Getting Exception java.lang.NoClassDefFoundError: com.google.firebase.FirebaseOptions after updating to the new firebase

This worked for me:

1. If you haven't already, update your 'Google Play Services' to Revision 30 from Android SDK Manager > Extras.

2. And then add the line compile 'com.android.support:multidex:1.0.1' to your dependancies (or simply remove multiDexEnabled true if not required)

3. Add this attribute to the application tag in manifest: android:name="android.support.multidex.MultiDexApplication"
   If you already have a custom application class defined in Android Manifest, extend it from MultiDexApplication instead of Application

Hope it helped!

Using latest Google Play services but was not working. For me this procedure is working:

1. Updated my Application class:

   public class App extends Application {
     @Override
     protected void attachBaseContext(Context base) {
       super.attachBaseContext(base);
       MultiDex.install(this);
    }
   }
   

2. Updated build.gradle file:

   defaultConfig {
       ...
       multiDexEnabled true
   }
   

3. Included dependencies:

   dependencies {
     compile 'com.android.support:multidex:1.0.0'
   }
   

It is so simple to fix guys.If you are using player-services and firebase both in your project make sure that you don't import all the available services in the google.Just import the APIs what you actually need. For example:

 compile 'com.google.firebase:firebase-messaging:9.2.0'
 compile 'com.google.android.gms:play-services:9.2.0'

Doing this way it can give you noclassdeffounderror .To fix this

remove play-services and sync your project. If you have dependency like using ads or maps in your app then define the specific API. like:

compile 'com.google.android.gms:play-services-maps:9.2.0'

Note: Maximum don't try to use multiDexEnabled true. This should be your last step to fix something.

Hope this is helpful.