How to create new module (android library) into libgdx apllication? (if it is possible)

Question

I created libgdx application with android module (kotlin - libktx) - I use: https://github.com/tommyettinger/gdx-liftoff

I tried to add new module (Android Library) in Android Studio, but it do not work: Cannot add extension with name 'kotlin', as there is an extension already registered with that name.

I tried to modify build.gradle of created module, but it do not help. Just the error was changing. I would like to ask if you know: is it possible to add Android Library Module to libgdx application? And how?

If I add new module (Java or Kotlin Library), it works. But I would like to create module with android dependencies. If it is possible. Thank you.

UPDATE:

Here are my gradle files and description of changes what I tried to do. If anyone can help.

I am trying to do this with the fresh libgdx project. I made a copy of folder "android" and rename it to "androTest".

I changed in project (in root folder): settings.gradle

include 'core', 'lwjgl3', 'android', 'androTest'

In root folder in file build.gradle I made a copy of part with subproject configuration of android and the final file is:

buildscript {
    repositories {
        mavenCentral()
        maven { url 'https://s01.oss.sonatype.org' }
        mavenLocal()
        google()
        gradlePluginPortal()
        maven { url 'https://oss.sonatype.org/content/repositories/snapshots/' }
        maven { url 'https://s01.oss.sonatype.org/content/repositories/snapshots/' }
    }
    dependencies {
        classpath "com.android.tools.build:gradle:$androidPluginVersion"
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlinVersion"

        // This follows advice from https://blog.gradle.org/log4j-vulnerability
        constraints {
            classpath("org.apache.logging.log4j:log4j-core") {
                version {
                    strictly("[2.18, 3[")
                    prefer("2.18.0")
                }
                because("CVE-2021-44228, CVE-2021-45046, CVE-2021-45105: Log4j vulnerable to remote code execution and other critical security vulnerabilities")
            }
        }
    }
}

allprojects {
    apply plugin: 'eclipse'
    apply plugin: 'idea'
}

configure(subprojects - project(':android')) {
    apply plugin: 'java-library'
    apply plugin: 'kotlin'
    sourceCompatibility = 1.8
    compileJava {
        options.incremental = true
    }
    dependencies {
        // This follows advice from https://blog.gradle.org/log4j-vulnerability
        constraints {
            implementation("org.apache.logging.log4j:log4j-core") {
                version {
                    strictly("[2.18, 3[")
                    prefer("2.18.0")
                }
                because("CVE-2021-44228, CVE-2021-45046, CVE-2021-45105: Log4j vulnerable to remote code execution and other critical security vulnerabilities")
            }
        }
    }
}

configure(subprojects - project(':androTest')) {
    apply plugin: 'java-library'
    apply plugin: 'kotlin'
    sourceCompatibility = 1.8
    compileJava {
        options.incremental = true
    }
    dependencies {
        // This follows advice from https://blog.gradle.org/log4j-vulnerability
        constraints {
            implementation("org.apache.logging.log4j:log4j-core") {
                version {
                    strictly("[2.18, 3[")
                    prefer("2.18.0")
                }
                because("CVE-2021-44228, CVE-2021-45046, CVE-2021-45105: Log4j vulnerable to remote code execution and other critical security vulnerabilities")
            }
        }
    }
}

subprojects {
    version = '1.0.0'
    ext.appName = 'TestLibGDXProject'
    repositories {
        mavenCentral()
        maven { url 'https://s01.oss.sonatype.org' }
        mavenLocal()
        gradlePluginPortal()
        maven { url 'https://oss.sonatype.org/content/repositories/snapshots/' }
        maven { url 'https://s01.oss.sonatype.org/content/repositories/snapshots/' }
        maven { url 'https://jitpack.io' }
    }
}

eclipse.project.name = 'TestLibGDXProject' + '-parent'

File build.gradle from new folder "androTest" is the same as build.gradle in original "android" folder except of last line. In "androTest" I changed only last line. There is file from "androTest" folder:

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

android {
    compileSdkVersion 30
    sourceSets {
        main {
            manifest.srcFile 'AndroidManifest.xml'
            java.srcDirs = ['src/main/java', 'src/main/kotlin']
            aidl.srcDirs = ['src/main/java', 'src/main/kotlin']
            renderscript.srcDirs = ['src/main/java', 'src/main/kotlin']
            res.srcDirs = ['res']
            assets.srcDirs = ['../assets']
            jniLibs.srcDirs = ['libs']
        }
    }
    packagingOptions {
        // Preventing from license violations (more or less):
        pickFirst 'META-INF/LICENSE.txt'
        pickFirst 'META-INF/LICENSE'
        pickFirst 'META-INF/license.txt'
        pickFirst 'META-INF/LGPL2.1'
        pickFirst 'META-INF/NOTICE.txt'
        pickFirst 'META-INF/NOTICE'
        pickFirst 'META-INF/notice.txt'
        // Excluding unnecessary meta-data:
        exclude 'META-INF/robovm/ios/robovm.xml'
        exclude 'META-INF/DEPENDENCIES.txt'
        exclude 'META-INF/DEPENDENCIES'
        exclude 'META-INF/dependencies.txt'
    }
    defaultConfig {
        applicationId 'com.testgdx.testlibgdxproject'
        minSdkVersion 19
        targetSdkVersion 30
        versionCode 1
        versionName "1.0"
        multiDexEnabled true
    }
    compileOptions {
        sourceCompatibility "1.8"
        targetCompatibility "1.8"
        coreLibraryDesugaringEnabled true
    }
    kotlinOptions.jvmTarget = "1.8"
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }

