sinch library 3.12.2 managed push notification error

Question

I had an error while trying to migrate to FireBase managed push, I tried using class FCMservice as the push app in samples but my app crashes giving this log:

FATAL EXCEPTION: AsyncTask #3
                                                                   Process: com.galsa.example, PID: 17415
                                                                   java.lang.RuntimeException: An error occurred while executing doInBackground()
                                                                       at android.os.AsyncTask$3.done(AsyncTask.java:318)
                                                                       at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:354)
                                                                       at java.util.concurrent.FutureTask.setException(FutureTask.java:223)
                                                                       at java.util.concurrent.FutureTask.run(FutureTask.java:242)
                                                                       at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:243)
                                                                       at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1133)
                                                                       at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:607)
                                                                       at java.lang.Thread.run(Thread.java:762)
                                                                    Caused by: java.lang.IllegalStateException: Default FirebaseApp is not initialized in this process com.galsa.example. Make sure to call FirebaseApp.initializeApp(Context) first.
                                                                       at com.google.firebase.FirebaseApp.getInstance(Unknown Source)
                                                                       at com.google.firebase.iid.FirebaseInstanceId.getInstance(Unknown Source)
                                                                       at com.sinch.android.rtc.internal.client.fcm.FcmTask.doInBackground(Unknown Source)
                                                                       at com.sinch.android.rtc.internal.client.fcm.FcmTask.doInBackground(Unknown Source)
                                                                       at android.os.AsyncTask$2.call(AsyncTask.java:304)
                                                                       at java.util.concurrent.FutureTask.run(FutureTask.java:237)
                                                                       at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:243) 
                                                                       at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1133) 
                                                                       at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:607) 
                                                                       at java.lang.Thread.run(Thread.java:762)

Answer 1

first you need to add this line in your dependencies in your root gradle file:

classpath 'com.google.gms:google-services:3.1.0'

then you have to add this line in dependencies in your project gradle file:

implementation 'com.google.firebase:firebase-messaging:11.6.0'

and also add this line at the end of your project gradle file:

apply plugin: 'com.google.gms.google-services'

then you have to follow the steps in this link to generate google-services.json file and put it in the root folder of your project.