public class ExpandableListAdapter extends BaseExpandableListAdapter {

    private Context _context;
    private List<String> _listDataHeader ;
    private HashMap<String, List<String>> _listDataChild;

    public ExpandableListAdapter(Context context, List<String> listDataHeader,
                                 HashMap<String, List<String>> listChildData) {
        this._context = context;
        this._listDataHeader = listDataHeader;
        this._listDataChild = listChildData;
    }

    @Override
    public Object getChild(int groupPosition, int childPosititon) {
        return this._listDataChild.get(this._listDataHeader.get(groupPosition))
                .get(childPosititon);
    }

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

    @Override
    public View getChildView(int groupPosition, final int childPosition,
                             boolean isLastChild, View convertView, ViewGroup parent) {

        final String childText = (String) getChild(groupPosition, childPosition);

        if (convertView == null) {
            LayoutInflater infalInflater = (LayoutInflater) this._context
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = infalInflater.inflate(R.layout.list_item, null);
        }

        TextView txtListChild = (TextView) convertView
                .findViewById(R.id.lblListItem);

        txtListChild.setText(childText);
        return convertView;
    }

    @Override
    public int getChildrenCount(int groupPosition) {
        return this._listDataChild.get(this._listDataHeader.get(groupPosition))
                .size();
    }

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

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

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

    @Override
    public View getGroupView(int groupPosition, boolean isExpanded,
                             View convertView, ViewGroup parent) {
        String headerTitle = (String) getGroup(groupPosition);
        if (convertView == null) {
            LayoutInflater infalInflater = (LayoutInflater) this._context
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = infalInflater.inflate(R.layout.list_group, null);
        }

        TextView lblListHeader = (TextView) convertView
                .findViewById(R.id.lblListHeader);
        lblListHeader.setTypeface(null, Typeface.BOLD);
        lblListHeader.setText(headerTitle);

        return convertView;
    }

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

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

public class MainActivityFragment extends Fragment {

//Expandable list Adapter
    ExpandableListAdapter listAdapter;
    ExpandableListView expListView;
    List<String> listDataHeader;
    HashMap<String, List<String>> listDataChild;

    //Users
    private List <User> items = new ArrayList<>();

    //Obejeto a pasar
    User user = new User();
    String password;

 @Override
    public View onCreateView(LayoutInflater inflater, final ViewGroup container,
                             Bundle savedInstanceState) {
        view = inflater.inflate(R.layout.fragment_main, container, false);

        //Botones
        TextPass = (EditText) view.findViewById(R.id.IdpasswordUser);
        TextName = (TextView) view.findViewById(R.id.text1);

        // get the listview
        expListView = (ExpandableListView) view.findViewById(R.id.lvExp);

        // preparing list data
        prepareListData();

        listAdapter = new ExpandableListAdapter(getActivity(), listDataHeader, listDataChild);

        // setting list adapter
        expListView.setAdapter(listAdapter);

        ExpandableListView ExList =(ExpandableListView) view.findViewById(R.id.lvExp) ;



                //Llamamos al boton fichar
        fichar = (Button) view.findViewById(R.id.fichar);

//Call ExpandibleList view child on pressed

        ExList.setOnChildClickListener(new ExpandableListView.OnChildClickListener() {

            @Override
            public boolean onChildClick(ExpandableListView parent, View v,
                                        int groupPosition, int childPosition, long id) {

                 ShowItem(listDataHeader.get(childPosition));

                TextName.setText(listAdapter.getChild(groupPosition,childPosition).toString());

                return false;
            }
        });

        fichar.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                password = TextPass.getText().toString();
                //SuperUsuario
                if(key.equalsIgnoreCase("cesi.tic")&&password.equalsIgnoreCase("123456789")){
                    ((MainActivity) getActivity()).EditarUsuario();
                    fichar.setVisibility(view.INVISIBLE);
                    TextPass.setVisibility(view.INVISIBLE);
                    TextDNI.setVisibility(view.INVISIBLE);
                }else{
                    LeerFirebase();
                }

            }
        });
        return view;
    }
    public void ShowItem(String id)
    {
        // do something
    }
}