解决Flutter项目报错：Could not create an instance of LibraryVariantBuilderImpl

问题背景 #

格式化电脑并重装Android Studio及相关依赖后，原本可正常运行的Flutter项目启动报错，错误指向:wakelock模块未指定namespace，尽管android/app/build.gradle中已正确配置namespace。

报错信息 #

FAILURE: Build failed with an exception.

* What went wrong:
A problem occurred configuring project ':wakelock'.
> Could not create an instance of type com.android.build.api.variant.impl.LibraryVariantBuilderImpl.
   > Namespace not specified. Please specify a namespace in the module's build.gradle file like so:

     android {
         namespace 'com.example.namespace'
     }

     If the package attribute is specified in the source AndroidManifest.xml, it can be migrated automatically to the namespace value in the build.gradle file using the AGP Upgrade Assistant; please refer to https://developer.android.com/studio/build/agp-upgrade-assistant for more information.

当前配置文件 #

android/app/build.gradle #

plugins {
    id "com.android.application"
    id "kotlin-android"
    id "dev.flutter.flutter-gradle-plugin"
}
def localProperties = new Properties()
def localPropertiesFile = rootProject.file('local.properties')
if (localPropertiesFile.exists()) {
    localPropertiesFile.withReader('UTF-8') { reader ->
        localProperties.load(reader)
    }
}

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

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


android {
    namespace "com.generalomosco.myapp"
    compileSdkVersion flutter.compileSdkVersion
    ndkVersion flutter.ndkVersion

    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }

    kotlinOptions {
        jvmTarget = '1.8'
    }

    sourceSets {
        main.java.srcDirs += 'src/main/kotlin'
    }

    defaultConfig {
        applicationId "com.generalomosco.myapp"
        minSdkVersion 24
        targetSdkVersion flutter.targetSdkVersion
        versionCode flutterVersionCode.toInteger()
        versionName flutterVersionName
    }

    buildTypes {
        release {
            signingConfig signingConfigs.debug
        }
    }
}

flutter {
    source '../..'
}

dependencies {
    /*implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"*/
}

settings.gradle #

pluginManagement {
    def flutterSdkPath = {
        def properties = new Properties()
        file("local.properties").withInputStream { properties.load(it) }
        def flutterSdkPath = properties.getProperty("flutter.sdk")
        assert flutterSdkPath != null, "flutter.sdk not set in local.properties"
        return flutterSdkPath
    }()

    includeBuild("$flutterSdkPath/packages/flutter_tools/gradle")

    repositories {
        google()
        mavenCentral()
        gradlePluginPortal()
    }
}

plugins {
    id "dev.flutter.flutter-plugin-loader" version "1.0.0"
    id "com.android.application" version "8.0.2" apply false
    id "org.jetbrains.kotlin.android" version "1.7.10" apply false
}

include ":app"

解决方案 #

方案1：升级wakelock依赖到适配AGP 8.0+的版本 #

打开项目根目录的pubspec.yaml，将wakelock的版本更新为最新稳定版，执行flutter pub get拉取新依赖。新版本的wakelock已适配Android Gradle Plugin（AGP）8.0+的namespace要求。

方案2：通过Gradle脚本为:wakelock模块补全namespace #

在项目根目录的build.gradle中添加以下代码，自动为未配置namespace的库模块添加默认namespace：

subprojects {
    afterEvaluate { project ->
        if (project.plugins.hasPlugin('com.android.library') && project.android.namespace == null) {
            if (project.name == "wakelock") {
                project.android {
                    namespace "dev.fluttercommunity.wakelock"
                }
            } else {
                project.android {
                    namespace "com.example.${project.name}"
                }
            }
        }
    }
}

方案3：降级Android Gradle Plugin版本（临时方案） #

修改settings.gradle中的AGP版本为7.x系列（如7.4.2），同时调整Kotlin版本以匹配：

plugins {
    id "dev.flutter.flutter-plugin-loader" version "1.0.0"
    id "com.android.application" version "7.4.2" apply false
    id "org.jetbrains.kotlin.android" version "1.8.20" apply false
}

此方案仅作为临时 workaround，长期建议使用方案1或2以适配最新工具链。

内容的提问来源于stack exchange，提问作者General Omosco