To add data to RecyclerView at runtime follow the steps mentioned below:-

1) Start a new project and add support library dependency <compile 'com.android.support:recyclerview-v7'>.

2) Declare layout for your activity(MainActivity) and add the RecyclerView to this Layout.

activity_main.xml

 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools" 
    android:layout_width="match_parent"
    android:layout_height="match_parent" 
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:orientation="vertical"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity"
    android:background="#000">

    <Button
        android:id="@+id/ADDButton"
        android:layout_gravity="center"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="ADD"
        />
<android.support.v7.widget.RecyclerView
    android:id="@+id/RecyclerView"
    android:layout_height="match_parent"
    android:layout_width="match_parent"/>
</LinearLayout>

3) Now initialize the adapter and widgets in MainActivity.java file.

MainActivity.java

import android.app.Activity;
import android.app.Dialog;
import android.content.Context;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.view.View.OnClickListener;
import android.widget.Toast;

import java.util.ArrayList;

public class MainActivity extends Activity {

    private Button mAddButton;
    final Context context=this;
    private ArrayList<FeedItem> feedlist;
    private MyAdapter myAdapter;
    private RecyclerView mRecyclerView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        IntialDeclaration();
    }

    public void IntialDeclaration()
    {
        mRecyclerView=(RecyclerView)findViewById(R.id.RecyclerView);
        mRecyclerView.setLayoutManager(new LinearLayoutManager(MainActivity.this));
        mAddButton=(Button)findViewById(R.id.ADDButton);
        mAddButton.setOnClickListener(mClickListener);
        feedlist = new ArrayList<>();
    }
    View.OnClickListener mClickListener=new OnClickListener() {
        @Override
        public void onClick(View v) {

             final Dialog dialog = new Dialog(context);
             dialog.setContentView(R.layout.dialog_layout);
             dialog.setTitle(" Enter New Tuple");
             final TextView mMailEditText, mNameEditText;
             Button mADDButton, mDismiss;
             mMailEditText = (EditText) dialog.findViewById(R.id.MailEditText);
             mNameEditText = (EditText) dialog.findViewById(R.id.NameEditText);
             mADDButton = (Button) dialog.findViewById(R.id.AddButton);
            mADDButton.setOnClickListener(new OnClickListener() {
                @Override
                public void onClick(View v) {
                    boolean a=false;
                    boolean b=true;
                    boolean c=true;
                    String MAIL=mMailEditText.getText().toString();
                    String NAME=mNameEditText.getText().toString();
                    String EMAIL_PATTERN = "^[_A-Za-z0-9-\\+]+(\\.[_A-Za-z0-9-]+)*@" + "[A-Za-z0-9-]+(\\.[A-Za-z0-9]+)*(\\.[A-Za-z]{2,})$";
                    if(NAME.equals(""))
                    {
                        c=false;
                        Toast.makeText(MainActivity.this,"please insert Name",Toast.LENGTH_LONG).show();
                    }
                    if(MAIL.equals(""))
                    {
                        b=false;
                        Toast.makeText(MainActivity.this,"please insert m@il id",Toast.LENGTH_LONG).show();
                    }
                    else if(MAIL.matches(EMAIL_PATTERN))
                    {
                        a=true;

                    }
                    else {
                        Toast.makeText(MainActivity.this,"invalid em@il id",Toast.LENGTH_LONG).show();
                    }
                    if(a&&b&&c) {
                        ArrayList feed = new ArrayList<FeedItem>();
                        FeedItem Feed = new FeedItem(NAME, MAIL);
                        myAdapter = new MyAdapter(MainActivity.this, feedlist);
                        mRecyclerView.setAdapter(myAdapter);
                        feedlist.add(Feed);
                        dialog.dismiss();
                    }
                }
            });
             mDismiss = (Button) dialog.findViewById(R.id.DismissButton);
             mDismiss.setOnClickListener(new OnClickListener() {
                 @Override
                 public void onClick(View v) {
                     dialog.dismiss();
                 }
             });
             dialog.show();
         }

    };
}

4) Create a layout that will be inflated on RecyclerView .

recycle_view_layout.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_marginTop="20dp"
    android:layout_marginRight="10dp"
    android:layout_marginLeft="10dp"
    android:background="#734ff3"
    android:layout_marginBottom="20dp"
    >

