android-recyclerview-basic.md

title: Android: A basic RecyclerView tags:android,android-recyclerview

The RecyclerView is a more efficient version of GridView and ListView. With animated bells and whistles. And it works with CoordinatorLayout. You'll want to use it.

Although it's a large topic, here's a basic RecyclerView implementation. First the initialisation code and the XML:

RecyclerView rc = (RecyclerView) layout.findViewById(R.id.rec_view);
rc.setAdapter(new MyRecycler());
LinearLayoutManager mLayoutManager = new LinearLayoutManager(context);
rc.setLayoutManager(mLayoutManager);

The initialisation code is very similar to ListView's. But we have to set the LayoutManager.

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

The XML is just about the same as for a ListView.

The adapter is different, however:

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

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.listitem, parent, false);
        ViewHolder vh = new ViewHolder(v);
        return vh;
    }

    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        holder.textView.setText("Stuff, innit. " + position);
    }

    @Override
    public int getItemCount() {
        return 40;
    }

    public class ViewHolder extends RecyclerView.ViewHolder{
        private TextView textView;
        public ViewHolder(View itemView) {
            super(itemView);
            textView = (TextView) itemView.findViewById(R.id.listtext);
        }
    }
}

The first difference is it forces the ViewHolder pattern. The inner class is the generic class which extends the Adapter. It fetched View's from a passed-in View and makes such available as public fields.

Then onCreateViewHolder inflates a layout, and sets the ViewHolder with it. onBindViewHolder sets the holder with values, mostly likely values passed in to the adapter in a real world situation.