[SOLVED] Ionic Capacitor - Unknown Kotlin JVM target: 21

Ionic Capacitor - Unknown Kotlin JVM target: 21

My Ionic Capacitor Android won't run. I am getting "Unknown Kotlin JVM target: 21" error.
My exact error is:

Could not determine the dependencies of task ':capacitor-inappbrowser:compileDebugKotlin'.

Unknown Kotlin JVM target: 21

I ran the "java -version" and "gradle -v" commands from Visual Studio Code terminal.

$ java -version
java version "21.0.4" 2024-07-16 LTS
Java(TM) SE Runtime Environment (build 21.0.4+8-LTS-274)
Java HotSpot(TM) 64-Bit Server VM (build 21.0.4+8-LTS-274, mixed mode, sharing)

$ gradle -v

------------------------------------------------------------
Gradle 8.9
------------------------------------------------------------

Build time:    2024-07-11 14:37:41 UTC
Revision:      d536ef36a19186ccc596d8817123e5445f30fef8

Kotlin:        1.9.23
Groovy:        3.0.21
Ant:           Apache Ant(TM) version 1.10.13 compiled on January 4 2023
Launcher JVM:  21.0.4 (Oracle Corporation 21.0.4+8-LTS-274)
Daemon JVM:    C:\Program Files\Java\jdk-21 (no JDK specified, using current Java home)
OS:            Windows 11 10.0 amd64

Here is the capacitor.build.gradle file in the Android project...

// DO NOT EDIT THIS FILE! IT IS GENERATED EACH TIME "capacitor update" IS RUN

android {
  compileOptions {
      sourceCompatibility JavaVersion.VERSION_17
      targetCompatibility JavaVersion.VERSION_17
  }
}

apply from: "../capacitor-cordova-android-plugins/cordova.variables.gradle"
dependencies {
    implementation project(':capacitor-community-fcm')
    implementation project(':capacitor-community-file-opener')
    implementation project(':capacitor-community-sqlite')
    implementation project(':capacitor-mlkit-barcode-scanning')
    implementation project(':capacitor-app')
    implementation project(':capacitor-app-launcher')
    implementation project(':capacitor-browser')
    implementation project(':capacitor-camera')
    implementation project(':capacitor-device')
    implementation project(':capacitor-filesystem')
    implementation project(':capacitor-geolocation')
    implementation project(':capacitor-haptics')
    implementation project(':capacitor-inappbrowser')
    implementation project(':capacitor-keyboard')
    implementation project(':capacitor-network')
    implementation project(':capacitor-preferences')
    implementation project(':capacitor-push-notifications')
    implementation project(':capacitor-splash-screen')
    implementation project(':capacitor-status-bar')
    implementation project(':capacitor-toast')
    implementation project(':capacitor-barcode-scanner')

}


if (hasProperty('postBuildExtras')) {
  postBuildExtras()
}

Build.gradle file....

// Top-level build file where you can add configuration options common to all sub-projects/modules.

buildscript {

    repositories {
        google()
        mavenCentral()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:8.7.1'
        classpath 'com.google.gms:google-services:4.4.0'

        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

apply from: "variables.gradle"

allprojects {
    repositories {
        google()
        mavenCentral()
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

gradle-wrapper.properties file...

#Fri Dec 06 09:02:05 CST 2024
distributionBase=GRADLE_USER_HOME
distributionPath=wrapper/dists
distributionUrl=https\://services.gradle.org/distributions/gradle-8.9-bin.zip
networkTimeout=10000
zipStoreBase=GRADLE_USER_HOME
zipStorePath=wrapper/dists

Solution

Android Gradle plugin is not the same as gradle. Use [https://docs.gradle.org/current/userguide/compatibility.html][1]. Be sure that gradle versions and Java versions match up. Update your Path and JAVA_HOME in System Environmental Variables and then restart your computer.