如何在LibGDX项目中添加Android Library模块？解决Gradle报错

问题背景 #

用gdx-liftoff创建带Android模块（Kotlin-libktx）的LibGDX应用，尝试添加Android Library模块时触发报错：Cannot add extension with name 'kotlin', as there is an extension already registered with that name。修改build.gradle后报错类型变化，但核心问题未解决。需创建带Android依赖的模块，Java/Kotlin Library模块可正常工作，但Android Library模块无法构建。

错误根源 #

根build.gradle中重复且错误的插件配置导致冲突：

• 两次使用configure(subprojects - project(':xxx'))，使得所有子项目（包括Android模块）被强制应用java-library和kotlin插件
• Android插件本身已集成Kotlin支持，重复应用kotlin插件会引发扩展名冲突
• java-library插件与Android插件不兼容，触发后续构建错误

分步解决方案 #

1. 修复根build.gradle的插件配置 #

将根目录下的build.gradle中重复的configure块替换为仅针对非Android模块的统一配置，避免Android模块被错误应用Java/Kotlin插件：

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"

        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'
}

// 仅对非Android子项目应用Java/Kotlin插件
configure(subprojects.findAll { !it.name.startsWith('android') }) {
    apply plugin: 'java-library'
    apply plugin: 'kotlin'
    sourceCompatibility = 1.8
    compileJava {
        options.incremental = true
    }
    dependencies {
        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'

2. 调整新Android Library模块（androTest）的build.gradle #

将模块类型从Application改为Library，并适配相关配置：

// 替换原Application插件为Library插件
apply plugin: 'com.android.library'
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 {
        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'
        exclude 'META-INF/robovm/ios/robovm.xml'
        exclude 'META-INF/DEPENDENCIES.txt'
        exclude 'META-INF/DEPENDENCIES'
        exclude 'META-INF/dependencies.txt'
    }
    defaultConfig {
        // Android Library不需要applicationId，删除该行
        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 {
    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"

    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")
        }
    }
}

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'
}

// Android Library不需要run任务，删除或注释该行以下的run任务代码
// task run(type: Exec) {
//     ... 原run任务代码 ...
// }

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

3. 保留原Android模块配置 #

原Android模块的build.gradle无需修改，确保其插件为com.android.application和kotlin-android即可。

4. 同步并验证构建 #

• 点击Android Studio的Sync Project with Gradle Files按钮同步配置
• 执行./gradlew clean build命令验证构建是否成功

内容的提问来源于stack exchange，提问作者fram4