activity_main.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"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:animateLayoutChanges="true"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <android.support.v7.widget.SearchView
        android:id="@+id/searchView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:iconifiedByDefault="false" />
    <TextView
        android:layout_marginStart="16dp"
        android:layout_marginEnd="16dp"
        android:textColor="@android:color/holo_red_dark"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/occurrenceTextView"/>
    <ScrollView
        android:clipToPadding="true"
        android:layout_margin="16dp"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <TextView

            android:textAppearance="@style/TextAppearance.AppCompat.Body1"
            android:id="@+id/textView"
            android:layout_width="match_parent"
            android:layout_height="wrap_content" />
    </ScrollView>

</LinearLayout>

MainActivity.kt

import android.app.Activity
import android.graphics.Color
import android.graphics.Paint
import android.os.Bundle
import android.support.v7.widget.SearchView
import android.text.SpannableString
import android.text.style.BackgroundColorSpan
import android.util.Log
import kotlinx.android.synthetic.main.activity_main.*
import android.text.Spanned


class MainActivity : Activity() {
    lateinit var data: String


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

        textView.text = data
        searchView.setOnQueryTextListener(object : SearchView.OnQueryTextListener {
            override fun onQueryTextSubmit(query: String?): Boolean {
                return false
            }

            override fun onQueryTextChange(newText: String): Boolean {
                highlightText(newText)
                return false
            }
        })
        occurrenceTextView.paintFlags = Paint.UNDERLINE_TEXT_FLAG
    }

    private fun highlightText(s: String) {
        var occurrence = 0
        val spannableString = SpannableString(textView.text)
        val backgroundColorSpans =
                spannableString.getSpans(0, spannableString.length, BackgroundColorSpan::class.java)
       backgroundColorSpans.forEach { spannableString.removeSpan(it) }

        var index = spannableString.toString().indexOf(s)
        while (index > 0) {
            occurrence += 1
            spannableString.setSpan(BackgroundColorSpan(Color.GREEN), index,
                    index + s.length, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE)
            index = spannableString.toString().indexOf(s, index + s.length)
        }
        textView.text = spannableString
        occurrenceTextView.text = "this word occurred $occurrence times"
    }

    private fun Any.log() =
            Log.d("MEGA", this.toString())

}