Api to Implementation - 由于版本不同，无法再编译firebase项目

Question

我有一个主应用程序和一个包装所有firebase相关代码的模块。

我遇到的问题是，只要我将firebase依赖项从api更改为implementation，我就无法再编译项目了。我的主项目构建失败，出现以下错误：

错误

Error:FAILURE: Build failed with an exception.
* What went wrong:
Execution failed for task ':app:preDevDeDebugBuild'.
> Android dependency 'com.google.firebase:firebase-core' has different version for the compile (9.0.0) and runtime (11.8.0) classpath. You should manually set the same version via DependencyResolution

我的主应用程序如下所示：

dependencies {

    implementation project(':module-firestore')

    // NO OTHER FIRESTORE IMPORTS; NOT HERE NOT IN ANY OTHER MODULE!
}

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

我的firebase模块如下所示：

dependencies {

    // ----------------------
    // Firebase
    // ----------------------

    api "com.google.firebase:firebase-core:${versions.playServices}"
    api "com.google.firebase:firebase-auth:${versions.playServices}"
    api "com.google.firebase:firebase-ads:${versions.playServices}"
    api "com.google.firebase:firebase-firestore:${versions.playServices}"

    // ----------------------
    // Firebase UI
    // ----------------------

    implementation ('com.firebaseui:firebase-ui-auth:3.2.2') {
        exclude group: 'com.android.support'
    }
}

全球财产

ext {
    versions = [supportLib: "27.1.0",
                playServices: "11.8.0"]
}