Nested Child Fragment with Viewpager

Question

Currently, I am trying to create a nested view pager using a fragment, how can I access top parent function to refresh the View?

Let's say I have:

 public class ParentFragment extends Fragment {

    ...{
    ...
    viewPagerAdapter = new ViewPagerParentAdapter(getChildFragmentManager(), listOfItem);
    viewPager.setAdapter(viewPagerAdapter);
    }

public void refreshView(){
    loadData();
}


private class ViewPagerParentAdapter extends FragmentStatePagerAdapter{
    private List<String> tabTitle;
    private List<Item> listOfItem;
    public ViewPagerParentAdapter(FragmentManager fm, @NonNull List<Item> listOfItem) {
        super(fm);

        this.tabTitle = new ArrayList<>();
        this.listOfItem = new ArrayList<>();

        if (listOfItem.size() > 0) {
            this.listOfItem = listOfItem;

            for (Item item : this.listOfItem) {
                tabTitle.add(Item.getCLASSIFICATION());
            }
        }
        notifyDataSetChanged();
    }

    @Override
    public Fragment getItem(int position) {
        return DetailFragment.newInstance(getItemAtPosition(position).getDETAILS());
    }

     public Item getItemAtPosition(int position) {
        return listOfItem != null ? listOfItem.get(position) : null;
    }
}
}

and here my object

public class Item{
    //POJO
    private String CLASSIFICATION;
    private Details details;
}

detail fragment

public class DetailFragment extends Fragment{

...{
    ...
    Details details = getArguments().getParcelable("details");

    viewPagerAdapter = new DetailViewPagerAdapter(getChildFragmentManager(), details);
    viewPagerDetails.setAdapter(viewPagerAdapter);
}

public void refreshParentView(){
    ((ParentFragment) getParentFragment()).refreshView(); //getting Null
}

public class DetailViewPagerAdapter extends FragmentStatePagerAdapter {

    String[] tabTitle = {"Components", "Materials", "Descriptions"};
    Details details;


    public DetailViewPagerAdapter(FragmentManager fm, @NonNull Details details) {
        super(fm);
        this.details = details;
        notifyDataSetChanged();
    }

    @Override
    public Fragment getItem(int position) {
        switch (position) {
            case 0:
                return DetailsChildFragment.newInstance(details.getCOMPONENT());
            case 1:
                return DetailsChildFragment.newInstance(details.getMATERIAL());
            case 2:
                return DetailsChildFragment.newInstance(details.getDESC());
        }
        return null;
    }

    @Override
    public int getCount() {
        return tabTitle.length;
    }
}
}

last child fragment

public class DetailsChildFragment extends Fragment implements View.OnClickListener{

...{
...
...

Button buttonRefresh = (Button)getView().findViewById(R.id.button_refresh);
buttonRefresh.setOnClickListener(this);
}

@Override
public void onClick(View view){
    switch(view.getId()){
        case R.id.button_refresh:
            ((DetailFragment)getParentFragment()).refreshParentView();
        break;
    }
}

}

Currently I am getting Null on the detail fragment refreshParentView

Any suggestions? Thanks in advance

vlatkozelka · Accepted Answer · 2017-07-17T14:53:31.900

You could use an interface as a Listener for events happening in the child

public interface Listener{
  void onRefreshButtonClicked();
}

The child fragment needs to have a Listener as a field, and then you could set the Listener when getting an instance of the child fragment.

public class ChildFragment extends Fragment{

private Listener listener;

public void setListener(Listener listener)//setter
...

//now on button click you call the listener
refreshButton.setOnClickListener(new View.OnClickListener(){

    @Override onClick(){
        if(listener!=null){
            listener.onRefreshButtonClicked();
        }
    }
}




public class ParentFragment extends Fragment{
    ...


    ChildFragment child = ChildFragment.getInstance()
    child.setListener(new Listener(){
        @Override
        void onRefreshButtonClicked(){
// implement your logic
        }
    }

An advantage of doing it like this is that you don't need to cast the parent from Fragment to ParentFragment which makes your code re-usable should you ever need to

Thanks this is helpful saved my day :D – Aldi Renaldi Gunawan Jul 17 '17 at 14:58 — Aldi Renaldi Gunawan, Jul 17 '17 at 14:58

score 0 · Answer 2 · answered Jul 17 '17 at 13:52

When you add your DetailFragment do it with a tag, so that you can retrieve it's instance when you need it. Example:

getSupportFragmentManager().beginTransaction().add(R.id.fragment_container, detailFragment,"detailFragmentTag").commit();

Now, any time you need to access this fragment, you only need to call

DetailFragment parentFragment = (DetailFragment) getActivity().getSupportFragmentManager().findFragmentByTag("detailFragmentTag");
if(detailFragment != null && detailFragment.isAdded()){ //check if it is not null and it is added to the view so you dont end up in some NPE
    detailFragment.refreshParentView()

thanks for your answer it's correct if access the second parent, but i need to access the top of parent (ParentFragment(this) -> DetailFragment(not this) ->DetailChildFragment), thanks man — Aldi Renaldi Gunawan, Jul 17 '17 at 14:59

Nested Child Fragment with Viewpager

2 Answers2