeners if you have multiple buttons for example. This is just a simple example to demonstrate how it works.

Now that I have a view holder, I can use it in my adapter.

public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {

        private RecyclerViewClickListener mListener;
        private List<Data> mDataset = new ArrayList<>();

        RecyclerViewAdapter(RecyclerViewClickListener listener) {
            mListener = listener;
        }

        public void updateData(List<Data> dataset) {
            mDataset.clear();
            mDataset.addAll(dataset);
            notifyDataSetChanged();
        }

        @Override
        public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
            Context context = parent.getContext();
            View v = LayoutInflater.from(context).inflate(R.layout.my_layout, parent, false);
            return new RowViewHolder(v, mListener);
        }

        @Override
        public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
            if (holder instanceof RowViewHolder) {
                RowViewHolder rowHolder = (RowViewHolder) holder;
                //set values of data here
            }
        }

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

I pass in my interface to the adapter so it can pass it to the view holder. There is only one instance of this listener, all of the views call back to the same instance. Since they are differentiated by the position being passed in, there‚Äôs no need to have multiple instances. I create this listener when the adapter is instantiated.

Lastly, here is an example of a fragment where I create this listener.

    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View v = inflater.inflate(R.layout.my_fragment, container, false);

        RecyclerView recyclerView =  (RecyclerView) v.findViewById(R.id.my_recyclerview);

        recyclerView.setHasFixedSize(true);
        LinearLayoutManager layoutManager = new LinearLayoutManager(getContext());
        recyclerView.setLayoutManager(layoutManager);

        RecyclerViewClickListener listener = (view, position) -> {
           Toast.makeText(getContext(), "Position " + position, Toast.LENGTH_SHORT).show();
        };
        RecyclerViewAdapter adapter = new RecyclerViewAdapter(listener);
        recyclerView.setAdapter(adapter);

        return v;
    }

I am simply toasting the position that was tapped on, but you could do anything with the data at this point. For example, you may have a list of notes, and tapping on one gives you its position in the list. With that, you can get the data object from the list and display the details of that note to the user.

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Topics:
mobile ,app development ,recyclerview ,tutorial ,android

Published at DZone with permission of Pierce Zaifman, DZone MVB. See the original article here.

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