My Firebase Authentication Dependency Issue - android-studio

Question

I added this line of code to my android Manifest in trying to add the Firebase Authentication Dependency:
compile 'com.android.support:appcompat-v7:24.1.1'
compile 'com.android.support:design:24.1.1'
}
apply plugin: 'com.google.gms.google-services'
And this is what the error I keep seeing when I sync the Gradle:
Error:Execution failed for task ':app:processDebugGoogleServices'.
> No matching client found for package name 'ng.org.fafic.fafic'
How do I resolve this error, please?
Now, when I leave my gradle to be like this:
dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
testCompile 'junit:junit:4.12'
compile 'com.android.support:appcompat-v7:24.1.1'
compile 'com.android.support:design:24.1.1'
compile 'com.google.firebase:firebase-auth:9.4.0'
}
My project will compile without any error. It will even allow me to use the Firebase classes for authentication. But when I try to run the app, the app crashes and I am left with this error:
Process: ng.org.fafic.fafic, PID: 24478
java.lang.RuntimeException: Unable to start activity ComponentInfo{ng.org.fafic.fafic/ng.org.fafic.fafic.RegisterActivity}: java.lang.IllegalStateException: FirebaseApp with name [DEFAULT] doesn't exist.
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2808)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2873)
at android.app.ActivityThread.access$900(ActivityThread.java:181)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1482)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:6145)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)
Caused by: java.lang.IllegalStateException: FirebaseApp with name [DEFAULT] doesn't exist.
at com.google.firebase.FirebaseApp.getInstance(Unknown Source)
at com.google.firebase.FirebaseApp.getInstance(Unknown Source)
at com.google.firebase.auth.FirebaseAuth.getInstance(Unknown Source)
at ng.org.fafic.fafic.RegisterActivity.onCreate(RegisterActivity.java:35)
at android.app.Activity.performCreate(Activity.java:6374)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1119)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2752)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2873) 
at android.app.ActivityThread.access$900(ActivityThread.java:181) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1482) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:145) 
at android.app.ActivityThread.main(ActivityThread.java:6145) 
at java.lang.reflect.Method.invoke(Native Method) 
at java.lang.reflect.Method.invoke(Method.java:372) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194) 

Answer 1

> No matching client found for package name 'ng.org.fafic.fafic'
This error happens when the google-services.json is missing in your build.
Also check if the package_name in the google-services.json has a correct value according to your package name.
{
"project_info": {
},
"client": [
{
"client_info": {
"android_client_info": {
"package_name": "xxxxxxxxxx"
}
...
}

Answer 2

As i've seen from your replies with #Gabriele, Please check with me as the following.
First, Check if you've already downloaded the SDK for using Google Play Services/Firebase .
After checking, you need to add Google play services lib in your build.gradle app's level, and the firstbase, for me i used the messaging one too :
compile 'com.google.android.gms:play-services:9.2.1'
compile 'com.google.firebase:firebase-messaging:9.0.1'
compile 'com.google.firebase:firebase-core:9.2.1'
And in the last line ( out of all brackets {} ), you need to add this :
apply plugin: 'com.google.gms.google-services'
Now, in your build.gradle Project's level, you need to add this inside 'dependencies' brackets
classpath 'com.google.gms:google-services:3.0.0'
the most important piece is your json file, download the json file and navigate to your project/your-app folder and paste it there, your app folder is the folder that contain files/folders like src/libs/build etc ..