嵌套适配器的Android notifyDataSetChanged不起作用

Question

In my SectionsListAdapter adapter i have nested Adapter named MonthLessonsList , after get date from web service and set new data and call notifyDataSetChanged method for adapter, main adapter as SectionsListAdapter can be refresh, but nested adapter dont refresh and after calling notifyDataSetChanged for that, doesn't work correctly and don't show new data

call and set new data from Fragment :

monthSectionsItems = SQLite.select().from(MonthSections.class).queryList();
adapter.setData(monthSectionsItems);

and my Adapter with nested adapter:

public class SectionsListAdapter extends RecyclerView.Adapter<SectionsListAdapter.MyViewHolder> {

    private final OnItemSelected listener;
    private List<MonthSections> list;
    private Context context;
    private MonthLessonsList lessonsListAdapter;

    public SectionsListAdapter(List<MonthSections> followingsList, Context mContext, OnItemSelected listener) {
        this.list = followingsList;
        this.context = mContext;
        this.listener = listener;
    }

    @Override
    public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View itemView = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.sections_list_row, parent, false);

        return new MyViewHolder(itemView);
    }

    @Override
    public void onBindViewHolder(@NonNull final MyViewHolder holder, final int position) {
        holder.indicatorIcon.setText(list.get(position).getSection_month_name());
        ...

        List<SectionLesson> lessonsList = list.get(position).getLessons();
        lessonsListAdapter = new MonthLessonsList(lessonsList);
        RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(context);
        holder.userChildCategories.setLayoutManager(mLayoutManager);
        holder.userChildCategories.setAdapter(lessonsListAdapter);

        ...
    }

    @Override
    public int getItemCount() {
        return list.size();
    }

    public void setData(List<MonthSections> data) {
        list.clear();
        list.addAll(data);
        notifyDataSetChanged();
        lessonsListAdapter.notifyDataSetChanged();
    }

    public List<MonthSections> getData() {
        return list;
    }

    class MyViewHolder extends RecyclerView.ViewHolder {
        ...

        public MyViewHolder(View view) {
            super(view);
            ButterKnife.bind(this, view);

            section_title.setGravity(Gravity.RIGHT);
        }
    }

    public class MonthLessonsList extends RecyclerView.Adapter<MonthLessonsList.LessonsViewHolder> {
        private List<SectionLesson> lessonItem;

        public class LessonsViewHolder extends RecyclerView.ViewHolder {
            public TextView title;

            public LessonsViewHolder(View view) {
                super(view);
                title = view.findViewById(R.id.title);
            }
        }

        public MonthLessonsList(List<SectionLesson> lists) {
            this.lessonItem = lists;
        }

        @Override
        public LessonsViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
            View itemView = LayoutInflater.from(parent.getContext())
                    .inflate(R.layout.child_list_row, parent, false);

            return new LessonsViewHolder(itemView);
        }

        @SuppressLint("SetTextI18n")
        @Override
        public void onBindViewHolder(@NonNull LessonsViewHolder holder, int position) {
            SectionLesson lesson = lessonItem.get(position);
            holder.title.setText("درس: " + (position + 1) + ") " + lesson.getTitle());
        }

        @Override
        public int getItemCount() {
            return lessonItem.size();
        }
    }

}

Answer 1

Declare child adapter inside onBindViewHolder , and remove from global level. And no need to notify child adapter. Because that will be automatically filled when parent onBindViewHolder is called. Like

MonthLessonsList lessonsListAdapter = new MonthLessonsList(lessonsList);
holder.userChildCategories.setAdapter(lessonsListAdapter);