Listview设置适配器片段nullpointerexception
问题描述:
我目前有3个片段,但我无法让我的适配器工作。 当我调用lv.setAdapter(lbadapter)时,它返回一个空指针异常。 可能是什么问题?Listview设置适配器片段nullpointerexception
在此先感谢
这里是我的片段的一部分:
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView;
rootView = inflater.inflate(R.layout.leadlist, container, false);
profielen = new ArrayList<Profile>();
new getLeaderboards().execute(url);
lv = (ListView) this.getActivity().findViewById(android.R.id.list);
lbadapter = new LeaderBoardAdapter(this.getActivity(), R.layout.item_layout, profielen);
return rootView;
}
public static class getLeaderboards extends AsyncTask<String, Void, JsonObject> {
@Override
protected JsonObject doInBackground(String... urls) {
JsonObject x = parseURL.GetJSON(urls[0]);
return x;
}
@Override
protected void onPostExecute(JsonObject obj) {
Gson gson = new Gson();
JsonArray arr = obj.get("rows").getAsJsonArray();
for (JsonElement el : arr) {
Profile pat = gson.fromJson(el , Profile.class);
profielen.add(pat);
}
lv.setAdapter(lbadapter);
}
}
这是我的leadlist.xml文件:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<ListView
android:id="@android:id/list"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_centerInParent="true"
android:divider="@null"
android:dividerHeight="20dp" >
</ListView>
</RelativeLayout>
我的适配器:
public class LeaderBoardAdapter extends ArrayAdapter<Profile>{
LayoutInflater vi;
List<Profile> profielen;
Context mContext;
int res;
public LeaderBoardAdapter(Context context, int resource,
List<Profile> objects) {
super(context, resource, objects);
this.res = resource;
this.profielen = objects;
mContext = context;
vi = (LayoutInflater) context
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
// TODO Auto-generated method stub
ProfileHolder holder = null;
if(convertView == null)
{
LayoutInflater inflater = ((Activity)mContext).getLayoutInflater();
convertView = vi.inflate(R.layout.item_layout, parent, false);
convertView = inflater.inflate(res, parent, false);
holder = new ProfileHolder();
holder.name = (TextView)convertView.findViewById(R.id.nameChar);
holder.pic = (ImageView)convertView.findViewById(R.id.imageChar);
holder.rank = (TextView)convertView.findViewById(R.id.ratingNumber);
convertView.setTag(holder);
}
else
{
holder = (ProfileHolder)convertView.getTag();
}
Profile p = profielen.get(position);
holder.name.setText(p.getName());
holder.rank.setText(p.getRanking());
return convertView;
}
public static class ProfileHolder{
TextView name;
ImageView pic;
TextView rank;
}
}
答
lv = (ListView) this.getActivity().findViewById(android.R.id.list);
反而这样做。由于列表视图与您的Activity
没有直接关系。这是片段内封闭的视图,其持有的ListView
lv = (ListView) rootView.findViewById(android.R.id.list);
答
问题在于你初始化ListView的方式。如果您发现它属于您的leadlist.xml文件。但是在初始化你打电话,
lv = (ListView) this.getActivity().findViewById(android.R.id.list); // this means your listView lv belongs to your MainActivity which actually doesn't.
更改为,
lv = (ListView) rootView.findViewById(android.R.id.list);
,它应该工作。让我知道它是怎么回事。快乐编码:)
尝试初始化ListView后启动AsyncTask –
可以任何帮助http://*.com/questions/28148618/listview-not-refreshing-after-click-on-button – 2015-01-27 13:23:39