Estoy tratando de implementar la devolución de llamada entre AsyncTask y Fragment pero no puedo encontrar la información correcta sobre cómo hacerlo. El problema es que todas las implementaciones de devolución de llamada son entre actividad y asynctask pero necesito entre fragmento y asynctask. ¿Podría alguien darme un pequeño ejemplo de trabajo de cómo implementarlo sin actividad? Mi estructura de acción: Fragmentar la llamada DialogFragment -> elegir algo y enviar solicitud de servidor a tarea asíncrona -> tarea asíncrona procesar todo y actualizar la vista y algunas variables. Mi principal problema es que llamo a prepareData () solo una vez en onCreate y cuando camino entre otro fragmento y vuelvo, veo datos antiguos. Es decir, no hay suficiente para actualizar solo la vista en onPost de asynctask. Será bueno tener una devolución de llamada que actualizará todas las variables.

public class TermsAndConditionsFragment extends SherlockFragment implements OnClickListener, OnTouchListener, OnItemClickListener, onTaskListener {
 @Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    fm = getSherlockActivity().getSupportFragmentManager();


    prepareData();
}

public void prepareData() {
     termsAndConditionsM = new TermsAndConditionsManager(getSherlockActivity());
    termsAndConditions = termsAndConditionsM.getTermsAndConditions();

    if (termsAndConditions != null) {
                 int totalPayments = Integer.valueOf(termsAndConditions.get(ServerAPI.NO_OF_PAYMENTS));
        if (totalPayments > 0) {
            paymentsData = termsAndConditionsM.getpayments();

            if (paymentsData != null) {

                payments = new ArrayList<Payment>();

                for (int i = 1; i <= totalPayments; i++) {
                    paymentValues = new Payment();
                    paymentValues.setPaymentID(Integer.valueOf(paymentsData.get(ServerAPI.PAYMENT_NO + "_" + i)));
                    paymentValues.setPaymentDate(paymentsData.get(ServerAPI.PAYMENT_DATE + "_" + i));
                    paymentValues.setPaymentTotalAmount(paymentsData.get(ServerAPI.PAYMENT_TOTAL + "_" + i));
                    payments.add(paymentValues);
                }
            }
        }
    }
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

    rootView = init(inflater, container);

    if (payments != null || termsAndConditions != null)
        updateTermsAndConditionsView();

    return rootView;
}

private View init(LayoutInflater inflater, ViewGroup container) {
    rootView = inflater.inflate(R.layout.fragment_terms_and_conditions, container, false);

    ...
    return rootView;
}

public void updateTermsAndConditionsView() {
    etHowMuch.setText("£" + termsAndConditions.get(ServerAPI.AMOUNT_OF_CREDIT));
    etForHowLong.setText(Helpers.ConvertDays2Date(Integer.valueOf(termsAndConditions.get(ServerAPI.TERM_OF_AGREEMENT_IN_DAYS))));

    PaymentAdapter adapter = new PaymentAdapter(getSherlockActivity(), R.layout.custom_loan_item, payments);
    lvPayments.setAdapter(adapter);

    tvNoOfPayments.setText(termsAndConditions.get(ServerAPI.NO_OF_PAYMENTS));
    tvFirstPayment.setText(termsAndConditions.get(ServerAPI.FIRST_PAYMENT_DATE));
    tvTotalRepayable.setText("£" + termsAndConditions.get(ServerAPI.TOTAL_REPAYABLE));
}

@Override
public void onClick(View v) {
    ft = fm.beginTransaction();

    howMuch = etHowMuch.getText().toString();
    forHowLong = etForHowLong.getText().toString();

    switch (v.getId()) {
        case R.id.etHowMuch:
            f = new NumberPaymentsPickerFragment();
            args = new Bundle();
            args.putInt(Const.HOW_MUCH, Integer.valueOf(howMuch.replace("£", "")));
            args.putDouble(ServerAPI.PAYMENT_STEP, Const.PAYMENT_STEP);
            args.putString(Const.STATE, ServerAPI.TERMS_AND_CONDITIONS);
            f.setArguments(args);
            f.setTargetFragment(this, DIALOG_FRAGMENT);
            f.show(getActivity().getSupportFragmentManager(), Const.HOW_MUCH);
            break;
        case R.id.etForHowLong:
            f = new NumberPaymentsPickerFragment();
            args = new Bundle();
            args.putInt(Const.FOR_HOW_LONG, Integer.valueOf(Helpers.ConvertDate2Days(forHowLong)));
            args.putDouble(ServerAPI.PAYMENT_STEP, Const.PAYMENT_STEP);
            args.putString(Const.STATE, ServerAPI.TERMS_AND_CONDITIONS);
            f.setArguments(args);
            f.setTargetFragment(this, DIALOG_FRAGMENT);
            f.show(getActivity().getSupportFragmentManager(), Const.FOR_HOW_LONG);
            break;
        case R.id.tvPersonalDetails:
            sfm.saveCurFragment(ServerAPI.PERSONAL_DETAILS, 0);
            ft.replace(android.R.id.content, new PersonalDetailsFragment(), ServerAPI.PERSONAL_DETAILS).addToBackStack(null).commit();
            break;
        case R.id.tvAgreementDetails:
            sfm.saveCurFragment(ServerAPI.AGREEMENT_DETAILS, 0);
            ft.replace(android.R.id.content, new AgreementDetailsFragment(), ServerAPI.AGREEMENT_DETAILS).addToBackStack(null).commit();
            break;
        case R.id.bApply:

            break;
    }

@Override
public void onUpdateData() {
    Log.d(TAG, "Update data");

