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我有一個RSS feed，這時候我已經改變了原料來源是一個錯誤崩潰：RSS飼料 - 空對象引用
Attempt to invoke virtual method 'int java.util.ArrayList.size()' on a null object reference.
我已經通過我的新的鏈接，並看着我它應該仍然工作的邏輯（所有節點幾乎都是相同的），但由於某種原因它不。
理想情況下，我想同時使用這兩個鏈接。這是我的代碼可能的，因爲我以前一起使用過兩個鏈接。
任何想法爲什麼這不起作用？
新的鏈接（即我試圖使用）：https://feeds.finance.yahoo.com/rss/2.0/headline?s=yhoo,msft,tivo®ion=US&lang=en-US
舊鏈接：https://www.bloomberg.com/politics/feeds/site.xml
RSSFeed.java：
public class ReadRss extends AsyncTask<Void,Void,Void>{
ArrayList<FeedItem>feedItems;
RecyclerView recyclerView;
Context context;
static ArrayList<String>address;
static {
address=new ArrayList<>();
address.add("http://finance.yahoo.com/rss/headline?s=yhoo,msft,tivo");
//address.add("https://www.bloomberg.com/politics/feeds/site.xml");
//address.add("https://www.bloomberg.com/feeds/podcasts/etf_report.xml");
}
ProgressDialog progressDialog;
URL url;
public ReadRss(Context context, RecyclerView recyclerView){
this.recyclerView=recyclerView;
this.context=context;
progressDialog=new ProgressDialog(context);
progressDialog.setMessage("Loading...");
}
@Override
protected void onPreExecute() {
progressDialog.show();
super.onPreExecute();
}
@Override
protected void onPostExecute(Void aVoid) {
super.onPostExecute(aVoid);
progressDialog.dismiss();
MyAdapter adapter=new MyAdapter(context,feedItems);
recyclerView.setLayoutManager(new LinearLayoutManager(context));
recyclerView.addItemDecoration(new VerticalSpace(50));
recyclerView.setAdapter(adapter);
}
@Override
protected Void doInBackground(Void... params) {
ProcessXml(Getdata());
return null;
}
private void ProcessXml(ArrayList<Document> data) {
if (data != null) {
feedItems = new ArrayList<>();
for (Document doc : data) {
Element root = doc.getDocumentElement();
Node channel = root.getChildNodes().item(0);
NodeList items = channel.getChildNodes();
for (int i = 0; i < items.getLength(); i++) {
Node currentchild = items.item(i);
if (currentchild.getNodeName().equalsIgnoreCase("item")) {
FeedItem item = new FeedItem();
NodeList itemchilds = currentchild.getChildNodes();
for (int j = 0; j < itemchilds.getLength(); j++) {
Node current = itemchilds.item(j);
if (current.getNodeName().equalsIgnoreCase("title")) {
item.setTitle(current.getTextContent());
} else if (current.getNodeName().equalsIgnoreCase("description")) {
item.setDescription(current.getTextContent());
} else if (current.getNodeName().equalsIgnoreCase("pubDate")) {
item.setPubDate(current.getTextContent());
} else if (current.getNodeName().equalsIgnoreCase("link")) {
item.setLink(current.getTextContent());
}
}
feedItems.add(item);
Log.d("itemTitle", item.getTitle());
Log.d("itemDescription", item.getTitle());
Log.d("itemLink", item.getTitle());
Log.d("itemPubDate", item.getTitle());
}
}
}
}
}
public ArrayList<Document> Getdata(){
ArrayList<Document> documents = new ArrayList<>();
for (String addr: address) {
try {
url = new URL(addr);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("GET");
InputStream inputStream = connection.getInputStream();
DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = builderFactory.newDocumentBuilder();
Document xmlDoc = builder.parse(inputStream);
documents.add(xmlDoc);
} catch (Exception e) {
e.printStackTrace();
return null;
}
}
return documents;
}
}
MyAdapter。 java：
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder>{
ArrayList<FeedItem>feedItems;
Context context;
public MyAdapter(Context context,ArrayList<FeedItem>afeedItems){
this.feedItems= new ArrayList<FeedItem>(afeedItems);
this.context=context;
}
@Override
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view= LayoutInflater.from(context).inflate(R.layout.custum_row_news_item,parent,false);
MyViewHolder holder=new MyViewHolder(view);
return holder;
}
@Override
public void onBindViewHolder(MyViewHolder holder, int position) {
YoYo.with(Techniques.FadeIn).playOn(holder.cardView);
final FeedItem current=feedItems.get(position);
holder.Title.setText(current.getTitle());
holder.Description.setText(current.getDescription());
holder.Date.setText(current.getPubDate());
holder.cardView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(context, NewsDetails.class);
intent.putExtra("Link", current.getLink());
context.startActivity(intent);
}
});
}
@Override
public int getItemCount() {
return feedItems.size();
}
public class MyViewHolder extends RecyclerView.ViewHolder {
TextView Title,Description,Date;
CardView cardView;
public MyViewHolder(View itemView) {
super(itemView);
Title= (TextView) itemView.findViewById(R.id.title_text);
Description=(TextView) itemView.findViewById(R.id.description_text);
Date=(TextView) itemView.findViewById(R.id.date_text);
cardView= (CardView) itemView.findViewById(R.id.cardview);
}
}
}
@JoeC我做了我的研究之前，問題的解決方案沒有解決我的公關oblem。乾杯。 – Joe
擺脫NPE的解決方案是**始終**在實例化之前查找您正在使用的對象。 –
我試着做那個答案的建議，沒有運氣@Rotwang。這就是我問這個問題的原因。 – Joe