Why kotlin gradle plugin cannot build with 1.8 target?

Gradle Problem Overview

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?

Gradle Solutions

Solution 1 - Gradle

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()
}

Solution 2 - Gradle

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.

Solution 3 - Gradle

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.

Solution 4 - Gradle

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

Solution 5 - Gradle

//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"
    }
 }

Solution 6 - Gradle

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()

Solution 7 - Gradle

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

Solution 8 - Gradle

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

Solution 9 - Gradle

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

Solution 10 - Gradle

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.

Solution 11 - Gradle

solved it by editing build.gradle.kts

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

Solution 12 - Gradle

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'
}

Content Type	Original Author	Original Content on Stackoverflow
Question	alisabzevari	View Question on Stackoverflow
Solution 1 - Gradle	Jairo Lozano	View Answer on Stackoverflow
Solution 2 - Gradle	alisabzevari	View Answer on Stackoverflow
Solution 3 - Gradle	Karol Kulbaka	View Answer on Stackoverflow
Solution 4 - Gradle	Antal Attila	View Answer on Stackoverflow
Solution 5 - Gradle	Sivakumar Ramadas	View Answer on Stackoverflow
Solution 6 - Gradle	Ayush	View Answer on Stackoverflow
Solution 7 - Gradle	Tim Keating	View Answer on Stackoverflow
Solution 8 - Gradle	Seroj Grigoryan	View Answer on Stackoverflow
Solution 9 - Gradle	Zoe stands with Ukraine	View Answer on Stackoverflow
Solution 10 - Gradle	dastan	View Answer on Stackoverflow
Solution 11 - Gradle	Jim	View Answer on Stackoverflow
Solution 12 - Gradle	Chirag Kumhar	View Answer on Stackoverflow