How to use the Shortener API Client Library for Java in Android Studio?

Question

How to use the Shortener API Client Library for Java in Android Studio?

I am using Google+ to login to an android app and I want to send an authentication token to my web server. I am following the link [ https://developers.google.com/identity/sign-in/android/backend-auth] [1 ] and use the following code to generate idToken.

private class GetIdTokenTask extends AsyncTask<String, Void, String> {

    @Override
    protected String doInBackground(String... params) {
        String accountName = Plus.AccountApi.getAccountName(mGoogleApiClient);
        Account account = new Account(accountName, GoogleAuthUtil.GOOGLE_ACCOUNT_TYPE);
        String scopes = "audience:server:client_id:" + Constants.SERVER_CLIENT_ID; // Not the app client ID.
        String idToken = "";
        try {
            idToken = GoogleAuthUtil.getToken(getApplicationContext(), account, scopes);
        } catch (IOException e) {
            Log.e(TAG, "Error retrieving ID token.", e);
        } catch (GoogleAuthException e) {
            Log.e(TAG, "Error retrieving ID token.", e);
        }
        return idToken;
    }

    @Override
    protected void onPostExecute(String result) {
        authToken=result;
        Log.i(TAG, "ID token: " + result);

    }

}

and I am getting the id like this:

eyJhbGciOiJSUzI1NiIsImtpZCI6IxxxxxNThkODVjODU3hiMjI3MjBhM2E1NWxxxxzM0NDcifQ.eyJpc3MiOiJhY2NvdW50cy5nb29nbGUuY29tIiwic3ViIjoiMTEyMzA2OTkwMjA1NDYyMjkzMDExIiwiYXpwIjoiNDU5NTM4MTI1OTIzLXUzNTEzNGZ0aTZyOWJnNGM4MDFjZW82MzVhNWVoNTZzLmFwcHMuZ29vZ2xldXNlcmNvbnRlbnQuY29tIiwiZW1haWwiOiJsZWppbmtyQGdtYWlsLmNvbSIsImVtYWlsX3ZlcmlmaWVkIjp0cnVlLCJhdWQiOiI0NTk1MzgxMjU5MjMtNDZlN3Q3YzNhbmQ3M2VqcThyZWZvZTFzYTIzdm9wOHEuYXBwcy5nb29nbGV1c2VyY29udGVudC5jb20iLCJpYXQiOjE0MzI2MzI5ODUsImV4cCI6MTQzMjYzNjU4NX0.vCT8lanz5Pa2_m_AQ4tZHaME_y_ffa5zqA5_O3u7ZhuOQTmK8xXUh7M-Q_R67KosGPX-ikr_7Tz57OiXNIyKtNBOFKssssxxE0v7wEJvFhVgLSpbuD

is this the real idToken format?

but my back end server authentication token needs a format like this (some other people make the end)

ya29.QwGqNA9LsssggddjKZxxRD74HT_viU0wHxoDieWbsIJG3R0xvW3bDij4jzxxxxxP6wPSi7w1bysA

and the code terminators suggest that I use something like urlshortener and userinfo.email to get such a token. How can I get this token? I am using GoogleApiClient to connect to google plus and drive api in the following code:

if (mGoogleApiClient == null) {
            mGoogleApiClient = new GoogleApiClient.Builder(this)
                    .addApi(Drive.API)
                    .addScope(Drive.SCOPE_FILE)
                    .addApi(Plus.API)
                    .addScope(new Scope("profile"))
                    .addScope(Drive.SCOPE_APPFOLDER) // required for App Folder sample
                    .addConnectionCallbacks(this)
                    .addOnConnectionFailedListener(this)
                    .build();
        }

        findViewById(R.id.sign_in_button).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                mGoogleApiClient.connect();

            }
        });