    <LinearLayout
        android:layout_marginTop="10dp"
        android:layout_marginLeft="10dp"
        android:id="@+id/LinearLayout"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical">
        <TextView
            android:id="@+id/NameTextView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textColor="#000"
            android:textSize="24dp"
            android:text="Name"/>
        <TextView
            android:textColor="#000"
            android:id="@+id/MailTextView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textSize="17dp"
            android:text="m@il Id"/>
    </LinearLayout>
    <ImageView
        android:layout_marginRight="10dp"
        android:layout_marginTop="10dp"
        android:id="@+id/DeleteIcon"
        android:layout_width="60dp"
        android:layout_height="50dp"
        android:layout_alignParentRight="true"
        android:src="@drawable/delete"/>

   <View
       android:layout_alignBottom="@+id/LinearLayout"
       android:layout_width="match_parent"
       android:layout_height="2dp"
       android:background="#fff"
       android:layout_marginRight="20dp"
       android:layout_marginLeft="20dp"
      android:layout_marginTop="30dp"/>


</RelativeLayout>

5) I am creating another layout for dialog from where data will be inserted into RecyclerView.

dialog_layout.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"
    >
    <EditText
        android:id="@+id/NameEditText"
        android:layout_marginTop="20dp"
        android:layout_marginLeft="15dp"
        android:layout_marginRight="15dp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Name"
        android:singleLine="true"/>
    <EditText
        android:id="@+id/MailEditText"
        android:layout_marginTop="20dp"
        android:layout_marginLeft="15dp"
        android:layout_marginRight="15dp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="m@il-id"
        android:singleLine="true"/>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">
        <Button
            android:id="@+id/AddButton"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="ADD"
            android:layout_marginLeft="50dp"
            />
        <Button
            android:id="@+id/DismissButton"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Dismiss"
            android:layout_marginLeft="30dp"
            />

    </LinearLayout>
</LinearLayout>

6) Create a custom adapter that will be used for RecyclerView.

MyAdapter.java

import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;
import java.util.ArrayList;


public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {
    private ArrayList<FeedItem> feedItemList;
private Context mContext;
    public MyAdapter(Context context,ArrayList<FeedItem>feedItemList) {
        this.feedItemList=feedItemList;
    this.mContext=context;
    }

    // Create new views (invoked by the layout manager)
    @Override
    public MyAdapter.ViewHolder onCreateViewHolder(ViewGroup parent,
                                                   int viewType) {
        // create a new view
        View itemLayoutView = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.recycle_view_layout, null);

        // create ViewHolder

        ViewHolder viewHolder = new ViewHolder(itemLayoutView);
        return viewHolder;
    }

    // Replace the contents of a view (invoked by the layout manager)
    @Override
    public void onBindViewHolder(ViewHolder viewHolder, int position) {

        // - get data from your itemsData at this position
        // - replace the contents of the view with that itemsData

        viewHolder.mMailTextView.setText(feedItemList.get(position).getMAIL());
        viewHolder.mNameTextView.setText(feedItemList.get(position).getNAME());



    }

    // inner class to hold a reference to each item of RecyclerView
    public static class ViewHolder extends RecyclerView.ViewHolder {

        public TextView mNameTextView,mMailTextView;
        public ImageView imgViewIcon;

        public ViewHolder(View itemLayoutView) {
            super(itemLayoutView);
            mNameTextView = (TextView) itemLayoutView.findViewById(R.id.NameTextView);
            mMailTextView=(TextView)itemLayoutView.findViewById(R.id.MailTextView);
            imgViewIcon = (ImageView) itemLayoutView.findViewById(R.id.DeleteIcon);

        }
    }


    // Return the size of your itemsData (invoked by the layout manager)
    @Override
    public int getItemCount() {

        return feedItemList.size();
    }
}

7) I am using Getter and setter java file to retrieve data from dialog box and fetch data to RecyclerView custom Adapter.

Feeditem.java

   public class FeedItem {
    private String NAME;
    private String MAIL;
     FeedItem(String NAME,String MAIL)
    {
        this.MAIL=MAIL;
        this.NAME=NAME;
    }
    public String getNAME()
    {
        return NAME;
    }
    public void setNAME (String NAME)
    {
        this.NAME=NAME;
    }
    public String getMAIL()
    {
        return MAIL;
    }
    public void setMAIL(String MAIL)
    {
        this.MAIL=MAIL;
    }
}