我尝试使用jsoup和朋友网站的内容在片段中填充我的自定义列表视图，但每当我打开该片段时我的应用程序崩溃，这里是我使用的代码 公共类FragmentPoems扩展Fragment {
ListView listview;
ListViewAdapter adapter;
ProgressDialog mProgressDialog;
ArrayList<HashMap<String, String>> arraylist;
static String TITLE = "title";
static String DESCRIPTION = "description";
String url = "http://www.writenepal.com/archives/category/poems";
public FragmentPoems() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_poems, container, false);
TextView textView = (TextView) view.findViewById(R.id.text_category);
textView.setText("Poems");
new JsoupListView().execute();
// Locate the listview in listview_main.xml
listview = (ListView) view.findViewById(R.id.my_list_view);
// Pass the results into ListViewAdapter.java
adapter = new ListViewAdapter(getActivity(), arraylist);
// Set the adapter to the ListView
listview.setAdapter(adapter);
return view;
}
private class JsoupListView extends AsyncTask<Void, Void, Void> {
@Override
protected void onPreExecute() {
super.onPreExecute();
// Create a progressdialog
mProgressDialog = new ProgressDialog(getContext());
// Set progressdialog title
mProgressDialog.setTitle("Write Nepal");
// Set progressdialog message
mProgressDialog.setMessage("Loading...");
mProgressDialog.setIndeterminate(false);
// Show progressdialog
mProgressDialog.show();
}
@Override
protected Void doInBackground(Void... params) {
arraylist = new ArrayList<HashMap<String, String>>();
try {
// Connect to the Website URL
/* Document doc = Jsoup.connect(url).get();
// Identify Table Class "worldpopulation"
for (Element table : doc.select("table[class=worldpopulation]")) {
// Identify all the table row's(tr)
for (Element row : table.select("tr:gt(0)")) {
HashMap<String, String> map = new HashMap<String, String>();
// Identify all the table cell's(td)
Elements tds = row.select("td");
// Identify all img src's
Elements imgSrc = row.select("img[src]");
// Get only src from img src
String imgSrcStr = imgSrc.attr("src");
// Retrive Jsoup Elements
// Get the first td
map.put("rank", tds.get(0).text());
// Get the second td
map.put("country", tds.get(1).text());
// Get the third td
map.put("population", tds.get(2).text());
// Get the image src links
map.put("flag", imgSrcStr);
// Set all extracted Jsoup Elements into the array
*/
Document doc = Jsoup.connect(url).get();
Elements titles = doc.select("div.span8 h2");
Elements descriptions = doc.select("div.readmore.archive-inbox i");
int l = titles.size();
for (int i = 0; i < l; i++) {
HashMap<String, String> map = new HashMap<String, String>();
map.put("title", titles.get(0).text());
map.put("description", descriptions.get(1).text());
arraylist.add(map);
//String tit=titles.get(i).text();
//String des=descriptions.get(i).text();
//data.add(new Contents(tit,des));
}
//arraylist.add(map);
} catch (IOException e1) {
e1.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(Void result) {
// Close the progressdialog
mProgressDialog.dismiss();
}
}
package com.bct071.myapplication;
公共类ListViewAdapter扩展了BaseAdapter {
// Declare Variables
Context context;
LayoutInflater inflater;
ArrayList<HashMap<String, String>> data;
HashMap<String, String> resultp = new HashMap<String, String>();
public ListViewAdapter(Context context,
ArrayList<HashMap<String, String>> arraylist) {
this.context = context;
data = arraylist;
}
@Override
public int getCount() {
return data.size();
}
@Override
public Object getItem(int position) {
return null;
}
@Override
public long getItemId(int position) {
return 0;
}
public View getView(final int position, View convertView, ViewGroup parent) {
// Declare Variables
TextView title;
TextView description;
//TextView population;
inflater = (LayoutInflater) context
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View itemView = inflater.inflate(R.layout.abc_show_titles, parent, false);
// Get the position
resultp = data.get(position);
// Locate the TextViews in listview_item.xml
title = (TextView) itemView.findViewById(R.id.text_title);
description = (TextView) itemView.findViewById(R.id.text_description);
//population = (TextView) itemView.findViewById(R.id.population);
// Locate the ImageView in listview_item.xml
// flag = (ImageView) itemView.findViewById(R.id.flag);
// Capture position and set results to the TextViews
title.setText(resultp.get(FragmentPoems.TITLE));
description.setText(resultp.get(FragmentPoems.DESCRIPTION));
//population.setText(resultp.get(MainActivity.POPULATION));
// Capture position and set results to the ImageView
// Passes flag images URL into ImageLoader.class
//imageLoader.DisplayImage(resultp.get(MainActivity.FLAG), flag);
// Capture ListView item click
/*
itemView.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
// Get the position
resultp = data.get(position);
Intent intent = new Intent(context, SingleItemView.class);
// Pass all data rank
intent.putExtra("rank", resultp.get(MainActivity.RANK));
// Pass all data country
intent.putExtra("country", resultp.get(MainActivity.COUNTRY));
// Pass all data population
intent.putExtra("population",resultp.get(MainActivity.POPULATION));
// Pass all data flag
intent.putExtra("flag", resultp.get(MainActivity.FLAG));
// Start SingleItemView Class
context.startActivity(intent);
}
});
*/
return itemView;
}
}
这是我得到的错误
Process: com.bct071.myapplication, PID: 22075
java.lang.NullPointerException: Attempt to invoke virtual method 'int java.util.ArrayList.size()' on a null object reference
at com.bct071.myapplication.ListViewAdapter.getCount(ListViewAdapter.java:37)
at android.widget.ListView.setAdapter(ListView.java:491)
at com.bct071.myapplication.FragmentPoems.onCreateView(FragmentPoems.java:62)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:1974)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1067)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1252)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:742)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1617)
at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:517)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
05-28 13：55：37.050 1619-1633 / system_process W / ActivityManager：强制完成活动com.bct071.myapplication / .MainActivity
答案 0 :(得分：0)
尝试初始化arraylist ..
ArrayList<HashMap<String, String>> data=new ArrayList<Hashmap<String,String>>();
或
ArrayList<HashMap<String, String>> data=null;