How to retain listener on custom dialog opened from fragment?

Question

I have run into a bit of a roadblock. I have a scenario VERY similar to the one described at: DialogFragment - retaining listener after screen rotation

The proposed solution works fine for the author because his dialog is being called from an activity. My case is the exact same, but my Custom Dialog is called from a Fragment instead of an Activity. (IE Activity->Fragment->Dialog)

I implemented the same solution (setting the listener in onResume from the calling Fragment) but it doesn't work in this case.

What seems to be happening is that when the screen is rotated, Android kills the Dialog and Fragment. Then recreates them IN THAT ORDER. So when my onCreateDialog is called on my custom dialog the containing Fragment is yet to be recreated, so it has null for the listener to set for positive and negative buttons.

Does anyone know a way around this?

public class RecipeDetailEditFragment extends SherlockFragment implements DialogInterface.OnClickListener {
    private EditStepFragmentDialog stepDialog;
    private Recipe newRecipe; //main data object implements parcelable
    ...
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        ...
        stepDialog = EditStepFragmentDialog.newInstance(newRecipe);
        //I've also tried passing 'this' into the newInstance constructor and 
        //setting the listener there, but that doesn't work either
    }

    public void onResume() {
        stepDialog.setListener(this);
        super.onResume();
    }
    ...
}


public class EditStepFragmentDialog extends DialogFragment {
    private DialogInterface.OnClickListener ocl;
    private static final String ARG_RECIPE = "recipe";
    private Recipe recipe;

    public EditStepFragmentDialog() {}

    public static EditStepFragmentDialog newInstance(Recipe rec) { //(Recipe rec, DialogInterface.OnClickListener oc) as mentioned doesn't work.
        EditStepFragmentDialog dia = new EditStepFragmentDialog();
        Bundle args = new Bundle();
        args.putParcelable(ARG_RECIPE, rec);

        //dia.setListener(oc);
        return dia;
    }

    public Dialog onCreateDialog(Bundle savedInstanceState) {
        AlertDialog.Builder adb = new AlertDialog.Builder(getActivity());

        if (getArguments().containsKey(ARG_RECIPE)) {
            recipe = (Recipe) getArguments().getParcelable(ARG_RECIPE);
        }
        ...

        adb.setPositiveButton("Done", ocl);
        adb.setNegativeButton("Cancel", ocl);

        ...

        return adb.create();
    }

    public void setListener(DialogInterface.OnClickListener cl) {
        ocl = cl;
    }
}

Answer 1

I ran through all of the options on the discussed links and none of the solutions ended up working for me. I also tried a number of additional options after further googling like get/setTargetFragment, and FragmentManager.put/getFragment. These didn't work for me either. Then I took another look at:

http://developer.android.com/training/basics/fragments/communicating.html

Where they specifically say "Two Fragments should never communicate directly". I think this is one of the cases where that's really proven true.

I ended up implementing the suggested callback mechanism provided there and ended up with this:

In DialogFragment:

public interface OnEditStepDialogListener {
    public void onEditStepDialogPositive(int pos, String description);
}

@Override
public void onAttach(Activity activity) {
    super.onAttach(activity);

    try {
        mCallback = (OnEditStepDialogListener) activity;
    } catch (ClassCastException e) {
        throw new ClassCastException(activity.toString() + " must implement OnEditStepDialogListener");
    }
}

In hosting Activity:

public class MyActivity extends SherlockFragmentActivity implements EditStepFragmentDialog.OnEditStepDialogListener {

...

@Override
public void onEditStepDialogPositive(int pos, String desc) {
    FragmentManager fm = getSupportFragmentManager();
    RecipeDetailEditFragment ef = (RecipeDetailEditFragment)fm.findFragmentByTag(RecipeDetailEditFragment.TAG);

    ef.applyStepEdit(pos, desc);
}

In Fragment that fires off the FragmentDialog:

public static final String TAG = "tag1";

public void applyStepEdit(int pos, String description) {
    ...
}

This works perfectly, if opened then orientation change and edit is completed, it actually triggers the ultimate function I need run in the calling Fragment instead of either crashing or not doing anything (null listener).

Answer 2

Would it be a disaster to report back to your activity and make that create the dialog?

I just reviewed my code to see what I am doing as I have not encountered this problem. My take on it is something like this:

- MyActivity
     |
     ---- MapsFragmet (for example)
     |
     ---- DirectionsModule (simple class that is handed Context)
     |
     ---- PointsOfInterestModule (simple class that is handed Context)

Thus with this construction the activity uses the fragment purely to show the map but can use it for both the purpos of directions, or points of interest, depending on which Module is invoked.

Now when the module encounter a problem, or needs userinteraction, it reports back to MyActivity, which then for instance displays a DialogFragment.

Would like to give a better answer, as I dont see why you should not be able to invoke a DialogFragment from within another Fragment and expect a nice behaviour.

Just in case, have you set setRetainInstance(true) on you Fragment?

Edit:

Ok, so I just reviewed your newly commited code, here is my new idea:

Extend the arguments of your dialog to take a context so u can call it like this:

stepDialog = EditStepFragmentDialog.newInstance(getActivity(), newRecipe);

Next use the the added context instead of getActivity() in your Dialog:

AlertDialog.Builder adb = new AlertDialog.Builder(context);

I suspect (not sure about this) that SherlockFragment counts as an instance of Activity, so when you call getActivity() in your dialog, it is tied to your fragment.