onSuccess.java

@Override
public void onSuccess(LoginResult loginResult) {
    mDialog = new ProgressDialog(MainActivity.this);
    mDialog.setMessage("Retrieving data...");
    mDialog.show();

    String accessToken = loginResult.getAccessToken().getToken();

    GraphRequest request = GraphRequest.newMeRequest(loginResult.getAccessToken(), new GraphRequest.GraphJSONObjectCallback() {
        @Override
        public void onCompleted(JSONObject object, GraphResponse response) {
            mDialog.dismiss();

            Log.d(TAG, "onCompleted: " + object.toString());
            
            getData(object);
        }
    });

    //Request Graph API
    Bundle parameters = new Bundle();
    parameters.putString("fields", "id, email, location, birthday, friends");
    request.setParameters(parameters);
    request.executeAsync();
}