ExpandableListView shows nothing

Question

No errors, no warnings, it compiles successfully, but my ExpandableListView is not showing anything. Here is my ExpandableListViewAdapter class:

public class ExpandableListAdapter extends BaseExpandableListAdapter {


private Context _context;
private List<String> _listDataHeader; // header titles
// child data in format of header title, child title
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;
}


}

Here is my ListViewtest class:

public class ListViewTest extends AppCompatActivity {

ExpandableListAdapter listAdapter;
ExpandableListView expListView;
List<String> listDataHeader;
HashMap<String, List<String>> listDataChild;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);


    // get the listview
   // expListView = (ExpandableListView) findViewById(R.id.lvExp);
    View explist = getLayoutInflater().inflate(R.layout.activity_expandable_list,null,false );
    expListView = (ExpandableListView) explist.findViewById(R.id.lvExp);
    // preparing list data
    prepareListData();

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



    // setting list adapter
    expListView.setAdapter(listAdapter);
    setContentView(R.layout.activity_expandable_list);

}

/*
 * Preparing the list data
 */
private void prepareListData() {
    listDataHeader = new ArrayList<String>();
    listDataChild = new HashMap<String, List<String>>();

    // Adding child data
    listDataHeader.add("Top 250");
    listDataHeader.add("Now Showing");
    listDataHeader.add("Coming Soon..");

    // Adding child data
    List<String> top250 = new ArrayList<String>();
    top250.add("The Shawshank Redemption");
    top250.add("The Godfather");
    top250.add("The Godfather: Part II");
    top250.add("Pulp Fiction");
    top250.add("The Good, the Bad and the Ugly");
    top250.add("The Dark Knight");
    top250.add("12 Angry Men");

    List<String> nowShowing = new ArrayList<String>();
    nowShowing.add("The Conjuring");
    nowShowing.add("Despicable Me 2");
    nowShowing.add("Turbo");
    nowShowing.add("Grown Ups 2");
    nowShowing.add("Red 2");
    nowShowing.add("The Wolverine");

    List<String> comingSoon = new ArrayList<String>();
    comingSoon.add("2 Guns");
    comingSoon.add("The Smurfs 2");
    comingSoon.add("The Spectacular Now");
    comingSoon.add("The Canyons");
    comingSoon.add("Europa Report");

    listDataChild.put(listDataHeader.get(0), top250); // Header, Child data
    listDataChild.put(listDataHeader.get(1), nowShowing);
    listDataChild.put(listDataHeader.get(2), comingSoon);
}

I don't know what I am doing wrong. Can anyonone tell me where the problem my be ? Thank you in advance.

Answer 1

Focus on following code:

setContentView(R.layout.activity_expandable_list);

Here R.layout.activity_expandable_list is just an int. so you need to set to view object. Try:

View root = binding.getRoot();
setContentView(root);

Answer 2

You override all layout changes by calling this:

setContentView(R.layout.activity_expandable_list);

This might fix the problem:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_expandable_list);

    // get the listview
    expListView = (ExpandableListView) findViewById(R.id.lvExp);
    // preparing list data
    prepareListData();

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



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