Sample (fast scroll in RecyclerView)

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.RecyclerView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/recyclerView"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:fastScrollEnabled="true"
    app:fastScrollVerticalThumbDrawable="@drawable/fast_scroll_thumb2"
    app:fastScrollVerticalTrackDrawable="@drawable/fast_scroll_track2" />

fast_scroll_thumb.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:state_pressed="true">
        <shape android:shape="rectangle">
            <solid android:color="#f00" />
        </shape>
    </item>
    <item>
        <shape android:shape="rectangle">
            <solid android:color="#00f" />
        </shape>
    </item>
</selector>

fast_scroll_thumb2.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:state_pressed="true">
        <layer-list>
            <item android:width="8dp" android:gravity="end">
                <shape android:shape="rectangle">
                    <solid android:color="#f00" />
                </shape>
            </item>
            <item android:width="48dp">
                <shape android:shape="rectangle">
                    <solid android:color="@android:color/transparent" />
                </shape>
            </item>
        </layer-list>
    </item>
    <item>
        <layer-list>
            <item android:width="8dp" android:gravity="end">
                <shape android:shape="rectangle">
                    <solid android:color="#00f" />
                </shape>
            </item>
            <item android:width="48dp">
                <shape android:shape="rectangle">
                    <solid android:color="@android:color/transparent" />
                </shape>
            </item>
        </layer-list>
    </item>
</selector>

fast_scroll_track.xml

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <solid android:color="#0f0" />
</shape>

fast_scroll_track2.xml

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:width="8dp"
        android:gravity="end">
        <shape android:shape="rectangle">
            <solid android:color="#0f0" />
        </shape>
    </item>
    <item android:width="48dp">
        <shape android:shape="rectangle">
            <solid android:color="@android:color/transparent" />
        </shape>
    </item>
</layer-list>

MainActivity.kt

package com.nagopy.android.fastscrollingwithrecyclerviewsample

import android.os.Bundle
import android.support.v7.app.AppCompatActivity
import android.support.v7.widget.LinearLayoutManager
import android.support.v7.widget.RecyclerView
import android.view.LayoutInflater
import android.view.ViewGroup
import android.widget.TextView

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        findViewById<RecyclerView>(R.id.recyclerView).apply {
            setHasFixedSize(true)
            layoutManager = LinearLayoutManager(this@MainActivity)
            adapter = Adapter()
        }
    }

    class ViewHolder(val textView: TextView) : RecyclerView.ViewHolder(textView)

    class Adapter : RecyclerView.Adapter<ViewHolder>() {

        val items = ArrayList<String>().apply {
            for (i in 1..100) {
                add("No.$i")
            }
        }

        override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
            val v = LayoutInflater.from(parent.context)
                    .inflate(android.R.layout.simple_list_item_1, parent, false)
                    as TextView
            return ViewHolder(v)
        }

        override fun onBindViewHolder(holder: ViewHolder, position: Int) {
            holder.textView.text = items[position]
        }

        override fun getItemCount(): Int {
            return items.size
        }

    }
}