Why doesn't RecyclerView have onItemClickListe

Question

I was exploring RecyclerView and I was surprised to see that RecyclerView does not have onItemClickListener(). Because RecyclerView extends

android.view.ViewGroup

and ListView extends

android.widget.AbsListView

. However I solved my problem by writing onClick in my RecyclerView.Adapter:

public static class ViewHolder extends RecyclerView.ViewHolder implements OnClickListener {

    public TextView txtViewTitle;
    public ImageView imgViewIcon;

    public ViewHolder(View itemLayoutView) {
        super(itemLayoutView);
        txtViewTitle = (TextView) itemLayoutView.findViewById(R.id.item_title);
        imgViewIcon = (ImageView) itemLayoutView.findViewById(R.id.item_icon);
    }

    @Override
    public void onClick(View v) {

    }
}

But still I want to know why Google removed onItemClickListener()?

Is there a performance issue or something else?

Answer 1

tl;dr 2016 Use RxJava and a PublishSubject to expose an Observable for the clicks.

public class ReactiveAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {
    String[] mDataset = { "Data", "In", "Adapter" };

    private final PublishSubject<String> onClickSubject = PublishSubject.create();

    @Override 
    public void onBindViewHolder(final ViewHolder holder, int position) {
        final String element = mDataset[position];

        holder.itemView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
               onClickSubject.onNext(element);
            }
        });
    }

    public Observable<String> getPositionClicks(){
        return onClickSubject.asObservable();
    }
}

Original Post:

Since the introduction of ListView, onItemClickListener has been problematic. The moment you have a click listener for any of the internal elements the callback would not be triggered but it wasn't notified or well documented (if at all) so there was a lot of confusion and SO questions about it.

Given that RecyclerView takes it a step further and doesn't have a concept of a row/column, but rather an arbitrarily laid out amount of children, they have delegated the onClick to each one of them, or to programmer implementation.

Think of Recyclerview not as a ListView 1:1 replacement but rather as a more flexible component for complex use cases. And as you say, your solution is what google expected of you. Now you have an adapter who can delegate onClick to an interface passed on the constructor, which is the correct pattern for both ListView and Recyclerview.

public static class ViewHolder extends RecyclerView.ViewHolder implements OnClickListener {

    public TextView txtViewTitle;
    public ImageView imgViewIcon;
    public IMyViewHolderClicks mListener;

    public ViewHolder(View itemLayoutView, IMyViewHolderClicks listener) {
        super(itemLayoutView);
        mListener = listener;
        txtViewTitle = (TextView) itemLayoutView.findViewById(R.id.item_title);
        imgViewIcon = (ImageView) itemLayoutView.findViewById(R.id.item_icon);
        imgViewIcon.setOnClickListener(this);
        itemLayoutView.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        if (v instanceof ImageView){
           mListener.onTomato((ImageView)v);
        } else {
           mListener.onPotato(v);
        }
    }

    public static interface IMyViewHolderClicks {
        public void onPotato(View caller);
        public void onTomato(ImageView callerImage);
    }

}

and then on your adapter

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

   String[] mDataset = { "Data" };

   @Override
   public MyAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
       View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.my_layout, parent, false);

       MyAdapter.ViewHolder vh = new ViewHolder(v, new MyAdapter.ViewHolder.IMyViewHolderClicks() { 
           public void onPotato(View caller) { Log.d("VEGETABLES", "Poh-tah-tos"); };
           public void onTomato(ImageView callerImage) { Log.d("VEGETABLES", "To-m8-tohs"); }
        });
        return vh;
    }

    // Replace the contents of a view (invoked by the layout manager) 
    @Override 
    public void onBindViewHolder(ViewHolder holder, int position) {
        // Get element from your dataset at this position 
        // Replace the contents of the view with that element 
        // Clear the ones that won't be used
        holder.txtViewTitle.setText(mDataset[position]);
    } 

    // Return the size of your dataset (invoked by the layout manager) 
    @Override 
    public int getItemCount() { 
        return mDataset.length;
    } 
  ...

Now look into that last piece of code: onCreateViewHolder(ViewGroup parent, int viewType) the signature already suggest different view types. For each one of them you'll require a different viewholder too, and subsequently each one of them can have a different set of clicks. Or you can just create a generic viewholder that takes any view and one onClickListener and applies accordingly. Or delegate up one level to the orchestrator so several fragments/activities have the same list with different click behaviour. Again, all flexibility is on your side.

