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         


        

Answer 1

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

Answer 2

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()

Answer 3

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.

Answer 4

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()
}

Answer 5

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.

Answer 6

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

1. kotlin options in build.gradle

    kotlinOptions {
        jvmTarget = '1.8'
    }

2. Check the relevant Idea preferences

3. Check the project Facets