notifyDataSetChanged not working in custom BaseExpandableListAdapter

Question

My navigation drawer has an ExpandableListView and I want to update its content at runtime. Everything is working as expected, except notifyDataSetChanged. When I call notifyDataSetChanged in my custom ExpandableListAdapter. I've already tried all the workarounds present on the internet but nothing seems to be working. Here's my adapter

public class ExpandableListAdapter extends BaseExpandableListAdapter {

private Context mContext;
private List<String> mListGroup;
private HashMap<String, List<String>> mListChild;

public ExpandableListAdapter(Context mContext, List<String> mListGroup, HashMap<String, List<String>> mListChild) {
    this.mContext = mContext;
    this.mListGroup = mListGroup;
    this.mListChild = mListChild;
}

@Override
public int getGroupCount() {
    return mListGroup.size();
}

@Override
public int getChildrenCount(int groupPosition) {
    return mListChild.get(mListGroup.get(groupPosition)).size();
}

@Override
public Object getGroup(int groupPosition) {
    return mListGroup.get(groupPosition);
}

@Override
public Object getChild(int groupPosition, int childPosition) {
    return mListChild.get(mListGroup.get(groupPosition)).get(childPosition);
}

@Override
public long getGroupId(int groupPosition) {
    return groupPosition;
}

@Override
public long getChildId(int groupPosition, int childPosition) {
    return childPosition;
}

@Override
public View getGroupView(int groupPosition, boolean isExpanded, View convertView,
                         ViewGroup parent) {
    String groupTitle = (String) getGroup(groupPosition);
    if (convertView == null) {
        LayoutInflater inflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        convertView = inflater.inflate(R.layout.nav_list_group_main, null);
    }
    TextView title = convertView.findViewById(R.id.expandable_list_group_main);
    title.setTypeface(null, Typeface.BOLD);
    title.setText(groupTitle);

    return convertView;
}

@Override
public View getChildView(int groupPosition, int childPosition, boolean isLastChild,
                         View convertView, ViewGroup parent) {
    String childTitle = (String) getChild(groupPosition, childPosition);
    if (convertView == null) {
        LayoutInflater inflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        convertView = inflater.inflate(R.layout.nav_list_child_main, null);
    }
    TextView title = convertView.findViewById(R.id.expandable_list_child_main);
    title.setText(childTitle);

    return convertView;
}

@Override
public boolean hasStableIds() {
    return false;
}

@Override
public boolean isChildSelectable(int groupPosition, int childPosition) {
    return true;
}
}

And here's the snippet trying to update data.

 private void updatetNavigationMenu() {
    List<String> group = Arrays.asList("a", "b", "c", "d");
    List<String> child = Arrays.asList("1", "2", "3", "4");

    expandableListChild.put(group.get(0), child);
    expandableListChild.put(group.get(1), child);
    expandableListChild.put(group.get(2), child);
    expandableListChild.put(group.get(3), child);
    expandableListGroup = new ArrayList<>(expandableListChild.keySet());

    expandableListAdapter.notifyDataSetChanged();
}

After calling notifyDataSetChanged the mListGroup and mListChild does not change. I've tried clearing them manually but that doesn't work either. Thanks!

Answer 1

You need a setter method in your adapter like

void setData(List<String> list, HashMap<String, List<String>> child) {
    this.mListGroup = list;
    this.mListChild = child;
    notifyDataSetChanged();
}

And in the end of your updatetNavigationMenu call

expandableListAdapter.setData( group, expandableListGroup) ;

notifyDataSetChanged will tell the adapter to refresh.