Save last url used in an Android Webview as well as handle back button presses

MainActivity.kt

package com.pxelated.app

import android.app.Activity
import android.content.SharedPreferences
import android.os.Bundle
import android.support.v7.app.AppCompatActivity
import android.view.KeyEvent
import android.view.View
import android.webkit.WebView
import android.webkit.WebViewClient
import android.widget.TextView

class MainActivity : AppCompatActivity() {

    companion object {
        val LAST_URL = "lastUrl"
    }
    
    // Lazy load the webview with all of our configuration
    val webview: WebView by lazy {
        val webview = findViewById(R.id.webview) as WebView
        webview.settings.javaScriptEnabled = true
        webview.settings.domStorageEnabled = true
        webview.setWebChromeClient(WebChromeClient())
        webview.setWebViewClient(WebViewClient())

        webview
    }

    val prefs: SharedPreferences by lazy {
      applicationContext.getSharedPreferences(applicationContext.packageName, Activity.MODE_PRIVATE)
    }

    val lastOrMainUrl: String by lazy {
        prefs.getString(MainActivity.LAST_URL, BuildConfig.URL)
    }

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

    override fun onPause() {
        super.onPause()

        // Save the last url visited for this user
        prefs.edit()
                .putString(MainActivity.LAST_URL, webview.url)
                .commit() // .apply can also be used here _へ__(‾◡◝ )>
    }

    override fun onKeyDown(keyCode: Int, event: KeyEvent): Boolean {
        // Check if the key event was the Back button and if there's history
        if (keyCode == KeyEvent.KEYCODE_BACK && webview.canGoBack()) {
            webview.goBack()
            return true
        }

        // If it wasn't the Back key or there's no web page history, bubble up to the default
        // system behavior (exit the activity or go to previous activity)
        return super.onKeyDown(keyCode, event)
    }
}