A very simple example of Android RecyclerView

In this post, we will create a basic item list using RecyclerView and implementing the View.OnClickListener. It will display a list of TextViews with item number, when an row is clicked, a log message will be printed with the item number of the view that’s clicked.

Add the RecyclerView support library in your gradle dependencies

compile 'com.android.support:recyclerview-v7:23.1.0'

activity_main.xml, layout file for the main activity which will hold the RecyclerView in this example. You can replace the default generated code with the following.
[code language=”xml”]
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
>
<android.support.v7.widget.RecyclerView
android:id="@+id/item_list"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:scrollbars="vertical"
/>
</LinearLayout>
[/code]

list_item.xml, layout file for each of the row in the RecyclerView.
[code language=”xml”]
<?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:layout_height="match_parent">
<TextView
android:id="@+id/row_item"
android:layout_width="match_parent"
android:layout_height="50dp"
android:gravity="center"/>
</LinearLayout>
[/code]

Item.java, the item class for each item in the list, it can be any other custom class. For demonstration purpose, this class is very simple, only have one field, the name.
[code language=”java”]
public class Item {

private String name;

public Item(String n) {
name = n;
}
public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}
}
[/code]

ItemArrayAdapter.java, this is the adapter for the RecyclerView. This adapter is also a very simple and contains only the minium required methods, constructor and ViewHolder.
[code language=”java”]
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import com.codexpedia.list.viewholder.R;
import java.util.ArrayList;

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

//All methods in this adapter are required for a bare minimum recyclerview adapter
private int listItemLayout;
private ArrayList<Item> itemList;
// Constructor of the class
public ItemArrayAdapter(int layoutId, ArrayList<Item> itemList) {
listItemLayout = layoutId;
this.itemList = itemList;
}

// get the size of the list
@Override
public int getItemCount() {
return itemList == null ? 0 : itemList.size();
}

// specify the row layout file and click for each row
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(listItemLayout, parent, false);
ViewHolder myViewHolder = new ViewHolder(view);
return myViewHolder;
}

// load data in each row element
@Override
public void onBindViewHolder(final ViewHolder holder, final int listPosition) {
TextView item = holder.item;
item.setText(itemList.get(listPosition).getName());
}

// Static inner class to initialize the views of rows
static class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
public TextView item;
public ViewHolder(View itemView) {
super(itemView);
itemView.setOnClickListener(this);
item = (TextView) itemView.findViewById(R.id.row_item);
}
@Override
public void onClick(View view) {
Log.d("onclick", "onClick " + getLayoutPosition() + " " + item.getText());
}
}
}
[/code]

MainActivity.java, the main activity, you can replace the default generated code in the MainActivity.java with the following.
[code language=”java”]
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.DefaultItemAnimator;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;

import com.codexpedia.list.viewholder.R;

import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {

RecyclerView recyclerView;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

// Initializing list view with the custom adapter
ArrayList <Item> itemList = new ArrayList<Item>();

ItemArrayAdapter itemArrayAdapter = new ItemArrayAdapter(R.layout.list_item, itemList);
recyclerView = (RecyclerView) findViewById(R.id.item_list);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
recyclerView.setItemAnimator(new DefaultItemAnimator());
recyclerView.setAdapter(itemArrayAdapter);

// Populating list items
for(int i=0; i<100; i++) {
itemList.add(new Item("Item " + i));
}

}

}
[/code]

Complete example in Github