runOnUiThread is not running in AsyncTask

runOnUiThread is a method of Activity, AsyncTask has no reference to Activity.

however, AsyncTask already runs on the UI thread and was designed to do exactly that.

just deal with the UI changes in onPostExecute.

Try this way :

First create one Handler :

Handler mHandler = new Handler();

Change this,

public void commentBuilder()
    {
        runOnUiThread(new Runnable() // while debugging, it comes here, on Step Over it stick for 2 times and then move at the end of method without error 
        {       
            public void run() 
            {
                // update UI code
            }
        });
    }

With,

public void commentBuilder()
    {
        new Thread(new Runnable() {
            @Override
            public void run() {
                // TODO Auto-generated method stub
                while (isRunning) {
                    try {
                       // Thread.sleep(10000);
                        mHandler.post(new Runnable() {

                            @Override
                            public void run() {
                                // TODO Auto-generated method stub
                                // Write your code here to update the UI.                               
                            }
                        });
                    } catch (Exception e) {
                        // TODO: handle exception
                    }
                }
            }
        }).start();
    }

Stop thread by this once you are done with UI,

isRunning = false;

EDIT :

Try to Use Async Task in this way :

class parseComments extends AsyncTask<String, Integer,String> 
    {
        protected String doInBackground(String... params) {
            String parseComReturn = parseComments();
            return parseComReturn;
        }

        protected void onPostExecute(String result) {
            if(result.equals("end"))
            {
                commentBuilder();
            }
        }
    }

Thanks.