Unresolved reference: kotlinx

I am trying to try out Kotlin and the Kotlin Android extensions in Android Studio. I have tried this both in Android Studio v 1.5.1 on Ubuntu 14.04, and in Android Studio v 1.5.1 on OS X El Capitan with the same result.

Here is what I am doing:

1. I install the Kotlin plugin 1.0.0-beta-35950-IJ141-11
2. Create a new blank Android project
3. Convert the MainActivity file to Kotlin (via help->findaction->convert file to kotlin)
4. Configure the project for Kotlin

I then go into the generated content_main.xml file and add an id (hello) for the "Hello World!" TextView.

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="com.gmail.npnster.mykotlinfirstproject.MainActivity"
    tools:showIn="@layout/activity_main">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        android:id="@+id/hello"
        />
</RelativeLayout>  

Then in the converted MainActivity I add a line to set the TextView. (shown below). Android Studio then prompts me (via alt-enter) to insert this line (also shown below)

import kotlinx.android.synthetic.main.content_main.*

So at this point everything seems fine

but then when I try to compile this I get

Unresolved reference: kotlinx
Unresolved reference: kotlinx
Unresolved reference: hello

Notice that I did not install the Kotlin Android extensions plugin. As of a couple of days ago this is now supposed to be included in the main plug in and is marked as obsolete. (In fact if you try to install it when you have the latest plugin, nothing new is installed)

Anyone see what I am doing wrong?

MainActivity

import android.os.Bundle
import android.support.design.widget.FloatingActionButton
import android.support.design.widget.Snackbar
import android.support.v7.app.AppCompatActivity
import android.support.v7.widget.Toolbar
import android.view.View
import android.view.Menu
import android.view.MenuItem
import kotlinx.android.synthetic.main.content_main.*


class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        val toolbar = findViewById(R.id.toolbar) as Toolbar
        setSupportActionBar(toolbar)
        print("setting text view value to hey")
        hello.text = "hey"

        val fab = findViewById(R.id.fab) as FloatingActionButton
        fab.setOnClickListener { view -> Snackbar.make(view, "Replace this with your own action", Snackbar.LENGTH_LONG).setAction("Action", null).show() }
    }

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

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true
        }

        return super.onOptionsItemSelected(item)
    }
}

Add kotlin-android-extensions in our buildscript's dependencies:

1. In your project-level build.gradle

buildscript {
    dependencies {
        classpath "org.jetbrains.kotlin:kotlin-android-extensions:$kotlin_version"
    }
}

and apply the kotlin-android-extensions plugin:

2. In your module-level build.gradle

apply plugin: 'kotlin-android-extensions'

When you use Android Studio 2.0 and kotlin 1.0.1-2, you will come up with the same wrong. You cann't configure kotlin android extensions in your project's build.gradle, you need to configure and kotlin android extensions in every Module's build.gradle like this:

apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply plugin: 'kotlin-android-extensions'

buildscript {
    ext.kotlin_version = '1.0.1-2'
    repositories {
        jcenter()
    }
    dependencies {
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
        classpath "org.jetbrains.kotlin:kotlin-android-extensions:$kotlin_version"
    }
}

android {
    compileSdkVersion 23
    buildToolsVersion "24.0.0 rc2"

    defaultConfig {
        applicationId "com.dazd.kotlindemo"
        minSdkVersion 14
        targetSdkVersion 23
        versionCode 1
        versionName "1.0"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
    sourceSets {
       main.java.srcDirs += 'src/main/kotlin'
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    testCompile 'junit:junit:4.12'
    compile 'com.android.support:appcompat-v7:23.3.0'
    compile "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
}

Most importantly, even through the kotlin plugin included the kotlin android extension, you also need to configure the kotlin-android-extensions in your Module's bulid.gradle like this:

...
apply plugin: 'kotlin-android-extensions'
...
classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
classpath "org.jetbrains.kotlin:kotlin-android-extensions:$kotlin_version"

Of course, you could configure the kotlin plugin's classpath in your project's build.gradle.

I can't find it in the official documentation, but you must apply the plugin by adding the following to your build.gradle file:

apply plugin: 'kotlin-android-extensions'