<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
  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"
  tools:context=".AboutActivity">

  <androidx.appcompat.widget.Toolbar
    android:id="@+id/toolbar"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:background="?attr/colorPrimary"
    android:minHeight="?attr/actionBarSize"
    android:theme="?attr/actionBarTheme"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

  <WebView
    android:id="@+id/about"
    android:layout_width="0dp"
    android:layout_height="0dp"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/toolbar" />
</androidx.constraintlayout.widget.ConstraintLayout>

package com.commonsware.todo

import android.content.Intent
import android.os.Bundle
import android.view.Menu
import android.view.MenuItem
import androidx.appcompat.app.AppCompatActivity
import com.commonsware.todo.databinding.ActivityMainBinding

class MainActivity : AppCompatActivity() {

  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)

    val binding = ActivityMainBinding.inflate(layoutInflater)

    setContentView(binding.root)
    setSupportActionBar(binding.toolbar)
  }

  override fun onCreateOptionsMenu(menu: Menu): Boolean {
    menuInflater.inflate(R.menu.actions, menu)

    return super.onCreateOptionsMenu(menu)
  }

  override fun onOptionsItemSelected(item: MenuItem) = when (item.itemId) {
    R.id.about -> {
      startActivity(Intent(this, AboutActivity::class.java))
      true
    }
    else -> super.onOptionsItemSelected(item)
  }
}

package com.commonsware.todo

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import com.commonsware.todo.databinding.ActivityAboutBinding

class AboutActivity : AppCompatActivity() {
  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)

    val binding = ActivityAboutBinding.inflate(layoutInflater)

    setContentView(binding.root)

    binding.toolbar.title = getString(R.string.app_name)
    binding.about.loadUrl("file:///android_asset/about.html")
  }
}