AdmobFree问题 - 离子

Question

当我尝试构建Ionic 2 / Angular 2项目时出现以下错误：

error: cannot find symbol
        return AdSize.SEARCH;
^
        symbol:   variable SEARCH
        location: class AdSize

FAILURE: Build failed with an exception.

        * What went wrong:
        Execution failed for task ':compileDebugJavaWithJavac'.
        > Compilation failed; see the compiler error output for details.

        * Try:
        Run with --stacktrace option to get the stack trace. Run with --info or
        --debug option to get more log output.

希望有人能帮助我。  我使用以下插件：

https://ionicframework.com/docs/native/admob-free/

谢谢！

编辑： 我猜这个问题是：

导入com.google.android.gms.ads.AdSize;

所以出于某种原因，我的离子项目没有正确地获得谷歌图书馆:(