Question

我正在使用RecyclerView来显示来自各个RSS网站的RSS供稿。当应用加载且设备离线时，应用崩溃并显示以下错误

 at com.nepalpolice.sample.alarm.data.Adapter.FeedAdapter.getItemCount(FeedAdapter.java:104)

但是，如果应用程序处于在线状态，则应用程序会顺利加载，并且下次设备脱机时，应用程序也会正常运行。但是只有当应用首次加载且设备离线时，才有应用崩溃。...当我单击日志错误时....它会将我定向到以下行

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

这是整个类的代码

class FeedViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener,View.OnLongClickListener
{

    public TextView txtTitle,txtPubDate,txtContent;
    private ItemClickListener itemClickListener;




    public FeedViewHolder(View itemView) {
        super(itemView);

        txtTitle = (TextView)itemView.findViewById(R.id.txtTitle);
        txtPubDate = (TextView)itemView.findViewById(R.id.txtPubDate);
        txtContent = (TextView)itemView.findViewById(R.id.txtContent);

        //Set Event
        itemView.setOnClickListener(this);
        itemView.setOnLongClickListener(this);
    }

    public void setItemClickListener(ItemClickListener itemClickListener) {
        this.itemClickListener = itemClickListener;
    }

    @Override
    public void onClick(View v) {

        itemClickListener.onClick(v,getAdapterPosition(),false);

    }

    @Override
    public boolean onLongClick(View v) {
        itemClickListener.onClick(v,getAdapterPosition(),true);
        return true;
    }
}

public class FeedAdapter extends RecyclerView.Adapter<FeedViewHolder> {

    private RSSObject rssObject;
    private Context mContext;
    private LayoutInflater inflater;

    public FeedAdapter(RSSObject rssObject, Context mContext) {
        this.rssObject = rssObject;
        this.mContext = mContext;
        inflater = LayoutInflater.from(mContext);
    }

    @Override
    public FeedViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
       View itemView = inflater.inflate(R.layout.row,parent,false);
        return new FeedViewHolder(itemView);
    }

    @Override
    public void onBindViewHolder(FeedViewHolder holder, int position) {

        holder.txtTitle.setText(rssObject.getItems().get(position).getTitle());
        holder.txtPubDate.setText(rssObject.getItems().get(position).getPubDate());
        holder.txtContent.setText(rssObject.getItems().get(position).getContent());

        holder.setItemClickListener(new ItemClickListener() {
            @Override
            public void onClick(View view, int position, boolean isLongClick) {
                if(!isLongClick)
                {





                    Intent browserIntent = new Intent(Intent.ACTION_VIEW, Uri.parse(rssObject.getItems().get(position).getLink()));
                    browserIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

                    mContext.startActivity(browserIntent);
                }
            }
        });

    }

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

这是主要的片段代码

public class Movie extends Fragment {

    RecyclerView recyclerView;
    RSSObject rssObject;


    private final String RSS_link="http://www.bollywoodhungama.com/rss/movie-release-date.xml";
    private final String RSS_to_Json_API = "https://api.rss2json.com/v1/api.json?rss_url=";

    public Movie() {
        // Required empty public constructor
    }


    @Override
    public View onCreateView(LayoutInflater inflater, final ViewGroup container,
                             Bundle savedInstanceState) {

        View view = inflater.inflate(R.layout.activity_mainrss, container, false);

        recyclerView = (RecyclerView)view.findViewById(R.id.recyclerView);
        LinearLayoutManager linearLayoutManager  = new LinearLayoutManager(getActivity().getBaseContext(),LinearLayoutManager.VERTICAL,false);
        recyclerView.setLayoutManager(linearLayoutManager);
        loadRSS();



        return view;
    }

    private void loadRSS() {
        AsyncTask<String,String,String> loadRSSAsync = new AsyncTask<String, String, String>() {

            ProgressDialog mDialog = new ProgressDialog(getActivity());

            @Override
            protected void onPreExecute() {
                mDialog.setMessage("Please wait...");
                mDialog.show();
            }

            @Override
            protected String doInBackground(String... params) {
                String result;
                HTTPDataHandler http = new HTTPDataHandler();
                result = http.GetHTTPData(params[0]);
                return  result;
            }

            @Override
            protected void onPostExecute(String s) {
                mDialog.dismiss();
                rssObject = new Gson().fromJson(s,RSSObject.class);
                FeedAdapter adapter = new FeedAdapter(rssObject,getActivity().getBaseContext());
                recyclerView.setAdapter(adapter);
                adapter.notifyDataSetChanged();
            }
        };

        StringBuilder url_get_data = new StringBuilder(RSS_to_Json_API);
        url_get_data.append(RSS_link);
        loadRSSAsync.execute(url_get_data.toString());
    }

    }

任何人都可以帮助我解决此错误以及如何解决此问题吗？

Answer 1

好像您正在创建RSSObject的对象，但是其中的列表将被初始化为null，以避免这种使用

@Override
public int getItemCount() {
    return (rssObject!=null && rssObject.items!=null)? rssObject.items.size():0;
// if object and list is not null then return size otherwise return 0
}

Answer 2

显示rssObject是否为空：

@Override
public int getItemCount() {
    if (rssObject == null) {
         Toast.makeText(context, "rssObject is NUll", Toast.LENGTH_SHORT).show();
         return 0;
    }
    else {
    return (rssObject!=null && rssObject.items!=null)? rssObject.items.size():0;
    }
}

尝试一下是否有效。

Answer 3

@Override
public int getItemCount() {
    if (rssObject == null) {
        Toast.makeText(context, "rssObject is NUll", Toast.LENGTH_SHORT).show();
        return 0;
    } else {
        return (rssObject != null && rssObject.items != null) ?
               rssObject.items.size() : 0;
    }
}

当我的应用程序首次加载时，在RecyclerView中摆脱了空指针异常

3 个答案: