回到你的位置。在项目级别的Gradle文件中，您会发现以下行突出显示

dependencies {
    classpath 'com.android.tools.build:gradle:3.1.4'  //place your cursor over here 
    //and hit alt+enter and it will show you the appropriate version to select


    // NOTE: Do not place your application dependencies here; they belong
    // in the individual module build.gradle files

    classpath 'com.google.gms:google-services:4.0.2' //the same as previously
}

在我的情况下，问题是谷歌服务gradle插件与以下一行在gradle文件:

应用插件:'com.google.gms.google-services'

删除这个就解决了这个问题

我已经尝试在Android Studio 3.0.1中将谷歌gms服务更改为最新的com.google.gms:google-services:3.2.1，但警告仍然存在。

根据编译器的建议，我将所有编译依赖项更改为实现，并将testCompile更改为testimplemimplementation，如下所示。

dependencies {
implementation fileTree(include: ['*.jar'], dir: 'libs')
implementation 'com.android.support:appcompat-v7:27.1.1'
implementation 'com.android.support:mediarouter-v7:27.1.1'
implementation 'com.android.support:design:27.1.1'
implementation 'com.google.firebase:firebase-ads:12.0.1'
implementation 'com.google.firebase:firebase-crash:12.0.1'
implementation 'com.google.firebase:firebase-core:12.0.1'
implementation 'com.google.firebase:firebase-messaging:12.0.1'
implementation 'com.google.firebase:firebase-perf:12.0.1'
implementation 'com.google.firebase:firebase-appindexing:12.0.1'
implementation 'com.android.support.constraint:constraint-layout:1.0.2'
testImplementation 'junit:junit:4.12'
implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
}

最后，警告被删除!

回到你的位置。在项目级别的Gradle文件中，您会发现以下行突出显示

dependencies {
    classpath 'com.android.tools.build:gradle:3.1.4'  //place your cursor over here 
    //and hit alt+enter and it will show you the appropriate version to select


    // NOTE: Do not place your application dependencies here; they belong
    // in the individual module build.gradle files

    classpath 'com.google.gms:google-services:4.0.2' //the same as previously
}

使用当前最新版本的谷歌gms服务为我解决了这个问题。

在项目级别build.gradle:

buildscript {
    ...
    dependencies {
        classpath 'com.google.gms:google-services:3.2.1'
        ...  
    }
}

不需要拆线。正如Jkrevis所写的，更新com.google。Gms:google-services升级到3.2.0并停止警告。