Arraylist lançant l'exception Nullpointer dans les versions Android ci-dessous Marshmallow

Question

J'essaie d'utiliser RssReader en utilisant une bibliothèque feedparser. Il fonctionne bien sur Android M & N mais il se bloque sur les versions L et ci-dessous. ici est ce que je l'ai fait

ReadRss readRss = new ReadRss(this, recyclerView); 
     isNetworkAvailable(); 
     if (isNetworkAvailable()) { 
      readRss.execute(); 
     } else { 
      Toast.makeText(getBaseContext(), "Couldn't connect to Internet.", Toast.LENGTH_LONG).show(); 
     } 

ReadRss est la suivante

class ReadRss extends AsyncTask<Void, Void, Void> { 
Context context; 
private ProgressDialog progressDialog; 
private ArrayList<FeedItem> feedItems; 
private RecyclerView recyclerView; 

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(); 
    RssAdapter adapter = new RssAdapter(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(Document data) { 
    try { 
     URL url = new URL("http:pockettanksnews.blogspot.com/feeds/posts/default"); 
     HttpURLConnection httpConnection = (HttpURLConnection) url.openConnection(); 
     if (httpConnection.getResponseCode() == HttpURLConnection.HTTP_OK) { 
      InputStream feedStream = httpConnection.getInputStream(); 
      FeedParser parser = FeedParserFactory.newParser(); 
      System.out.println("success"); 
      Feed feed = parser.parse(feedStream); 
      feedItems=new ArrayList<>(); 
      for (Item i : feed.getItemList()) { 
       FeedItem item=new FeedItem(); 
       System.out.println(i.getTitle()); 
       item.setTitle(i.getTitle()); 
       System.out.println(i.getLink()); 
       item.setLink(i.getLink()); 
       System.out.println(i.getPubDate()); 
       item.setPubDate(i.getPubDate().toString()); 
       item.setThumbnailUrl("https:1079638729.rsc.cdn77.org/androidgame_img/pocket_tanks/real/1_pocket_tanks.jpg"); 
       item.setDescription(i.getDescription()); 
       feedItems.add(item); 
      } 

     } else { 
      System.out.println("error"); 
     } 
    } 
    catch (Exception except){ 
     ; 
    } 
} 

private Document Getdata() { 
    try { 
     String address = "http://pockettanksnews.blogspot.com/feeds/posts/default/-/pttipsyoutube/?alt=rss"; 
     URL url = new URL(address); 
     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); 
     return xmlDoc; 
    } catch (Exception e) { 
     e.printStackTrace(); 
     return null; 
    } 
} 

et mon RssAdapter est comme ci-dessous

public class RssAdapter extends RecyclerView.Adapter<RssAdapter.MyViewHolder> { 
ArrayList<FeedItem> feedItems=new ArrayList<FeedItem>(); 
Context context; 

public RssAdapter(Context context, ArrayList<FeedItem> feedItems) { 
    this.feedItems = feedItems; 
    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) { 
    FeedItem current = feedItems.get(position); 
    holder.Title.setText(current.getTitle()); 
    holder.Description.loadDataWithBaseURL("", current.getDescription(), "text/html", "UTF-8", ""); 
    holder.Date.setText(current.getPubDate()); 

} 

@Override 
public int getItemCount() { 
    return feedItems.size(); 
} 

public class MyViewHolder extends RecyclerView.ViewHolder { 
    TextView Title, Date; 
    WebView Description; 
    ImageView Thumbnail; 
    CardView cardView; 

    public MyViewHolder(View itemView) { 
     super(itemView); 
     Title = (TextView) itemView.findViewById(R.id.title_text); 
     Description = (WebView) itemView.findViewById(R.id.description_text); 
     Description.getSettings().setJavaScriptEnabled(true); 
     Date = (TextView) itemView.findViewById(R.id.date_text); 
     Thumbnail = (ImageView) itemView.findViewById(R.id.thumb_img); 
     cardView = (CardView) itemView.findViewById(R.id.cardview); 
    } 
} 

Les accidents d'application sur la méthode GetItemCount. Il affiche l'exception Pointeur nul: Tentative d'invocation de la méthode virtuelle 'int java.util.ArrayList.size()' sur une référence d'objet null.

Answer 1

En cas d'erreur, vos flux deviendront nuls. Alors changez votre code et manipulez le.

// Add null check here. 
if(feedItems!= null) { 
RssAdapter adapter = new RssAdapter(context, feedItems); 
recyclerView.setLayoutManager(new LinearLayoutManager(context)); 
recyclerView.addItemDecoration(new VerticalSpace(50)); 
recyclerView.setAdapter(adapter); 
} else { 
// Show some error 
} 

Une autre façon de gérer ce pointeur nul est d'ajouter une vérification null dans Adapter. Ensuite, essayez de trouver une exception dans l'obtention des données du serveur. Je crois que seule la méthode Getdata() est responsable de cela.