添加Firebase BoM至顶级build.gradle报错：找不到implementation()方法

修改项目顶级build.gradle添加Firebase BoM后，抛出错误：

Could not find method implementation() for arguments [DefaultExternalModuleDependency{group='com.google.firebase', name='firebase-bom', version='31.3.0', configuration='default'}] on object of type org.gradle.api.internal.artifacts.dsl.dependencies.DefaultDependencyHandler.

相关配置文件 #

修改前的顶级build.gradle #

// Top-level build file where you can add configuration options common to all sub-projects/modules.
plugins {
    id 'com.android.application' version '7.4.2' apply false
    id 'com.android.library' version '7.4.2' apply false
}

修改后的顶级build.gradle #

// Top-level build file where you can add configuration options common to all sub-projects/modules.
plugins {
    id 'com.android.application' version '7.4.2' apply false
    id 'com.android.library' version '7.4.2' apply false
}
dependencies {
    // Import the Firebase BoM
    implementation platform('com.google.firebase:firebase-bom:31.3.0')

    // TODO: Add the dependencies for Firebase products you want to use
    // When using the BoM, don't specify versions in Firebase dependencies
}

app模块的build.gradle #

plugins {
    id 'com.android.application'
}

android {
    namespace 'com.example.delivery1'
    compileSdk 33

    defaultConfig {
        applicationId "com.example.delivery1"
        minSdk 25
        targetSdk 33
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    buildFeatures {
        viewBinding true
    }
}

dependencies {
    implementation 'androidx.appcompat:appcompat:1.6.1'
    implementation 'com.google.android.material:material:1.8.0'
    implementation 'androidx.constraintlayout:constraintlayout:2.1.4'
    implementation 'androidx.lifecycle:lifecycle-livedata-ktx:2.6.1'
    implementation 'androidx.lifecycle:lifecycle-viewmodel-ktx:2.6.1'
    implementation 'androidx.navigation:navigation-fragment:2.5.3'
    implementation 'androidx.navigation:navigation-ui:2.5.3'
    testImplementation 'junit:junit:4.13.2'
    androidTestImplementation 'androidx.test.ext:junit:1.1.5'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.5.1'
    implementation(platform("org.jetbrains.kotlin:kotlin-bom:1.8.0"))
    classpath 'com.google.gms:google-services:4.3.15'
}

1. 修正顶级build.gradle #

顶级配置文件仅负责声明全局插件，不能使用implementation关键字，需将google-services插件添加到plugins块中：

// Top-level build file where you can add configuration options common to all sub-projects/modules.
plugins {
    id 'com.android.application' version '7.4.2' apply false
    id 'com.android.library' version '7.4.2' apply false
    // 添加google-services插件，apply false表示不在全局应用，仅让子模块可引用
    id 'com.google.gms.google-services' version '4.3.15' apply false
}

2. 调整app模块的build.gradle #

• 将Firebase BoM的配置移到app模块的dependencies块中，因为implementation是模块级依赖的专属关键字
• 在app模块的plugins块中添加google-services插件
• 删除app模块dependencies里错误的classpath 'com.google.gms:google-services:4.3.15'，classpath仅能在顶级配置中声明插件依赖

修改后的app模块代码：

plugins {
    id 'com.android.application'
    // 应用google-services插件
    id 'com.google.gms.google-services'
}

android {
    namespace 'com.example.delivery1'
    compileSdk 33

    defaultConfig {
        applicationId "com.example.delivery1"
        minSdk 25
        targetSdk 33
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    buildFeatures {
        viewBinding true
    }
}

dependencies {
    implementation 'androidx.appcompat:appcompat:1.6.1'
    implementation 'com.google.android.material:material:1.8.0'
    implementation 'androidx.constraintlayout:constraintlayout:2.1.4'
    implementation 'androidx.lifecycle:lifecycle-livedata-ktx:2.6.1'
    implementation 'androidx.lifecycle:lifecycle-viewmodel-ktx:2.6.1'
    implementation 'androidx.navigation:navigation-fragment:2.5.3'
    implementation 'androidx.navigation:navigation-ui:2.5.3'
    testImplementation 'junit:junit:4.13.2'
    androidTestImplementation 'androidx.test.ext:junit:1.1.5'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.5.1'
    implementation(platform("org.jetbrains.kotlin:kotlin-bom:1.8.0"))
    
    // 在此添加Firebase BoM
    implementation platform('com.google.firebase:firebase-bom:31.3.0')
}

错误原因 #

• 顶级build.gradle属于项目级配置，没有Android插件提供的implementation方法，该关键字仅能在具体模块（如app）的dependencies块中使用
• app模块的dependencies块不支持classpath，这个语法仅用于在顶级配置中声明插件依赖

内容的提问来源于stack exchange，提问作者Baalback