Listen Dialog Positive button click in each ViewPager fragment

Sam Chen :

I'm testing a function of listening the AlertDialog button click (Positive & Neutral) in each ViewPager fragment. And I am using the Interface method right now but getting some troubles.

So the structure is like this, I have an AlertDialog created by DialogFragment, and I put a ViewPager with two fragments into this DialogFragment. My goal is, when I click on the Positive button on the AlertDialog, I want some methods inside those two ViewPager fragments get called so that I can collect the data on those fragments.

Now the problem is, only the second fragment responses, I don't know why.

Here are the codes:

1. I created an Interface file

   public interface Communicator {
       void onConfirmClick();
   }
   

2. I have a DialogFragment

   public class MainDialogFragment extends DialogFragment {
       View dialogLayout;
       Communicator communicator;
   
       @Override
       public void onAttachFragment(Fragment childFragment) {
           communicator = (Communicator) childFragment;
       }
   
       @Nullable
       @Override
       public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
           return dialogLayout;
       }
   
       @NonNull
       @Override
       public Dialog onCreateDialog(@Nullable Bundle savedInstanceState) {
           AlertDialog.Builder dialogBuilder = new AlertDialog.Builder(getActivity());
           dialogLayout = getActivity().getLayoutInflater().inflate(R.layout.dialog_main, null);
           ViewPager viewPager = dialogLayout.findViewById(R.id.main_viewPager);
   
           final MainPagerAdapter adapter = new MainPagerAdapter(getChildFragmentManager());
           viewPager.setAdapter(adapter);
   
           dialogBuilder.setView(dialogLayout);
           dialogBuilder.setPositiveButton("Confirm", null);
           dialogBuilder.setNegativeButton("Cancel", null);
           dialogBuilder.setNeutralButton("Change", null);
   
           final AlertDialog dialog = dialogBuilder.create();
   
           dialog.setOnShowListener(new DialogInterface.OnShowListener() {
               @Override
               public void onShow(DialogInterface dialogInterface) {
                   dialog.getButton(DialogInterface.BUTTON_POSITIVE).setOnClickListener(new View.OnClickListener() {
                       @Override
                       public void onClick(View view) {
                           communicator.onConfirmClick();
                       }
                   });
   
           dialog.getButton(DialogInterface.BUTTON_NEUTRAL).setOnClickListener(new View.OnClickListener() {
                       @Override
                       public void onClick(View view) {
                           Toast.makeText(view.getContext(), "Change click!!", Toast.LENGTH_SHORT).show();
                       }
                   });
               }
           });
   
           return dialog;
       }
   }
   

3. My fragment A

   public class MainFragmentA extends Fragment implements Communicator{
       View rootView;
   
       @Nullable
       @Override
       public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
           rootView = inflater.inflate(R.layout.fragment_a, container, false);
   
           return rootView;
       }
   
       @Override
       public void onConfirmClick() {
           Toast.makeText(getContext(), "Fragment A!!", Toast.LENGTH_SHORT).show();
       }
   }
   

4. My fragment B

   public class MainFragmentB extends Fragment implements Communicator{
       View rootView;
   
       @Nullable
       @Override
       public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
           rootView = inflater.inflate(R.layout.fragment_b, container, false);
   
           return rootView;
       }
   
       @Override
       public void onConfirmClick() {
           Toast.makeText(getContext(), "Fragment B!!", Toast.LENGTH_SHORT).show();
       }
   }
   

5. My ViewPager adapter used inside DialogFragment

   public class MainPagerAdapter extends FragmentPagerAdapter {
       public MainPagerAdapter(FragmentManager fragmentManager) {
           super(fragmentManager);
       }
   
       @Override
       public Fragment getItem(int position) {
           switch (position) {
               case 0:
                   return new MainFragmentA();
   
               case 1:
                   return new MainFragmentB();
   
               default:
                   throw new IllegalArgumentException("Wrong position!!");
           }
       }
   
       @Override
       public int getCount() {
           return 2;
       }
   }
   

6. My MainActivity

   public class MainActivity extends AppCompatActivity{
       Button showDialogButton;
   
       @Override
       protected void onCreate(Bundle savedInstanceState) {
           super.onCreate(savedInstanceState);
           setContentView(R.layout.activity_main);
   
           showDialogButton = findViewById(R.id.main_show_dialog_button);
   
           showDialogButton.setOnClickListener(new View.OnClickListener() {
               @Override
               public void onClick(View view) {
                   MainDialogFragment mainDialogFragment = new MainDialogFragment();
                   mainDialogFragment.show(getSupportFragmentManager(), "mainDialogFragment");
               }
           });
       }
   }
   

Anyone can help? I'll so appreciate that!!!

Bartek Lipinski :

Use a collection of some sort of Communicator interfaces instead of a single one. You're overwriting the communicator every time a child fragment is attached.

public class MainDialogFragment extends DialogFragment {
    View dialogLayout;
    List<Communicator> communicators = new ArrayList<>();

    @Override
    public void onAttachFragment(Fragment childFragment) {
        communicators.add((Communicator) childFragment);
    }

    // all the other things from the MainDialogFragment...
}

And in the BUTTON_POSITIVE callback iterate through the list.

dialog.getButton(DialogInterface.BUTTON_POSITIVE).setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
        for (Communicator communicator : communicators) { 
            communicator.onConfirmClick();
        }
    }
});