[android] Cannot inline bytecode built with JVM target 1.8 into bytecode that is being built with JVM target 1.6

When trying to run the Example CorDapp (GitHub CorDapp) via IntelliJ, I receive the following error:

Cannot inline bytecode built with JVM target 1.8 into bytecode that is being built with JVM target 1.6

How can I modify the IntelliJ settings so that all the bytecode is built with the same JVM target?

app/build.gradle

android {
    ...
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }

    kotlinOptions {
        jvmTarget = JavaVersion.VERSION_1_8.toString()
    }
}

GL

Use Java 8 language features

you should configure something like as follows in build.gradle

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

please add this code to android section inside your app/build.gradle

compileOptions {
        sourceCompatibility = JavaVersion.VERSION_1_8
        targetCompatibility = JavaVersion.VERSION_1_8
    }
    kotlinOptions {
        jvmTarget = JavaVersion.VERSION_1_8
    }

In my case, just changingTarget JVM Version like this: File > Setting > Kotlin Compiler > Target JVM Version > 1.8 did not help. However, it does resolved compile time error. But failed at runtime.

I also had to add following in app build.gradle file to make it work.

 android {
     // Other code here...
     kotlinOptions {
        jvmTarget = "1.8"
     }
 }

When the other solutions did not work for you (Changing JVM version on Compiler settings and adding jvmTarget into your build.gradle), because of your .iml files trying to force their configurations you can change the target platform from Project Settings.

• Open File > Project Structure
• Go to Facets under Project Settings
  • If it is empty then click on the small + button
• Click on your Kotlin module/modules
• Change the Target Platform to JVM 1.8 (also it's better to check Use project settings option)

In my case this code did'n work until I move apply plugin: 'kotlin-android' from bottom to top.

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

android {
    ...
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }

    kotlinOptions {
        jvmTarget = "1.8"
    }
}

In Android Studio 4.3.2 adding through the below procedure is not working.

1. Open the IntelliJ preferences
2. Go to Build, Execution, Deployment > Compiler > Kotlin Compiler BUT Other Settings > Kotlin compiler if Android Studio > 3.4
3. Change the Target JVM version to 1.8
4. Click Apply

The reason is, Android studio is unable to add the below code in the module level Gradle file. Please add it manually.

kotlinOptions {
    jvmTarget = "1.8"
}

Just for the addon, search Target JVM version in the android studio search. It will take you directly to the option.

a picture is worth a thousand words

Feb 2020
android 3.4+
Go to File -> Settings -> Kotlin Compiler -> Target JVM Version > set to 1.8 and then make sure to do File -> Sync project with Gradle files

Or add this into build.gradle(module:app) in android block:

kotlinOptions {
           jvmTarget = "1.8"
         }

If you have many sourcesets/modules it can be cumbersome to configure the jvmTarget for each of them separately.

You can configure the jvmTarget for all of them at once like so:

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

This snippet can be used on top level of your gradle.build file

After modifying the gradle file Reimport All Gradle Imports. To check if it worked, open Project Structure and verify that IntelliJ correctly assigned JVM 1.8 to all Kotlin-Modules. It should look like this:

I would not recommend changing the platform directly in IntelliJ, because anyone else cloning your project for the first time is likely to face the same issue. Configuring it correctly in gradle has the advantage that IntelliJ is going to behave correctly for them right from the start.

As it is written in the using-maven docs from the Kotlin website:

You just have to put <kotlin.compiler.jvmTarget>1.8</kotlin.compiler.jvmTarget> into the properties section of your pom.xml

This helped my project to build, add this to module build.gradle file:

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

In my case, jvmTarget was already set in build.gradle file as below.

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

But my issue was still there. Finally, it gets resolved after Changing Target JVM version from 1.6 to 1.8 in Preferences > Other Settings > Kotlin Compiler > Target JVM version. see attached picture,

In my case, I solved this by following these two steps

1. Go to android studio preferences -> other settings -> kotlin compiler -> set Target JVM version = 1.8 
   if it doesn't work then go to the second option.

2. In your module-level build.gradle file add 
   compileOptions {
        sourceCompatibility = 1.8
        targetCompatibility = 1.8
    }
    tasks.withType(org.jetbrains.kotlin.gradle.tasks.KotlinCompile).all {
        kotlinOptions {
            jvmTarget = "1.8"
        }
    }

For me the reason was this configuration in my build gradle was in some modules and in some it wasnt

android {  
...      
kotlinOptions {
        val options = this as KotlinJvmOptions
        options.jvmTarget = "1.8"
    }
...
android {

For Gradle with Kotlin language (*.gradle.kts files), add this:

android {
    [...]
    kotlinOptions {
        this as KotlinJvmOptions
        jvmTarget = "1.8"
    }
}

Setting sourceCompatibility = JavaVersion.VERSION_1_8 enables desugaring, but it is currently unable to desugar all the Java 8 features that the Kotlin compiler uses.

Fix - Setting kotlinOptions.jvmTarget to JavaVersion.VERSION_1_8 in the app module Gradle would fix the issue.

