Unresolved reference: kotlinx - android-studio

Question

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:
I install the Kotlin plugin 1.0.0-beta-35950-IJ141-11
Create a new blank Android project
Convert the MainActivity file to Kotlin (via help->findaction->convert file to kotlin)
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)
}
}

Answer 1

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'

Answer 2

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.

Answer 3

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'

Answer 4

The buildscript block containing the kotlin-android-extensions dependency apparently needs to be in the app-module build.gradle, not in the top-level one.

Answer 5

I found why mine didn't work. My blocks were misplaced and by moving the buildscript{} block before the plugins as follow I got it working:
buildscript {
ext.kotlin_version = '1.0.0-beta-3595'
ext.anko_version = '0.8.1'
repositories {
jcenter()
}
dependencies {
classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
classpath "org.jetbrains.kotlin:kotlin-android-extensions:$kotlin_version"
}
}
apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
android {
compileSdkVersion 23
buildToolsVersion "23.0.2"
defaultConfig {
applicationId "com.kotlin"
minSdkVersion 15
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-v7:23.1.1'
compile "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
compile "org.jetbrains.anko:anko-sdk15:$anko_version"
compile "org.jetbrains.anko:anko-support-v4:$anko_version"
}

Answer 6

Removing the following import fixed the issue for me.
import android.R

Answer 7

add apply plugin: 'kotlin-android-extensions' in app/buildgradle.
if you have already added it, try to remove it and sync gradle, when sync is complete, then add it back and Sync Gradle again. This work for me.

Answer 8

The problem for me was the order in which I applied the plugins.
You must apply the kotlin-android plugin before the kotlin-android-extensions plugin
apply plugin: 'kotlin-android'
apply plugin: 'kotlin-android-extensions'

Answer 9

What worked for me in Android Studio 4.2 Beta 1 in macOS big sur to add id 'kotlin-android-extensions' to plugin section in app-level build.gradle file. So that it should look as follows.
plugins {
id 'com.android.application'
id 'kotlin-android'
id 'kotlin-android-extensions'
}
Then sync the project and it should work

Answer 10

With jetpack you have to use:
in the build.gradle (app)
buildFeatures {
dataBinding true
viewBinding true
}
plugins {
id 'kotlin-parcelize'
}
In activity_main.xml
<androidx.constraintlayout.widget.ConstraintLayout
tools:viewBindingIgnore="false">
In MainActivity.kt
import com.example.appname.databinding.ActivityMainBinding // ActivityMain is for main_activity.xml, and so on for any other activity
class MainActivity : AppCompatActivity() {
private lateinit var binding: ActivityMainBinding
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityMainBinding.inflate(layoutInflater)
val view = binding.root
setContentView(view)
binding.button.setOnClickListener {} // use binding.elementName
}
}

Answer 11

After applying the fixes mentioned above, I had to restart Android Studio to make it work.

Answer 12

If you are in the year 2021 then i guess most of the solutions you see here wont be of any help to you so try this instead
Go to your Module build.gradle file
add id 'kotlin-android-extensions' to the plugins object {}
Go to file the click on sync project with gradle files
Then go back and try to import kotlinx and that should work

Answer 13

In my case, adding:
apply plugin: 'kotlin-android'
apply plugin: 'kotlin-android-extensions'
at the end of the module-level build.grade fixed the issue.

Answer 14

Had same issue
plugins {
id 'com.android.application'
id 'kotlin-android'
apply plugin: 'kotlin-android-extensions'
apply plugin: "kotlin-kapt"
}
removed apply plugin: to idand restarted
plugins {
id 'com.android.application'
id 'kotlin-android'
id 'kotlin-android-extensions'
id "kotlin-kapt"
}

Answer 15

This is how it worked for me.
When I first configured Kotlin in Project, I selected the 1.1.2-3 version instead of 1.1.2-4 and added the following line in the build.gradle app file
apply plugin: 'kotlin-android-extensions'
after that I synced the build and it worked as expected.

Answer 16

I found out that I had support for C++ and Kotlin at the same time which was causing build problems.
When starting a new project, ensure C++ support is unchecked, and Kotlin support is checked. That fixed the problem for me.

Answer 17

In my case, I had put the code referring the view in a companion object. How silly..

Answer 18

For me the only thing that helped was to click "File" -> "Invalidate caches / Restart..."

Answer 19

in my case android studio line separator changed to CRLF( I am using macbook) windows settings.
when switch to CR fix my error

Answer 20

plugins {
id 'com.android.application'
id 'kotlin-android'
id 'kotlin-android-extensions'
}
For me I just had to add id 'kotlin-android-extensions' to plugins in build.gradle(Module:AppName.app)
And Sync it after that.

Answer 21

use this plug-in in your app project "Gradle script" folder in file "build.Gradle (Modules : progect_name)" :
"Kotlin-android-extensions"
then sync the projects.