Android collapsing toolbar example in Kotlin

activity_main.xml

toolbar_menu.xml

MainActivity.kt

import android.os.Bundle
import android.support.design.widget.CollapsingToolbarLayout
import android.support.v7.app.AppCompatActivity
import android.support.v7.widget.Toolbar
import android.view.Menu
import android.view.MenuItem

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        val toolbar = findViewById(R.id.toolbar)
        setSupportActionBar(toolbar)

        val collapsingToolbar = findViewById(R.id.toolbar_layout)
        collapsingToolbar.title = "This is the title"
    }

    override fun onCreateOptionsMenu(menu: Menu): Boolean {
        // Inflate the menu; this adds items to the action bar if it is present.
        menuInflater.inflate(R.menu.toolbar_menu, menu)
        return true
    }

    override fun onOptionsItemSelected(item: MenuItem): Boolean {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        val id = item.itemId


        return if (id == R.id.action_settings) {
            true
        } else super.onOptionsItemSelected(item)
    }
}