升级Gradle 8后minifyReleaseWithR8出现BuildConfig类重复定义问题

报错信息 #

Type com.my.package.BuildConfig is defined multiple times: C:\Users\MyProject\build\firebase_messaging\intermediates\runtime_library_classes_jar\release\classes.jar:com/my/package/BuildConfig.class, C:\Users\MyProject\firebase_core\intermediates\runtime_library_classes_jar\release\classes.jar:com/my/package/BuildConfig.class

项目配置 #

根目录build.gradle #

buildscript {
    ext.kotlin_version = '1.8.22'
    repositories {
        google()
        mavenCentral()
        maven {
            url "https://plugins.gradle.org/m2/"
        }
    }

    dependencies {
        classpath 'com.android.tools.build:gradle:8.1.4'
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
        classpath 'com.google.gms:google-services:4.4.0'
        classpath "com.jeff-media:fix-javadoc-plugin:1.19"
    }
}

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

subprojects{
    afterEvaluate {
        android {
            namespace 'com.my.package'
        }
    }
}

rootProject.buildDir = '../build'
subprojects {
    project.buildDir = "${rootProject.buildDir}/${project.name}"
    project.evaluationDependsOn(':app')
}

tasks.register("clean", Delete) {
    delete rootProject.buildDir
}
apply plugin: "com.jeff-media.fix-javadoc-plugin"

App模块build.gradle #

def localProperties = new Properties()
def localPropertiesFile = rootProject.file('local.properties')
if (localPropertiesFile.exists()) {
    localPropertiesFile.withReader('UTF-8') { reader ->
        localProperties.load(reader)
    }
}

def flutterRoot = localProperties.getProperty('flutter.sdk')
if (flutterRoot == null) {
    throw new GradleException("Flutter SDK not found. Define location with flutter.sdk in the local.properties file.")
}

def flutterVersionCode = localProperties.getProperty('flutter.versionCode')
if (flutterVersionCode == null) {
    flutterVersionCode = '1'
}

def flutterVersionName = localProperties.getProperty('flutter.versionName')
if (flutterVersionName == null) {
    flutterVersionName = '1.0'
}

apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"

def keystoreProperties = new Properties()
def keystorePropertiesFile = rootProject.file('key.properties')
if (keystorePropertiesFile.exists()) {
    keystoreProperties.load(new FileInputStream(keystorePropertiesFile))
}

android {
    compileSdk 33
    sourceSets {
        main.java.srcDirs = ['src/main/kotlin', 'build/generated/source/buildConfig/release', 'build/generated/source/buildConfig/debug']
    }

    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }

    kotlinOptions {
        jvmTarget = '1.8'
    }
    defaultConfig {
        applicationId 'com.my.package'
        minSdkVersion 23
        targetSdkVersion 33
        versionCode flutterVersionCode.toInteger()
        versionName flutterVersionName
        multiDexEnabled true
    }
    signingConfigs {
        release {
            keyAlias keystoreProperties['keyAlias']
            keyPassword keystoreProperties['keyPassword']
            storeFile keystoreProperties['storeFile'] ? file(keystoreProperties['storeFile']) : null
            storePassword keystoreProperties['storePassword']
        }
    }

    buildTypes {

        release {
            signingConfig signingConfigs.release

            minifyEnabled true
            shrinkResources true

            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'

            ndk {
                abiFilters 'armeabi-v7a', 'arm64-v8a', 'x86', 'x86_64'
            }

        }

    }
    lint {
        disable 'InvalidPackage'
    }
    namespace 'com.my.package'
}

flutter {
    source '../..'
}

dependencies {
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
    implementation 'com.google.firebase:firebase-messaging:23.3.1'
    implementation 'androidx.multidex:multidex:2.0.1'
}

apply plugin: 'com.google.gms.google-services'

Flutter环境信息 #

[√] Flutter (Channel stable, 3.16.0, on Microsoft Windows [Version 10.0.22621.2715], locale en-US)
    • Flutter version 3.16.0 on channel stable at C:\Development\flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision db7ef5bf9f (9 days ago), 2023-11-15 11:25:44 -0800
    • Engine revision 74d16627b9
    • Dart version 3.2.0
    • DevTools version 2.28.2

[√] Windows Version (Installed version of Windows is version 10 or higher)

[√] Android toolchain - develop for Android devices (Android SDK version 34.0.0)
    • Android SDK at C:\Users\MSM\AppData\Local\Android\sdk
    • Platform android-34, build-tools 34.0.0
    • Java binary at: C:\Program Files\Android\Android Studio\jbr\bin\java
    • Java version OpenJDK Runtime Environment (build 17.0.6+0-b2043.56-10027231)
    • All Android licenses accepted.

[√] Chrome - develop for the web
[√] VS Code (version 1.79.2)
    • VS Code at C:\Users\MSM\AppData\Local\Programs\Microsoft VS Code
    • Flutter extension version 3.76.0

[√] Connected device (3 available)
    • Windows (desktop) • windows • windows-x64    • Microsoft Windows [Version 10.0.22621.2715]
    • Chrome (web)      • chrome  • web-javascript • Google Chrome 119.0.6045.124
    • Edge (web)        • edge    • web-javascript • Microsoft Edge 119.0.2151.72

[√] Network resources
    • All expected network resources are available.

• No issues found!

已尝试的无效方案 #

• 降级至Gradle7，但出现更多问题，不得不回退到Gradle8
• 清理/重新构建项目
• 无效缓存并重启
• 删除项目及根目录下的.build、.gradle文件夹

解决方案 #

问题根源在于根目录build.gradle中给所有子模块强制设置了相同的namespace 'com.my.package'，包括firebase_messaging、firebase_core这些第三方依赖模块，导致它们生成了与主App模块相同包名的BuildConfig类，在R8混淆时冲突。

修改根目录的subprojects配置，只给你的App模块设置namespace，排除第三方子模块：

subprojects{
    afterEvaluate {
        // 只给app模块设置namespace，跳过firebase等第三方子模块
        if (project.name == 'app') {
            android {
                namespace 'com.my.package'
            }
        }
    }
}

或者更灵活地排除所有非自定义的子模块：

subprojects{
    afterEvaluate {
        // 仅当项目是本地模块而非第三方依赖时设置namespace
        if (file("src/main").exists()) {
            android {
                namespace 'com.my.package'
            }
        }
    }
}

修改后，执行clean再重新构建项目即可解决BuildConfig重复定义的问题。

内容的提问来源于stack exchange，提问作者Gombo Khorloo