Proper way to subclass a Java AsyncTask for looser coupling

Question

What is the proper way to subclass an AsyncTask so that it can be reused in multiple activities?

I have a multiple Activities that all use the same AsyncTask to get some JSON data. The only difference is that each Activity has it's own ProgressBar to show activty and its own processResult for processing the returned JSON data. I would like to subclass the AsyncTask so that I can pass in a reference to a ProgressBar so the appropriate Activity's ProgressBar's visibility is set and pass the returned data to that Activity's processResults().

Here is an abstract of a typical activity:

public class MyActivity extends AppCompatActivity {

    private ProgressBar mProgessBar;
    private List<Object> myList;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.mylayout);


        mProgessBar = (ProgressBar) findViewById(R.id.myProgessBar);
        myList = new ArrayList<Object>();

        getData();

    }

    private void getData() {
        //All async tasks take string variables
            new BGGetData().execute("Something", "Something", "Dark side", null);
    }

    private void processResults(JSONObject data) {
    //Different types of data for different activities.
        //process JSON results to fill myList or do something other action with the data
    }


    ///////
    //BACKGROUND TASK IS REPEATED IN MULTIPLE ACTIVITIES
    ///////
    public class BGGetData extends AsyncTask<String, Void, JSONObject> {

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

        }

        @Override
        protected JSONObject doInBackground(String... params) {

            // do something to get a jsonobject

            return json; 
        }

        @Override
        protected void onPostExecute(JSONObject data) {
            mProgressBar.setVisibility(View.GONE);
            processResults(data);
        }

    }

}