}

repositories {
    // needed for AAPT2, may be needed for other tools
    google()
}

configurations { natives }

dependencies {
    coreLibraryDesugaring 'com.android.tools:desugar_jdk_libs:1.1.5'
    implementation "com.badlogicgames.gdx:gdx-backend-android:$gdxVersion"
    implementation project(':core')

    natives "com.badlogicgames.gdx:gdx-platform:$gdxVersion:natives-arm64-v8a"
    natives "com.badlogicgames.gdx:gdx-platform:$gdxVersion:natives-armeabi-v7a"
    natives "com.badlogicgames.gdx:gdx-platform:$gdxVersion:natives-x86"
    natives "com.badlogicgames.gdx:gdx-platform:$gdxVersion:natives-x86_64"

    // This follows advice from https://blog.gradle.org/log4j-vulnerability
    constraints {
        implementation("org.apache.logging.log4j:log4j-core") {
            version {
                strictly("[2.18, 3[")
                prefer("2.18.0")
            }
            because("CVE-2021-44228, CVE-2021-45046, CVE-2021-45105: Log4j vulnerable to remote code execution and other critical security vulnerabilities")
        }
    }
}

// Called every time gradle gets executed, takes the native dependencies of
// the natives configuration, and extracts them to the proper libs/ folders
// so they get packed with the APK.
task copyAndroidNatives() {
    doFirst {
        file("libs/armeabi-v7a/").mkdirs()
        file("libs/arm64-v8a/").mkdirs()
        file("libs/x86_64/").mkdirs()
        file("libs/x86/").mkdirs()

        configurations.getByName("natives").copy().files.each { jar ->
            def outputDir = null
            if(jar.name.endsWith("natives-armeabi-v7a.jar")) outputDir = file("libs/armeabi-v7a")
            if(jar.name.endsWith("natives-arm64-v8a.jar")) outputDir = file("libs/arm64-v8a")
            if(jar.name.endsWith("natives-x86_64.jar")) outputDir = file("libs/x86_64")
            if(jar.name.endsWith("natives-x86.jar")) outputDir = file("libs/x86")
            if(outputDir != null) {
                copy {
                    from zipTree(jar)
                    into outputDir
                    include "*.so"
                }
            }
        }
    }
}
tasks.matching { it.name.contains("merge") && it.name.contains("JniLibFolders") }.configureEach { packageTask ->
    packageTask.dependsOn 'copyAndroidNatives'
}

task run(type: Exec) {
    def path
    def localProperties = project.file("../local.properties")
    if (localProperties.exists()) {
        Properties properties = new Properties()
        localProperties.withInputStream { instr ->
            properties.load(instr)
        }
        def sdkDir = properties.getProperty('sdk.dir')
        if (sdkDir) {
            path = sdkDir
        } else {
            path = "$System.env.ANDROID_SDK_ROOT"
        }
    } else {
        path = "$System.env.ANDROID_SDK_ROOT"
    }

    def adb = path + "/platform-tools/adb"
    commandLine "$adb", 'shell', 'am', 'start', '-n', 'com.testgdx.testlibgdxproject/com.testgdx.testlibgdxproject.android.AndroidLauncher'
}

eclipse.project.name = appName + "-androTest"

If I try to build it I can see error:

A problem occurred evaluating project ':android'.
> Failed to apply plugin 'kotlin-android'.
   > Cannot add extension with name 'kotlin', as there is an extension already registered with that name.

if I remove the problem line from build.gradle file (apply plugin: 'kotlin-android') I can see new error:

* What went wrong:
A problem occurred evaluating project ':android'.
> Could not get unknown property 'kotlinOptions' for extension 'android' of type com.android.build.gradle.internal.dsl.BaseAppModuleExtension.

I remove the line from build.gradle file (kotlinOptions.jvmTarget = "1.8") and I can see error:

A problem occurred configuring project ':android'.
> com.android.build.gradle.internal.BadPluginException: The 'java' plugin has been applied, but it is not compatible with the Android plugins.

All errors are from original "android" module.

Answer 1

Liftoff's partial author here. It looks like the issue has to do with configure(subprojects - project(':android')) { in the root build.gradle file, which includes all projects except for the android project, and still includes the newly-added androTest project. You probably want configure(subprojects - project(':android') - project(':androTest')) { instead, which makes androTest use the same configuration (or lack of it) that the android project uses. You'll also want to remove the entire configure(subprojects - project(':androTest')) { block, which is entirely broken because it will try to configure android with the same config the last block excluded android from.

I haven't pushed a release in a little while, but one should be coming up soon. I noticed how ugly the dependency constraints are here, and they aren't needed in the current Gradle version, so the next GDX-Liftoff release will remove the constraints (and you can remove them now yourself if you want).

I hope this helps.