How to add Polyline to google map and show progress dialog in that time?

Question

I want to show progress bar while polyline will be drawing on the screen. I know that Polyline is drawing only in UI thread. I have tried nextcode, but this doesn't helps. There was not progress dialog

 final Handler mHandler = new Handler();

                    class shpLoading extends AsyncTask<Void, Void, Void> {
                        ProgressDialog dialog;

                        @Override
                        protected Void doInBackground(Void... params) {
                            mHandler.post(new Runnable() {
                                public void run() {
                                    googleMap.addPolyline(new PolylineOptions()
                                            .addAll(mRoutePoints)
                                            .width(3)
                                            .color(Color.RED));
                                }
                            });
                            return null;
                        }

                        @Override
                        protected void onPreExecute() {
                            Log.d("myLogs", "onPreExecute");
                            dialog = new ProgressDialog(getActivity());
                            dialog.setMessage("Kraunama...");
                            dialog.setIndeterminate(true);
                            dialog.setCancelable(false);
                            dialog.show();
                        }

                        @Override
                        protected void onPostExecute(Void result) {
                            Log.d("myLogs", "onPostExecute");
                            dialog.dismiss();
                        }
                    }

                    shpLoading shpLoading = new shpLoading();
                    shpLoading.execute();