It is a really needed component and fairly close to what our internal implementations and improvements to ListView were until now. It's good that Google finally acknowledges it.

Answer 2

Following up MLProgrammer-CiM's excellent RxJava solution

Consume / Observe clicks

ReactiveAdapter rxAdapter = new ReactiveAdapter();
rxAdapter.getPositionClicks().subscribe(mClickConsumer);

Consumer<String> mClickConsumer = new Consumer<String>() {
        @Override
        public void accept(@NonNull String element) throws Exception {
            Toast.makeText(getApplicationContext(), element +" was clicked", Toast.LENGTH_LONG).show();
        }
    };

RxJava 2.+

Modify the original tl;dr as:

public Observable<String> getPositionClicks(){
    return onClickSubject;
}

PublishSubject#asObservable() was removed. Just return the PublishSubject which is an Observable.

Answer 3

I use this method to start an Intent from RecyclerView:

@Override
 public void onBindViewHolder(ViewHolder viewHolder, int i) {

    final MyClass myClass = mList.get(i);
    viewHolder.txtViewTitle.setText(myclass.name);
   ...
    viewHolder.itemView.setOnClickListener(new View.OnClickListener() {
      @Override
       public void onClick(View v){
             Intent detailIntent = new Intent(mContext, type.class);                                                            
             detailIntent.putExtra("MyClass", myclass);
             mContext.startActivity(detailIntent);
       }
}
);

Answer 4

RecyclerView doesn't have an onItemClickListener because RecyclerView is responsible for recycling views (surprise!), so it's the responsibility of the view that is recycled to handle the click events it receives.

This actually makes it much easier to use, especially if you had items that can be clicked in multiple places.

---

Anyways, detecting click on a RecyclerView item is very easy. All you need to do is define an interface (if you're not using Kotlin, in which case you just pass in a lambda):

public class MyAdapter extends RecyclerView.Adapter<MyViewHolder> {
    private final Clicks clicks;

    public MyAdapter(Clicks clicks) {
        this.clicks = clicks;
    }

    private List<MyObject> items = Collections.emptyList();

    public void updateData(List<MyObject> items) {
        this.items = items;
        notifyDataSetChanged(); // TODO: use ListAdapter for diffing instead if you need animations
    }

    public interface Clicks {
        void onItemSelected(MyObject myObject, int position);
    }

    public class MyViewHolder extends RecyclerView.ViewHolder {
        private MyObject myObject;    

        public MyViewHolder(View view) {
            super(view);
            // bind views
            view.setOnClickListener((v) -> {
                int adapterPosition = getAdapterPosition();
                if(adapterPosition >= 0) {
                    clicks.onItemSelected(myObject, adapterPosition);
                }
            });
        }

        public void bind(MyObject myObject) {
            this.myObject = myObject;
            // bind data to views
        }
    }
}

Same code in Kotlin:

class MyAdapter(val itemClicks: (MyObject, Int) -> Unit): RecyclerView.Adapter<MyViewHolder>() {
    private var items: List<MyObject> = Collections.emptyList()

    fun updateData(items: List<MyObject>) {
        this.items = items
        notifyDataSetChanged() // TODO: use ListAdapter for diffing instead if you need animations
    }

    inner class MyViewHolder(val myView: View): RecyclerView.ViewHolder(myView) {
        private lateinit var myObject: MyObject

        init {
            // binds views
            myView.onClick {
                val adapterPosition = getAdapterPosition()
                if(adapterPosition >= 0) {
                    itemClicks.invoke(myObject, adapterPosition)
                }
            }
        }

        fun bind(myObject: MyObject) {
            this.myObject = myObject
            // bind data to views
        }
    }
}

Answer 5

Yes you can

public ViewHolder onCreateViewHolder(ViewGroup parent,int viewType) {

    //inflate the view 

    View view = LayoutInflator.from(parent.getContext()).inflate(R.layout.layoutID,null);

    ViewHolder holder = new ViewHolder(view);

    //here we can set onClicklistener
    view.setOnClickListener(new  View.OnClickListeener(){
        public void onClick(View v)
        {
            //action
        }
    });

return holder;

Answer 6

use PlaceHolderView

@Layout(R.layout.item_view_1)
public class View1{

    @View(R.id.txt)
    public TextView txt;

    @Resolve
    public void onResolved() {
        txt.setText(String.valueOf(System.currentTimeMillis() / 1000));
    }

    @Click(R.id.btn)
    public void onClick(){
        txt.setText(String.valueOf(System.currentTimeMillis() / 1000));
    }
}