}

}

DialogFragment:

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    Bundle args = getArguments();

    ...
}

public Dialog onCreateDialog(Bundle savedInstanceState) {

    ...

        return createDialog(v, R.string.for_how_long, etHowMuch, etForHowLong, etPromotionCode);
    }
    return null;
}
private Dialog createDialog(View view, int titleResID, final EditText howMuchField, final EditText forHowLongField, final EditText promotionCodeField) {
    AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
    builder.setTitle(titleResID);
    builder.setView(view);
    builder.setPositiveButton(R.string.set, new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialog, int id) {

            doShowProgress();

        }

        private void doShowProgress() {


            ExecuteServerTaskBackground task = new
                    ExecuteServerTaskBackground(getActivity());
                task.action = ServerAPI.GET_TERMS_AND_CONDITIONS;
                onTaskListener listener = new onTaskListener() {

                @Override
                public void onUpdateData() {
                    Log.d(TAG, "Updaaate");

                }
            };
            task.setListener(listener);
            task.args = args;
            task.execute();
        }

    }).setNegativeButton(R.string.cancel, new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialog, int id) {
            dialog.cancel();
        }
    });
    return builder.create();
}

AsyncTask:

    onTaskListener mListener;

public interface onTaskListener {
    void onUpdateData();
}

public void setListener(onTaskListener listener){
  mListener = listener;
}
public ExecuteServerTaskBackground(Activity activity) {
    this.mActivity = activity;
    this.mContext = activity.getApplicationContext();
}

@Override
protected void onPreExecute() {
    pb = (ProgressBar) mActivity.findViewById(R.id.progressBar1);
    pb.setVisibility(View.VISIBLE);
}

@Override
protected Void doInBackground(Void... params) {
    ServerAPI server = new ServerAPI(mContext);
    if (!args.isEmpty())
        server.serverRequest(action, args);
    else
        server.serverRequest(action, null);
    return null;
}

@Override
protected void onPostExecute(Void result) {
 mListener.onUpdateData();

//There is I just update view but how to update whole variables throughtout callback?        
//                tvNoOfPayments = (TextView) mActivity.findViewById(R.id.tvNoOfPaymentsValue);
//                tvFirstPayment = (TextView) mActivity.findViewById(R.id.tvFirstPaymentValue);
//                tvTotalRepayable = (TextView) mActivity.findViewById(R.id.tvTotalRepayableValue);
//
//                lvPayments = (ListView) mActivity.findViewById(R.id.lvData);
//
//                termsConditionsM = new TermsAndConditionsManager(mContext);
//
//                termsAndConditions = termsConditionsM.getTermsAndConditions();
//
//                int totalPayments = Integer.valueOf(termsAndConditions.get(ServerAPI.NO_OF_PAYMENTS));
//
//                if (totalPayments > 0) {
//                    if (termsAndConditions != null) {
//                        tvNoOfPayments.setText(termsAndConditions.get(ServerAPI.NO_OF_PAYMENTS));
//                        tvFirstPayment.setText(termsAndConditions.get(ServerAPI.FIRST_PAYMENT_DATE));
//                        tvTotalRepayable.setText("£" + termsAndConditions.get(ServerAPI.TOTAL_REPAYABLE));
//                    }
//
//                    paymentsData = termsConditionsM.getpayments();
//
//                    if (paymentsData != null) {
//                        Log.d(TAG, paymentsData.toString());
//
//                        payments = new ArrayList<Payment>();
//
//                        for (int i = 1; i <= totalPayments; i++) {
//                            paymentValues = new Payment();
//                            paymentValues.setPaymentID(Integer.valueOf(paymentsData.get(ServerAPI.PAYMENT_NO + "_" + i)));
//                            paymentValues.setPaymentDate(paymentsData.get(ServerAPI.PAYMENT_DATE + "_" + i));
//                            paymentValues.setPaymentTotalAmount(paymentsData.get(ServerAPI.PAYMENT_TOTAL + "_" + i));
//                            payments.add(paymentValues);
//                        }
//
//                        PaymentAdapter adapter = new PaymentAdapter(mContext, R.layout.custom_loan_item, payments);
//                        lvPayments.setAdapter(adapter);
//                    }
    //             

   }

    pb.setVisibility(View.GONE);
    super.onPostExecute(result);
}