Question

我是NavigationDrawer中ExpandableListView的新手。我的问题是，所有具有子菜单的标题菜单正在扩展和正确折叠，但那些没有任何子菜单的标题菜单会使我的应用程序崩溃并出现NullPointerException。这是我的代码

listDataHeader.add("Home");
listDataHeader.add("Bhopal");
listDataHeader.add("Indore");
listDataHeader.add("Jaipur");
listDataHeader.add("Udaipur");
listDataHeader.add("Ajmer");
listDataHeader.add("Jodhpur");
listDataHeader.add("Chandigarh");
listDataHeader.add("Lakhnow");

// Adding child data
List<String> bhopal_ = new ArrayList<String>();
bhopal_.add("About Us");
bhopal_.add("Board Members");
bhopal_.add("Chaiman Messages");

List<String> indore_ = new ArrayList<String>();
indore_.add("Heritage of Indore");
indore_.add("City Map");

List<String> udaipur_ = new ArrayList<String>();
udaipur_.add("Live");
udaipur_.add("Old");

List<String> lakhnow_ = new ArrayList<String>();
lakhnow_.add("Procurement");
lakhnow_.add("Schemes");
lakhnow_.add("Auctions");

listDataChild.put(listDataHeader.get(1), bhopal_); // Header, Child data
listDataChild.put(listDataHeader.get(2), indore_);
listDataChild.put(listDataHeader.get(4), udaipur_);
listDataChild.put(listDataHeader.get(8), lakhnow_);

这是我的适配器代码

public class ExpandableListAdapter extends BaseExpandableListAdapter {

    Context mContext;
    List<String> listDataHeader;
    HashMap<String, List<String>> listDataChild;

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

    @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 int getChildrenCount(int groupPosition) {
        return listDataChild.get(listDataHeader.get(groupPosition)).size();
    }

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

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

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

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

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

        TextView tv_head_txt = (TextView) convertView.findViewById(R.id.lblListHeader);
        tv_head_txt.setText(header_title);
        tv_head_txt.setTypeface(Utilities.myFont(mContext));

        return convertView;
    }

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

        final String child_title = String.valueOf(getChild(groupPosition, childPosition));
        if (convertView == null) {
            LayoutInflater infalInflater = (LayoutInflater) this.mContext
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = infalInflater.inflate(R.layout.menu_list_item, null);
        }

        TextView tv_head_txt = (TextView) convertView.findViewById(R.id.lblListItem);
        tv_head_txt.setText(child_title);
        tv_head_txt.setTypeface(Utilities.myFont(mContext));

        return convertView;
    }

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

在特定标题菜单中没有子菜单时会出现异常。

Answer 1

您的 groupPosition 即将 null ，这就是它崩溃的原因。你可以在下面的代码中试试这个。

@Override
    public int getChildrenCount(int groupPosition) {
      int pos =0;
    if(groupPosition != null){
          if( (listDataHeader.get(groupPosition)!= null) && (listDataChild.get(listDataHeader.get(groupPosition)).size() != null)){
           pos  =  listDataChild.get(listDataHeader.get(groupPosition)).size();
        }else{ 
          pos =0;
        } 
    }
    return pos;
    }

Answer 2

您只需按如下方式初始化列表，

 listDataChild.put(listDataHeader.get(3), new ArrayList<String>());
 listDataChild.put(listDataHeader.get(5), new ArrayList<String>());
 listDataChild.put(listDataHeader.get(6), new ArrayList<String>());
 listDataChild.put(listDataHeader.get(7), new ArrayList<String>());

可以解决您的问题

Answer 3

将其设为0。

 @Override
public int getChildrenCount(int i) {
    return listDataChild.get(listDataHeader.get(i)).size()>0?listDataChild.get(listDataHeader.get(i)).size():0;
}

如何制作没有子项的可扩展ListView

3 个答案: