Unable to initiate post request with json body

[dkch]

I'm using this library to access oAuth 1.0 authenticated xero API, it's working fine in GET request so I'm able to get user's data. But it's not working with POST request so I'm unable to update anything it's always throwing 400 bad request but same request working with postman.

com.google.api.client.googleapis.json.GoogleJsonResponseException: 400 Bad Request
                                                                                    at com.google.api.client.googleapis.services.json.AbstractGoogleJsonClientRequest.newExceptionOnError(AbstractGoogleJsonClientRequest.java:113)
                                                                                    at com.google.api.client.googleapis.services.json.AbstractGoogleJsonClientRequest.newExceptionOnError(AbstractGoogleJsonClientRequest.java:40)
                                                                                    at com.google.api.client.googleapis.services.AbstractGoogleClientRequest$1.interceptResponse(AbstractGoogleClientRequest.java:321)
                                                                                    at com.google.api.client.http.HttpRequest.execute(HttpRequest.java:1056)
                                                                                    at com.google.api.client.googleapis.services.AbstractGoogleClientRequest.executeUnparsed(AbstractGoogleClientRequest.java:419)
                                                                                    at com.google.api.client.googleapis.services.AbstractGoogleClientRequest.executeUnparsed(AbstractGoogleClientRequest.java:352)
                                                                                    at com.google.api.client.googleapis.services.AbstractGoogleClientRequest.execute(AbstractGoogleClientRequest.java:469)
                                                                                    at com.kelltontech.aibconnectorapp.presenter.syncing.SyncPresenter$1.doInBackground(SyncPresenter.java:52)
                                                                                    at com.kelltontech.aibconnectorapp.presenter.syncing.SyncPresenter$1.doInBackground(SyncPresenter.java:40)
                                                                                    at android.os.AsyncTask$2.call(AsyncTask.java:304)
                                                                                    at java.util.concurrent.FutureTask.run(FutureTask.java:237)
                                                                                    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1133)
                                                                                    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:607)
                                                                                    at java.lang.Thread.run(Thread.java:761)