saveCredentialsRequest.kt

private val activityResultSubject = PublishSubject.create<ActivityResult>()

fun saveCredentialsRequest(credentialsToSave: Credential): Completable {
    return Completable.create { emitter ->
        Auth.CredentialsApi
            .save(googleApiClient, credentialsToSave)
            .setResultCallback { result ->
                val status = result.status
                if (status.isSuccess) {
                    emitter.onComplete()
                } else if (status.hasResolution()) {
                    try {
                        val disposable = activityResultSubject
                            .filter { it.requestCode == REQUEST_CODE_STORE_CREDENTIALS }
                            .subscribe { handleSaveCredentialsResult(it.resultCode, emitter) }
                        emitter.setDisposable(disposable)

                        val activity = googleApiClient?.context as Activity
                        status.startResolutionForResult(activity, REQUEST_CODE_STORE_CREDENTIALS)
                    } catch (e: IntentSender.SendIntentException) {
                        emitter.onError(Exception("Save credential startResolutionForResult failed: $e"))
                    }
                } else {
                    emitter.onError(Exception("Credentials cannot be saved for ${credentialsToSave.id}"))
                }
            }
    }
}