// An AsyncTask definition
// The view in your UI that you want to update from the AsyncTask

private ProgressBar asyncProgress;
private TextView asyncTextView;

private class MyAsyncTask extends AsyncTask<String, Integer, String> {
    @Override
    protected String doInBackground(String... parameter) {
        // Move to a background thread
        String result = "";
        int myProgress = 0;

        int inputLength = parameter[0].length();

        // perform background processing task, update myProgress
        for(int i = 1; i <= inputLength; i++) {
            myProgress = i;
            result = result + parameter[0].charAt(inputLength - i);
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) { }
            publishProgress(myProgress);
        }
        // return the value to be passed to onPostExecute
        return result;
    }

    @Override
    protected void onPreExecute() {
        asyncProgress.setVisibility(View.VISIBLE);
    }

    @Override
    protected void onProgressUpdate(Integer... progress) {
        asyncProgress.setProgress(progress[0]);
    }

    @Override
    protected void onPostExecute(String result) {
        asyncProgress.setVisibility(View.GONE);
        asyncTextView.setText(result);
    }
}