Android 列表返回空值
我正在制作一个android studio应用程序,它有一个选项卡,其中一个选项卡有一个rss提要,我试图将文章的标题和描述从添加到列表视图,但我得到一个例外:Android 列表返回空值,android,android-studio,rss,Android,Android Studio,Rss,我正在制作一个android studio应用程序,它有一个选项卡,其中一个选项卡有一个rss提要,我试图将文章的标题和描述从添加到列表视图,但我得到一个例外: java.lang.NullPointerException: Attempt to invoke interface method 'int java.util.List.size()' on a null object reference at android.widget.ArrayAdapter.getC
java.lang.NullPointerException: Attempt to invoke interface method 'int java.util.List.size()' on a null object reference
at android.widget.ArrayAdapter.getCount(ArrayAdapter.java:330)
at android.widget.ListView.setAdapter(ListView.java:487)
at com.example.pauly.myapplication.Tabs.Tab_1$GetRssFeed.onPostExecute(Tab_1.java:65)
at com.example.pauly.myapplication.Tabs.Tab_1$GetRssFeed.onPostExecute(Tab_1.java:45)
at android.os.AsyncTask.finish(AsyncTask.java:636)
at android.os.AsyncTask.access$500(AsyncTask.java:177)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:653)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5257)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Tab_1.java:
public class Tab_1 extends Fragment {
ListView mList;
ArrayList<Info> arrayOfInfo;
int i=0;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.tab_1, container, false);
mList = (ListView) v.findViewById(R.id.list);
new GetRssFeed().execute("http://feeds.bbci.co.uk/news/rss.xml");
return v;
}
l.45- private class GetRssFeed extends AsyncTask<String, Void, Void> {
@Override
protected Void doInBackground(String... params) {
try {
RssReader rssReader = new RssReader(params[0]);
for (RssItem item : rssReader.getItems()) {
arrayOfInfo.add(i++, new Info(item.getTitle(), item.getDescription()));
}
} catch (Exception e) {
Log.v("Error Parsing Data", e + "");
}
return null;
}
@Override
protected void onPostExecute(Void aVoid) {
super.onPostExecute(aVoid);
LAdapter adapter = new LAdapter(getActivity(), arrayOfInfo);
adapter.notifyDataSetChanged();
l.65 mList.setAdapter(adapter);
}
}
}
公共类选项卡\u 1扩展了片段{
ListView-mList;
ArrayList arrayOfInfo;
int i=0;
@凌驾
创建时的公共void(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
}
@凌驾
CreateView上的公共视图(布局、充气机、视图组容器、捆绑包保存状态){
视图v=充气机。充气(R.layout.tab_1,容器,错误);
mList=(ListView)v.findViewById(R.id.list);
新建GetRssFeed()。执行(“http://feeds.bbci.co.uk/news/rss.xml");
返回v;
}
l、 45-私有类GetRssFeed扩展异步任务{
@凌驾
受保护的Void doInBackground(字符串…参数){
试一试{
RssReader RssReader=新RssReader(参数[0]);
对于(RssItem项:rssReader.getItems()){
添加(i++,新信息(item.getTitle(),item.getDescription());
}
}捕获(例外e){
Log.v(“分析数据时出错”,e+);
}
返回null;
}
@凌驾
受保护的void onPostExecute(void避免){
super.onPostExecute(避免);
LAdapter adapter=新的LAdapter(getActivity(),arrayOfInfo);
adapter.notifyDataSetChanged();
l、 65 mList.setAdapter(适配器);
}
}
}
您需要分配ArrayList对象
ArrayList<Info> arrayOfInfo;
arraylistarrayofinfo;
取代
ArrayList<Info> arrayOfInfo=new ArrayList<>();
ArrayList arrayOfInfo=new ArrayList();