String Attr

attrs.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <attr name="sample_attr_value" format="string"/>
</resources>

MainActivity.kt

package com.gabrielcosta.attrsample

import android.os.Bundle
import android.support.v7.app.AppCompatActivity
import android.util.TypedValue
import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity() {

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

        val typedValue = TypedValue()
        val resolveAttribute = theme.resolveAttribute(R.attr.sample_attr_value, typedValue, true)
        txt_sampleText.text = typedValue.string
    }
}

strings.xml

<resources>
    <string name="app_name">AttrSample</string>

    <string name="first_screen" >First Screen %s</string>
    <string name="second_screen" >Second Screen</string>
</resources>

styles.xml

<resources>

    <!-- Base application theme. -->
    <style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
        <!-- Customize your theme here. -->
        <item name="colorPrimary">@color/colorPrimary</item>
        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
        <item name="colorAccent">@color/colorAccent</item>
    </style>

    <style name="AppTheme.First">
        <item name="sample_attr_value">@string/first_screen</item>
    </style>

</resources>