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

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 can fix this issue as follows:

Open the IntelliJ preferences

Go to Build, Execution, Deployment > Compiler > Kotlin Compiler BUT Other Settings > Kotlin compiler if Android Studio > 3.4

Change the Target JVM version to 1.8

Click Apply

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

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 didn't work until I moved 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.

Open the IntelliJ preferences Go to Build, Execution, Deployment > Compiler > Kotlin Compiler BUT Other Settings > Kotlin compiler if Android Studio > 3.4 Change the Target JVM version to 1.8 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"
}

https://i.stack.imgur.com/VmxAo.png

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:

https://i.stack.imgur.com/SdndZ.png

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

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,

https://i.stack.imgur.com/zonA2.png

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"
        }
    }

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 {

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

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

The next solution helped me. Add to build.gradle

 compileKotlin {
    kotlinOptions.jvmTarget = "1.8"
}

compileTestKotlin {
    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"
}

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

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.

https://i.stack.imgur.com/k77tB.png

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"
  }
}

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.
    }
}

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"
    }
}

If non of the above answers works, you can do this in kotlin dsl

android {
...

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

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()
    }
}

I did all steps but didn't success the problem was

implementation 'org.jetbrains.kotlin:kotlin-stdlib:1.4.32'

when I updated to

implementation 'org.jetbrains.kotlin:kotlin-stdlib:1.5.30'

shows that problem when I back to

implementation 'org.jetbrains.kotlin:kotlin-stdlib:1.4.32'

the problem fixed

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

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 you use Eclipse assuming you downloaded the Kotlin plugin:

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

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