Cannot create Kotlin object in Java (Android)

Question

I have an Android app written in Java and I am trying to write a new feature in Kotlin. So I added a new Kotlin file and IntelliJ offered to setup the project for Kotlin.

The issue is that when trying to create a Kotlin object in Java, compilation fails with

error: cannot find symbol constructor MyClassKt()

My Kotlin file (MyClass.kt):

 val SCREEN = 1;

 class MyClass() {
     fun hello(view: View) {
     } 
 }

In my app module:

implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"

In my project module:

 classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"

Invocation in Java:

 new MyClassKt();

Did you apply Kotlin plugin? The apply plugin: 'kotlin-android' on the top of your app module. — cycki
– cycki, Commented Oct 29, 2019 at 8:45
Thanks all! Updated the question, added the invocation, fixed the typos. — netcyrax
– netcyrax, Commented Oct 29, 2019 at 23:15

Harish Reddy · Accepted Answer · 2019-10-29 09:06:21Z

1

Make sure you have these plugin on top in the app gradle file

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

And inside dependencies, should be like

dependencies {
def kotlin_version= "2.2.1"
implementation"org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"       
}

edited Oct 29, 2019 at 9:06

answered Oct 29, 2019 at 8:57

Harish Reddy

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Comments

Sebastian Pakieła · Accepted Answer · 2019-10-29 09:55:42Z

0

Remove brackets from kotlin class definition.

class MyClassXD {
    fun hello(view: View) {
    }
}

Probably Java got wild when it saw brackets in classname.

answered Oct 29, 2019 at 9:55

Sebastian Pakieła

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3 Comments

Ircover Over a year ago

Brackets just says to add constructor without parameters, so it couldn't be a reason.

Sebastian Pakieła Over a year ago

No argument constructor is created by default if no other constructor defined, so you do not need them.

Ircover Over a year ago

Of course it is. And for example Android Studio will highlight it if you mention empty primary constructor, because it's useless to print that. I'm just trying to say it can't lead any error - it is just useless.

netcyrax · Accepted Answer · 2019-10-29 23:20:52Z

0

The problem was that Kotlin was creating a MyClassKt for the file (i.e. for accessing the SCREEN variable).

I just needed to use the normal class name and do new MyClass() (no Kt postfix).

Thanks all!

answered Oct 29, 2019 at 23:20

netcyrax

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