Why kotlin gradle plugin cannot build with 1.8 target?

Question

I have the simplest gradle project configured using intellij for kotlin 1.2.10. Here is my build.gradle file:

buildscript {
    ext.kotlin_version = '1.2.10'

    repositories {
        mavenCentral()
    }
    dependencies {
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
    }
}

group 'com.ali'
version '1.0-SNAPSHOT'

apply plugin: 'java'
apply plugin: 'kotlin'

sourceCompatibility = 1.8

repositories {
    mavenCentral()
}

dependencies {
    compile "org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version"
    testCompile group: 'junit', name: 'junit', version: '4.12'
}

compileKotlin {
    kotlinOptions.jvmTarget = "1.8"
}
compileTestKotlin {
    kotlinOptions.jvmTarget = "1.8"
}

And I have a simple java interface:

public interface MyMath {
    static int myAbs(int input) {
        return Math.abs(input);
    }
}

When I import this interface and try to call myAbs method it fails with this error:

Error:(6, 12) Kotlin: Calls to static methods in Java interfaces are prohibited in JVM target 1.6. Recompile with '-jvm-target 1.8'

I have created an intellij kotlin app and it was working correctly. Is it a bug in new Kotlin gradle plugin?

Yes, and this problem only happens when I build the project in intellij. gradle in terminal works fine! — alisabzevari, Feb 04 '18 at 10:24
What is the IDE plugin version that you use? I could not reproduce the error with the 1.2.21 plugin. If that happens with the newer Gradle & IDE plugin versions as well, you could file an issue at [kotl.in/issue](https://kotl.in/issue) and describe the exact steps that lead to the error. — hotkey, Feb 04 '18 at 11:11

score 199 · Answer 1 · edited Mar 21 '19 at 15:21

199

I think this could be helpful for those using Android Studio 3.2 on Mac.

To change the Kotlin Compiler Target JVM version you should go to Android Studio -> Preferences -> Kotlin Compiler and then change the Target JVM version choosing from the dropdown.

Anyway, I'm still getting the following error

Calls to static methods in Java interfaces are prohibited in JVM target 1.6. Recompile with '-jvm-target 1.8'

SOLVED

Adding the following to my build.gradle solved the problem:

android {
    kotlinOptions {
        jvmTarget = '1.8'
    }
}

About this and other Gradle configuration options: https://kotlinlang.org/docs/reference/using-gradle.html

With Kotlin Gradle DSL:

import org.jetbrains.kotlin.gradle.dsl.KotlinJvmOptions

(kotlinOptions as KotlinJvmOptions).apply {
    jvmTarget = JavaVersion.VERSION_1_8.toString()
}

edited Mar 21 '19 at 15:21

EpicPandaForce

79,669
27
256
428

answered Sep 28 '18 at 19:54

Jairo Lozano

3,883
3
20
29

23

For Android projects, the Kotlin compiler target JVM version needs to be changed in build.gradle, not in the Android Studio preferences. Changes in the Android Studio preferences will not affect command-line builds. – yole Sep 28 '18 at 20:03
If someone gets the reason behind this error then please leave a comment tagging me. – Neeraj Sewani Jul 22 '19 at 18:55
Works for Android Studio 3.5. – Julian A. Sep 19 '19 at 02:15
2

Cool, it helps! And it's `app`'s gradle btw. – Wesely Jan 23 '20 at 17:47
2

Is it possible to set this at the root build.gradle file? It's tedious managing this across modules in a multi-module project. – robotsquidward Feb 03 '20 at 17:09
Is there a way to set 1.8 as default? – Abhishek Saxena Jun 11 '20 at 19:24
not work i s have set it – Yogi Arif Widodo Feb 20 '22 at 04:34

score 92 · Accepted Answer · answered Feb 04 '18 at 11:15

92

It turned out that it was my kotlin compiler configuration in intellij settings. In Settings > Build, Execution, Deployment > Compiler > Kotlin Compiler a setting called Target JVM version should have been set to 1.8.

answered Feb 04 '18 at 11:15

alisabzevari

8,008
6
43
67

7

In my version it's in `Settings -> Other Settings -> Kotlin Compiler -> Target JVM Version` – ElyashivLavi Feb 12 '18 at 11:56
7

But even when set to 1.8, I still get `Calls to static methods in Java interfaces are prohibited in JVM target 1.6. Recompile with '-jvm-target 1.8'` – ElyashivLavi Feb 12 '18 at 13:31
I don't have `Other Settings` in mine! – alisabzevari Feb 14 '18 at 09:21
40

In my case I fix it in `Project Structure -> Facets -> Kotling -> Target Platform` – Pablo Bastidas May 03 '18 at 19:17
Actually, I set all of the above and no more message... yet. IJ 2018.1.5 Kotlin 1.2.50. – softjake Jun 27 '18 at 16:33

score 25 · Answer 3 · answered Jan 18 '20 at 08:28

25

There is a gradle property used by Kotlin plugin which can be used. When you add

kotlin.setJvmTargetFromAndroidCompileOptions = true

to your gradle.properties file. When you have this configuration on your build.config

android{
  compileOptions {
      sourceCompatibility = 1.8
      targetCompatibility = 1.8
  }
}

problem sould be solved.

