片段中的可展开列表视图出错

Question

所以我设置了我的ExpandableListView，我的TextView上有一个NullPointer 不应该返回"null"。

这是我的代码：

public class HelpFragment extends Fragment {
@BindView(R.id.expandableListView)
ExpandableListView expandableListView;
public static HelpFragment newInstance() {
HelpFragment fragment = new HelpFragment();
return fragment;
}
ExpandableListAdapter listAdapter;
List<String> listDataHeader;
HashMap<String, List<String>> listDataChild;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_help, null);
ButterKnife.bind(this, rootView);
prepareListData();
listAdapter = new ExpandableListAdapter(listDataHeader, listDataChild);
expandableListView.setAdapter(listAdapter);
Log.i("groups", listDataHeader.toString());
Log.i("details", listDataChild.toString());
return rootView;
}
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 Despicable Me TurboGrown Ups 2 Red 2 the Wolverine The Conjuring Despicable Me TurboGrown Ups 2 Red 2 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);
}
public class ExpandableListAdapter extends BaseExpandableListAdapter {
private List<String> _listDataHeader; // header titles
// child data in format of header title, child title
private HashMap<String, List<String>> _listDataChild;
public ExpandableListAdapter(List<String> listDataHeader,
HashMap<String, List<String>> listChildData) {
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) {
convertView = LayoutInflater.from(getActivity()).inflate(R.layout.list_item, null);
}
TextView txtListChild = (TextView) convertView.findViewById(R.id.expandedListItem);
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) {
convertView = LayoutInflater.from(getActivity()).inflate(R.layout.expandable_list_group, null);
}
TextView lblListHeader = (TextView) convertView.findViewById(R.id.listExpandableTitle);
lblListHeader.setText(headerTitle);
return convertView;
}
@Override
public boolean hasStableIds() {
return false;
}
@Override
public boolean isChildSelectable(int groupPosition, int childPosition) {
return true;
}
}

并且有错误：

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference

对于这一行：

txtListChild.setText(childText);

在getChildView方法中。

所以我不明白为什么它会为我返回 txtListChild 的空值。

我怀疑convertView为空，但这是不可能的，因为我涵盖了这种情况。所以也许我在隐蔽视图上做错了什么，因为它在片段中。

我真的被困住了。提前感谢！

编辑：我没有精确，但是当我单击一个项目时，空指针会出现

Answer 1

试试这种方式

if (convertView == null) {
LayoutInflater layoutInflater = (LayoutInflater) this.context
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = layoutInflater.inflate(R.layout. expandable_list_item, null);
}