Shadow Guava时D8因minSdk版本报错的原因及解决方案

开发公共库时需要通过Shadow方式隔离依赖，避免使用者出现依赖冲突。直接引入Guava无问题，但Shadow后触发D8报错，提示MethodHandle.invoke和MethodHandle.invokeExact仅支持Android O（minSdk26及以上），但项目minSdk为16且无法升级。

主项目build.gradle.kts配置：

plugins {
    id("com.android.library")
}

android {
    namespace = "my.namespace"
    compileSdk = 34
    defaultConfig {
        minSdk = 16
    }
}

dependencies {
    implementation(project(path = ":Shadow-Module", configuration = "shadow"))
}

Shadow-Module的build.gradle.kts配置：

import com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar

plugins {
    id("java")
    id("com.github.johnrengelman.shadow") version "8.1.1"
}

val shadowJar = tasks.named<ShadowJar>("shadowJar") {
    isEnableRelocation = true
    relocationPrefix = "my.namespace.shadow"
}

dependencies {
    implementation("com.google.guava:guava:33.1.0-android")
}

报错信息：

AGPBI: {"kind":"error","text":"MethodHandle.invoke and MethodHandle.invokeExact are only supported starting with Android O (--min-api 26): Lmy/namespace/shadow/com/google/common/hash/Hashing$Crc32cMethodHandles;newCrc32c()Ljava/util/zip/Checksum;","sources":[{"file":"~/.gradle/caches/transforms-4/ddfd1a8942a2e6d1a88e6eb87139afdd/transformed/jetified-Shadow-Module-all.jar"}],"tool":"D8"}

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':My-SDK:mergeDexAppDebugAndroidTest'.
> Could not resolve all files for configuration ':My-SDK:appDebugAndroidTestRuntimeClasspath'.
   > Failed to transform Shadow-Modules-all.jar (project :Shadow-Modules) to match attributes {artifactType=android-dex, dexing-component-attributes=ComponentSpecificParameters(minSdkVersion=16, debuggable=true, enableCoreLibraryDesugaring=false, enableGlobalSynthetics=false, enableApiModeling=false, dependenciesClassesAreInstrumented=false, asmTransformComponent=null, useJacocoTransformInstrumentation=false, enableDesugaring=true, needsClasspath=true, useFullClasspath=false, componentIfUsingFullClasspath=null), org.gradle.libraryelements=jar, org.gradle.usage=java-runtime}.
      > Execution failed for DexingWithClasspathTransform: ~/.gradle/caches/transforms-4/ddfd1a8942a2e6d1a88e6eb87139afdd/transformed/jetified-Shadow-Module-all.jar.
         > Error while dexing.
           Increase the minSdkVersion to 26 or above.

1. 直接引入Guava的适配逻辑：Guava的Android专属版本（guava:xx.x.x-android）内置了低版本适配机制，AGP在处理直接依赖时，会根据项目minSdk自动筛选兼容的实现类，跳过MethodHandle这类仅支持高API的代码。
2. Shadow插件的处理缺陷：Shadow插件基于Java插件构建，仅负责重新打包并 relocate 类路径，不会识别Android的minSdk适配规则。这导致Guava中原本仅为高版本Android准备的MethodHandle相关实现类被一并打包进Shadow jar，D8处理时检测到高API调用，触发报错。

方式一：在Shadow模块启用Core Library Desugaring #

Core Library Desugaring可让低版本Android支持Java 8+的API，包括MethodHandle。需将Shadow模块从Java插件切换为Android Library插件，启用Desugaring：

修改Shadow-Module的build.gradle.kts：

plugins {
    id("com.android.library")
    id("com.github.johnrengelman.shadow") version "8.1.1"
}

android {
    namespace = "my.namespace.shadow"
    compileSdk = 34
    defaultConfig {
        minSdk = 16
    }
    compileOptions {
        sourceCompatibility = JavaVersion.VERSION_1_8
        targetCompatibility = JavaVersion.VERSION_1_8
        coreLibraryDesugaringEnabled = true
    }
}

val shadowJar = tasks.named<ShadowJar>("shadowJar") {
    isEnableRelocation = true
    relocationPrefix = "my.namespace.shadow"
}

dependencies {
    implementation("com.google.guava:guava:33.1.0-android")
    coreLibraryDesugaring("com.android.tools:desugar_jdk_libs:2.0.4")
}

方式二：排除Guava中含MethodHandle的类 #

通过Shadow插件配置，直接排除包含高API调用的类，仅保留低版本兼容实现：

修改Shadow-Module的shadowJar任务配置：

val shadowJar = tasks.named<ShadowJar>("shadowJar") {
    isEnableRelocation = true
    relocationPrefix = "my.namespace.shadow"
    // 排除使用MethodHandle的Crc32c实现类
    exclude("com/google/common/hash/Hashing\$Crc32cMethodHandles.class")
    // 若有其他报错，可补充排除对应类
}

注意：此方法仅适用于业务未用到被排除类的场景，若需使用相关功能，优先选择方式一。

内容的提问来源于stack exchange，提问作者Hounshell