answered Jan 18 '20 at 08:28

Karol Kulbaka

1,136
11
21

2

The project I was working on had `sourceCompatibility ` & `targetCompatibility` configured but adding the `kotlin.setJvmTargetFromAndroidCompileOptions = true` solved the problem for me – Fdo Apr 23 '20 at 13:38
where is i put the kotlin.setJvmTargetFromAndroidCompileOptions = true code ? more spesific pls – Yogi Arif Widodo Feb 20 '22 at 04:47
in gradle.properties at any level – Karol Kulbaka Feb 21 '22 at 07:16

score 24 · Answer 4 · answered Aug 27 '19 at 11:35

24

Please check if you have the following three stuff set in idea:

kotlin options in build.gradle

    kotlinOptions {
        jvmTarget = '1.8'
    }

Check the relevant Idea preferences
Check the project Facets

answered Aug 27 '19 at 11:35

Antal Attila

588
6
18

score 15 · Answer 5 · answered Nov 11 '19 at 03:05

15

//Just add the below code in your Build gradle(Module:app)

compileOptions {
    sourceCompatibility = 1.8
    targetCompatibility = 1.8
}
tasks.withType(org.jetbrains.kotlin.gradle.tasks.KotlinCompile).all {
    kotlinOptions {
        jvmTarget = "1.8"
    }
 }

answered Nov 11 '19 at 03:05

Sivakumar Ramadas

159
1
2

Yep, this helped me. Thanks. – Yura Galavay Mar 29 '21 at 21:24

score 4 · Answer 6 · answered Aug 16 '20 at 09:21

4

This worked for me in Gradle with Kotlin DSL:

import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
val compileKotlin: KotlinCompile by tasks
compileKotlin.kotlinOptions.jvmTarget = JavaVersion.VERSION_11.toString()

answered Aug 16 '20 at 09:21

Ayush

3,695
1
32
42

score 3 · Answer 7 · answered Dec 07 '18 at 20:27

3

This is also set in project settings, under Project Settings > Modules > Kotlin. This was my specific problem... literally the last thing I tried.

answered Dec 07 '18 at 20:27

Tim Keating

6,443
4
47
53

score 3 · Answer 8 · answered Dec 07 '20 at 10:27

3

Settings > Build, Execution, Deployment > Compiler > Kotlin Compiler a setting called Target JVM version should have been set to 1.8.

answered Dec 07 '20 at 10:27

Seroj Grigoryan

159
1
2

score 1 · Answer 9 · answered Feb 04 '18 at 10:30

1

Not quite sure why this works, but you could try changing the setting in the Idea itself. Since Gradle from the command line works, but not when building from IntelliJ this is probably the root.

Go to File -> Project Structure. Go to the Project tab and make sure Project SDK is 8 (or newer) and set the Project language level to Java 8

The config in there seems to override Gradle for some reason, so changing it should work

answered Feb 04 '18 at 10:30

Zoe

27,060
21
118
148

It is 8 in my intellij! – alisabzevari Feb 04 '18 at 10:47
Try invalidating the caches and restarting – Zoe Feb 04 '18 at 10:52
Didn't work. I have a project created with older intellij (current is 2017.3.4). The old one is working. I am comparing .idea folders of two project with each other. Does it make sense? – alisabzevari Feb 04 '18 at 11:02
3

I had the same error on a maven project. Just solved adding 1.8 to the properties section. Take a look here https://youtrack.jetbrains.com/issue/KT-17492 for more info – Paolo Aug 31 '18 at 14:51
The "Project language level" setting controls how Java source code is highlighted in the IDE. It has no impact on Kotlin compilation whatsoever. – yole Sep 28 '18 at 20:04

score 1 · Answer 10 · answered Apr 05 '22 at 11:43

Try this code, it solved my problem. I had a problem inViewModel Factory. //Just add the below code in your Build gradle(Module:app)

Error "Inheritance from an interface with '@JvmDefault' members is only allowed with -Xjvm-default option"

    kotlinOptions {
    freeCompilerArgs = ['-Xjvm-default=compatibility']
    jvmTarget = '1.8'
}

score 0 · Answer 11 · answered Oct 31 '18 at 05:18

In my case, I tried all @alisabzevari options including given in comment, but It didn't work,

my mistake I added java file also in src/<sourcset_name>kotlin/ folder, later I converted java file to kotlin file. and Voila! It works.

May be it will help somebody.

score 0 · Answer 12 · answered May 27 '21 at 07:13

0

solved it by editing build.gradle.kts

val compileKotlin: KotlinCompile by tasks
compileKotlin.kotlinOptions.jvmTarget = "1.8"

answered May 27 '21 at 07:13

Jim

1,123
13
29

Why kotlin gradle plugin cannot build with 1.8 target?

12 Answers12

Linked