How to call member function of a class that extend DialogFragment in an Activity

Question

I have written custom DatePickerDialog which extends DialogFragment and implements DatePickerDialog.OnDateSetListener.

public class DatePickerFragment extends DialogFragment implements DatePickerDialog.OnDateSetListener {

  @Override
  public Dialog onCreateDialog(Bundle savedInstanceState) {
    DatePickerDialog dpd = new DatePickerDialog(getActivity(),
                R.style.MyDialogTheme, this, year, month, day);
    return dpd;
  }

  public void onDateSet(DatePicker view, int year, int month, int day) {

  }

  // own  methods
  String getFormattedDate() {
  }
}

and I call this fragment in my MainActivity.

public class Booking_activity extends AppCompatActivity implements View.OnClickListener {

  public void onClick(View view) {
    if (view == imgView_from) {
      // Initialize a new date picker dialog fragment
      DialogFragment dFragment = new DatePickerFragment();
      // Show the date picker dialog fragment
      dFragment.show(getFragmentManager(), "Date Picker");

      // error 
      dFragment.getFormattedDate();
    } 
  } 
}

ישו אוהב אותך · Accepted Answer · 2016-12-25T03:41:22.963

The error happens because you try to accessing a not valid method from DialogFragment. You need to create DatePickerFragment with:

DatePickerFragment dFragment = new DatePickerFragment();

Or casting it:

DialogFragment dFragment = new DatePickerFragment();
((DatePickerDialog)dFragment).getFormattedDate();

But the major flaw is, you try to accessing the getFormattedDate() method before the dFragment object has finish instantiated. Remember that show() is an asynchronous call.

So you need to inform the Booking_activity activity when the dFragment has finish instantiated. You can use an interface for it. Something like the following:

In your DatePickerFragment, add interface:

public class DatePickerFragment extends DialogFragment implements DatePickerDialog.OnDateSetListener {

  private DatePickerListener mListener;

  public interface DatePickerListener {
    void onDialogFinishInitialized();
  }

  @Override
  public Dialog onCreateDialog(Bundle savedInstanceState) {
    DatePickerDialog dpd = new DatePickerDialog(getActivity(),
            R.style.MyDialogTheme, this, year, month, day);

    // you need to inform the activity when Dialog has finish
    // initialized.
    mListener.onDialogFinishInitialized();

    return dpd;
  }

  ...

  // Need to add the activity as the listener.
  @Override 
  public void onAttach(Activity activity) {
    super.onAttach(activity);
    // This makes sure that the container activity has implemented
    // the listener interface. If not, it throws an exception
    try {
      mListener = (DatePickerListener) activity;
    } catch (ClassCastException e) {
      throw new ClassCastException(activity.toString() + " must implement DatePickerListener");
    }
  }

  ...

}

Implement the interface in your Activity and call the getFormattedDate() method:

public class Booking_activity extends AppCompatActivity
implements View.OnClickListener, DatePickerFragment.DatePickerListener {
  ...
  private DatePickerFragment dFragment;
  ...
  @Override
  public void onDialogFinishInitialized() {
    // You can call the method here now
    dFragment.getFormattedDate();
  }
  ...
}

score 1 · Answer 2 · edited Dec 25 '16 at 07:58

You need to initialize a new date picker dialog fragment with:

DatePickerFragment dFragment = new DatePickerFragment();

Like in the following code:

public class Booking_activity extends AppCompatActivity implements View.OnClickListener {
  public void onClick(View view) {
    if (view == imgView_from) {

      // Initialize a new date picker dialog fragment
      DatePickerFragment dFragment = new DatePickerFragment(); // Changed this

      // Show the date picker dialog fragment
      dFragment.show(getFragmentManager(), "Date Picker");

      // error 
        dFragment.getFormattedDate();
    } 
  }
}

score 0 · Answer 3 · answered Dec 24 '16 at 17:20

0

you can call the member functions by simply casting the object like shown below

((DatePickerDialog)dFragment).getFormattedDate();

answered Dec 24 '16 at 17:20

Hasif Seyd

1,686
12
19

score 0 · Answer 4 · answered Dec 24 '16 at 17:54

0

Make your function getFormattedDate access mode to public like below

  public String getFormattedDate() {
        }

will solve your problem.

answered Dec 24 '16 at 17:54

Amit Bhati

1,405
12
20

a_lovelace · Answer 5 · 2017-07-17T18:58:58.977

0

The selected solution works well, but I wanted to point out that the onAttach() function is deprecated. I found some solutions here: Android Fragment onAttach() deprecated

I think the most popular answer was this:

@Override
public void onAttach(Context context) {
    super.onAttach(context);
    activity = getActivity();
}

They are changing onAttach(Activity activity) to onAttach(Context context).

edited Jul 17 '17 at 18:58

answered Jul 17 '17 at 17:09

a_lovelace

490
4
11

How to call member function of a class that extend DialogFragment in an Activity

5 Answers5