Use Java 8 language features: https://developer.android.com/studio/write/java8-support

android {
  ...
  // Configure only for each module that uses Java 8
  // language features (either in its source code or
  // through dependencies).
  compileOptions {
    sourceCompatibility JavaVersion.VERSION_1_8
    targetCompatibility JavaVersion.VERSION_1_8
  }
  // For Kotlin projects
  kotlinOptions {
    jvmTarget = "1.8"
  }
}

in most cases this is enough:

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

if you have declared custom Gradle tasks like integrationTest for example, add a configuration for compile<YourTaskName>Kotlin as well:

compileIntegrationTestKotlin {
    kotlinOptions.jvmTarget = "1.8"
}

The next solution helped me. Add to build.gradle

 compileKotlin {
    kotlinOptions.jvmTarget = "1.8"
}

compileTestKotlin {
    kotlinOptions.jvmTarget = "1.8"
}

if you are in android project

in your app's build.gradle under android{}

android{
//other configs...
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    kotlinOptions {
        jvmTarget = "1.8"
    }
}

All answers here are using gradle but if someone like me ends up here and needs answer for maven:

    <build>
        <sourceDirectory>src/main/kotlin</sourceDirectory>
        <testSourceDirectory>src/test/kotlin</testSourceDirectory>

        <plugins>
            <plugin>
                <groupId>org.jetbrains.kotlin</groupId>
                <artifactId>kotlin-maven-plugin</artifactId>
                <version>${kotlin.version}</version>
                <executions>
                    <execution>
                        <id>compile</id>
                        <phase>compile</phase>
                        <goals>
                            <goal>compile</goal>
                        </goals>
                    </execution>
                    <execution>
                        <id>test-compile</id>
                        <phase>test-compile</phase>
                        <goals>
                            <goal>test-compile</goal>
                        </goals>
                    </execution>
                </executions>
                <configuration>
                    <jvmTarget>11</jvmTarget>
                </configuration>
            </plugin>
        </plugins>
    </build>

The change from jetbrains archetype for kotlin-jvm is the <configuration></configuration> specifying the jvmTarget. In my case 11

You may need to set both compileKotlin and compileTestKotlin. This works on gradle 6.5.1.

compileKotlin {
    kotlinOptions {
        languageVersion = "1.2"
        apiVersion = "1.2"
        jvmTarget = "1.8"
        javaParameters = true   // Useful for reflection.
    }
}

compileTestKotlin {
    kotlinOptions {
        languageVersion = "1.2"
        apiVersion = "1.2"
        jvmTarget = "1.8"
        javaParameters = true   // Useful for reflection.
    }
}

Nothing worked for me until I updated my kotlin plugin dependency.
Try this:
1. Invalidate cahce and restart.
2. Sync project (at least try to)
3. Go File -> Project Structure -> Suggestions
4. If there is an update regarding Kotlin, update it.
Hope it will help someone.

Using the Kotlin Gradle DSL, this solved the issue for me. I added this to the build.gradle.kts. This is in addition to the answer by Joel

val compileKotlin: KotlinCompile by tasks
compileKotlin.kotlinOptions.jvmTarget = JavaVersion.VERSION_1_8.toString()

If using Visual Studio Code** with Kotlin extension, go to the plugin management Crtl + Shift + x, type kotlin and click on manage (the little gear) >> Configure Extension Settings

on Kotlin >> Compiler >> Jvm:Target - type the java version. In my situation just typed 1.8

And then restart :-)

** vscode or just 'code' for linux

I'm using Kotlin and Gradle for normal JVM development, (not android) and this worked for me in build.gradle:

allprojects {
    tasks.withType(org.jetbrains.kotlin.gradle.tasks.KotlinCompile).configureEach {
        kotlinOptions.jvmTarget = JavaVersion.VERSION_11.toString()
    }
}

In my case File > Setting > Kotlin Compiler > Target JVM Version > 1.8

If you use Eclipse assuming you downloaded the Kotlin plugin:

Right click project -> Properties -> Kotlin Compiler -> Enable project specific settings -> JVM target version "1.8"

For recent versions of Android Studio, if changing just the Kotlin Target VM version didn't work.

File ? Project Structure ? Modules (app): set both "Source Compatibility" and "Target Compatibility" to "1.8 (Java 8)". Press "OK" and sync project with Gradle.

If you'r facing this message in a Spring Boot/Kotlin project, just set the property "kotlin.compiler.jvmTarget" to "1.8" in your pom.xml.

    <properties>
        <kotlin.version>1.3.70</kotlin.version>
        <kotlin.compiler.jvmTarget>1.8</kotlin.compiler.jvmTarget>
    </properties>
    ...

If non of the above answers don't work you can do this in kotlin dsl

android {
...

    tasks.withType<org.jetbrains.kotlin.gradle.tasks.KotlinCompile> {
        kotlinOptions {
            jvmTarget = "1.8"
        }
    }
}

Another hint for Eclipse users. After double checking the jvm target settings pointed out by other users, I still had the same problem, and that was caused by missing Kotlin Runtime Library. For eg, when creating a project with spring initializr, it is not added automatically. For adding it: right click on your project -> Build path -> Add libraries... -> User Library, and simply add org.jetbrains.kotlin.core.KOTLIN_CONTAINER

Make sure you refresh your gradle project afterwards (right click -> Gradle -> Refresh gradle project)