Android: Callback AsyncTask to Fragment(Not Activity)

Question

I am trying to implement callback between AsyncTask and Fragment but cannot find correct info how to do it. The issue is that all callback implementations are between activity and asynctask but I need between fragment and asynctask. Could someone give me small working example how to implement it without activity. My action structure: Fragment call DialogFragment -> choose something and send server request to async task -> async task process everything and update view and some variables. My main problem is that I call prepareData() only once in onCreate and when I walk between other fragment and returns come back I see old data. That is to say there is not enough to update only view in onPost of asynctask. It will be good to have callback which will update the whole 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);
}

Answer 1

Without taking your code in consideration I will post the most essential to make a functional callback.

---

TestFragment:

public class TestFragment extends Fragment {

    /* Skipping most code and I will only show you the most essential. */    
    private void methodThatStartsTheAsyncTask() {
        TestAsyncTask testAsyncTask = new TestAsyncTask(new FragmentCallback() {

            @Override
            public void onTaskDone() {
                methodThatDoesSomethingWhenTaskIsDone();
            }
        });

        testAsyncTask.execute();
    }

    private void methodThatDoesSomethingWhenTaskIsDone() {
        /* Magic! */
    }

    public interface FragmentCallback {
        public void onTaskDone();
    }
}

---

TestAsyncTask:

public class TestAsyncTask extends AsyncTask<Void, Void, Void> {
    private FragmentCallback mFragmentCallback;

    public TestAsyncTask(FragmentCallback fragmentCallback) {
        mFragmentCallback = fragmentCallback;
    }

    @Override
    protected Void doInBackground(Void... params) {
        /* Do your thing. */
        return null;
    }

    @Override
    protected void onPostExecute(Void result) {
        mFragmentCallback.onTaskDone();
    }
}