如何在适配器和视图持有者之间创建接口

Question

I want to create an interface between an adapter and a view holder (this view holder is an inner class of another adapter) so that I can update the text view (number). How can I do this?

In detail:

I have two recycle views (Main List Recycler View and Sub List Recycler View horizontally placed as shown in the fig) one having a number (as one of its item) and other having checkbox (as its item).

I have two adapters FilterMainListAdapter and FilterSubListAdapter with view holders FilterMainListViewHolder and FilterSubListViewHolder populating the fields.

When checkboxes are selected in the Sub List Recycler View, I want the corresponding number in the Main List Recycler View to update.

For this, I'm using and Interface.

public interface ChangeFilterMainNumber {
void OnChangeFilterMainNumberListener(int totalCheckedNumber);
}

I've checkbox's onClick method inside the FilterSubListViewHolder and I'm trying to send the total check boxes checked number as follows.

changeFilterMainNumber.OnChangeFilterMainNumberListener(totalCheckedNumber);

After that, I'm implementing ChangeFilterMainNumber interface inside the FilterMainListViewHolder

public class FilterMainListViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener,
ChangeFilterMainNumber {...}

But How can I define this interface inside the FilterSubListAdapter ?

changeFilterMainNumber = ???;

[If it is an activity one can define the interface like this changeFilterMainNumber = (ChangeFilterMainNumber) context inside the default constructor of FilterSubListAdapter . But what about a view holder that is an inner class of another adapter?]

or is there a better approach in finding a solution to my problem other than this?

Update: You can take a look at the code here https://github.com/gSrikar/FilterScreen

Answer 1

If I implement the function as you want, I will implement like this: (This is like an Observer pattern)

class Fragment/Activity implement OnChangeFilterMainNumberListener{
    FilterMainListAdapter mainAdapter;
    FilterSubListAdapter subAdapter;

    void oncreate() {
         mainAdapter = new FilterMainListAdapter(this);

    }

    @Override
    void OnChangeFilterMainNumberListener(int totalCheckedNumber) {
          .....
         // Update data to sub list
    }
}

class FilterMainListAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder>{

    public interface ChangeFilterMainNumber {
          void OnChangeFilterMainNumberListener(int totalCheckedNumber);
     }
    ChangeFilterMainNumber listener;
    FilterMainListAdapter(ChangeFilterMainNumber listener) {
         this.listener = listener;
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        item.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    if(listener != null) {
                            listener.OnChangeFilterMainNumberListener(position)
                    }
                }
            });
    }

}

class FilterSubListAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder>{


}