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

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

Answer 2

//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"
    }
 }

Answer 3

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

Answer 4

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.