I have an existing project that was built without gradle for Android Studio
and I\'m trying to get Google Play Services imported to fix a
java.lang.NoClassDefFoundErr
SDK/Extras DirectoryUse your SDK Manager to download the Google Play Services - it'll be found under the Extras directory.
Go to your Android SDK directory and find the google-play-services_lib directory, for me this was in the Android Studio package:
/Applications/Android Studio.app/sdk/extras/google/google_play_services/libproject/google-play-services_lib/
Copy this entire directory to your project's libs directory.
Add this as a module dependency as you normally would. (For Android Studio, see below for step-by-step instructions.)
You'll need to add a meta-tag to your AndroidManifest.xml file as well, that looks like this:
<meta-data android:name="com.google.android.gms.version"
android:value="@integer/google_play_services_version" />
Profit and Party?
Steps to add the library project as a module dependency once it's already in your libs directory.
File > Import Module.
Select the google-play-services_lib directory under your libs directory.
Ensure Create module from existing sources is selected and click Next until you finish the wizard.
Project Structure > Modules (far left) > Select Your App > Dependencies tab > + > Module Dependency > google-play-services_lib.
Project Structure > Modules (far left) > Select google-play-services_lib > Dependencies tab > + > Jars or directories... > Find and select libs/google-play-services_lib/libs/google-play-services.jar.
Make sure you click the Export checkbox for this dependency.

Profit and Party?
Many thanks to Adama Speakman's post for the specific Android Studio steps.
JP