java - 在 recyclerView 中显示元素列表失败

Question

我正在尝试制作一个新闻应用程序，从 RSS feed 获取数据。我从提要中获取 xml 响应。我正在使用 XmlPullParser 来解析 xml。解析成功。我可以在日志中看到这些值。

但不知何故，我无法将它们填充到我的 recyclerView 中。一切都只是空白。我的java类是:

public class RssNewsActivity extends AppCompatActivity {
private static final String TAG = RssNewsActivity.class.toString();

RssFeedAdapter adapter;
RecyclerView recyclerView_rssFeed;
SwipeRefreshLayout swipeRefreshLayout;

private List<RssModel> listResponseModel;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_rss_news);

    initialize();

    recyclerView_rssFeed.setHasFixedSize(true);
    LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
    recyclerView_rssFeed.setLayoutManager(linearLayoutManager);

    adapter = new RssFeedAdapter(RssNewsActivity.this, listResponseModel);
    recyclerView_rssFeed.setAdapter(adapter);

    fetchNewsFeed();

    //if user swipes the recycler then refresh content page
    swipeRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
        @Override
        public void onRefresh() {
            fetchNewsFeed();
        }
    });
}

private void initialize() {
    swipeRefreshLayout = findViewById(R.id.swipeRefresh_rssFeed);
    recyclerView_rssFeed = findViewById(R.id.recyclerView_rssFeed);

    listResponseModel = new ArrayList<>();
}

private void fetchNewsFeed() {
    String url = "here is my news feed url";
    StringRequest request = new StringRequest(Request.Method.GET, url, new Response.Listener<String>() {
        @Override
        public void onResponse(String response) {
            listResponseModel.clear();
            try {
                listResponseModel = parseNewsFeed(response);
            } catch (XmlPullParserException | IOException e) {
                Log.e(TAG, e.getMessage());
            }
            adapter.notifyDataSetChanged();
        }
    }, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {

        }
    });
    RequestQueue queue = Volley.newRequestQueue(this);
    queue.add(request);

}

private List<RssModel> parseNewsFeed(String response) throws XmlPullParserException,
        IOException {

    XmlPullParserFactory parserFactory = XmlPullParserFactory.newInstance();
    parserFactory.setNamespaceAware(true);
    XmlPullParser xmlPullParser = parserFactory.newPullParser();
    xmlPullParser.setFeature(XmlPullParser.FEATURE_PROCESS_NAMESPACES, false);
    xmlPullParser.setInput(new StringReader(response));

    return processParsing(xmlPullParser);
}

private List<RssModel> processParsing(XmlPullParser xmlPullParser) throws IOException, XmlPullParserException {
    List<RssModel> listRssFeed = new ArrayList<>();
    int eventType = xmlPullParser.getEventType();
    RssModel rssModel = null;

    xmlPullParser.nextTag();
    while (eventType != XmlPullParser.END_DOCUMENT) {
        String eltName;
        switch (eventType) {
            case XmlPullParser.START_DOCUMENT:
                break;
            case XmlPullParser.START_TAG:
                eltName = xmlPullParser.getName();
                if ("item".equals(eltName)) {
                    rssModel = new RssModel();
                } else if (rssModel != null) {
                    if ("title".equals(eltName)) {
                        String title = xmlPullParser.nextText();
                        rssModel.setTitle(title);
                        Log.d(TAG, "title: " + title);
                    } else if ("link".equals(eltName)) {
                        String link = xmlPullParser.nextText();
                        rssModel.setLink(link);
                        Log.d(TAG, "link: " + link);
                    }
                }
                break;
            case XmlPullParser.END_TAG:
                eltName = xmlPullParser.getName();
                if ("item".equals(eltName) && rssModel != null) {
                    listRssFeed.add(rssModel);
                }
                break;
        }
        eventType = xmlPullParser.next();
    }
    return listRssFeed;
}
}

我的xml设计是:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="rssnewsfeed.RssNewsActivity">

<android.support.v4.widget.SwipeRefreshLayout
    android:id="@+id/swipeRefresh_rssFeed"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/recyclerView_rssFeed"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
</android.support.v4.widget.SwipeRefreshLayout>

</RelativeLayout>

这是我的适配器类

public class RssFeedAdapter extends RecyclerView.Adapter<RssFeedAdapter.RssViewHolder> {
private Context mContext;
private List<RssModel> mRssFeeds;

public RssFeedAdapter(Context mContext, List<RssModel> mRssFeeds) {
    this.mContext = mContext;
    this.mRssFeeds = mRssFeeds;
}

@NonNull
@Override
public RssViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
    View v = LayoutInflater.from(mContext).inflate(R.layout.rss_feed_layout, viewGroup, false);
    return new RssViewHolder(v);
}

@Override
public void onBindViewHolder(@NonNull RssViewHolder rssViewHolder, int i) {
    RssModel post = mRssFeeds.get(i);

    rssViewHolder.textView_title.setText(post.getTitle());
    rssViewHolder.textView_link.setText(post.getLink());
}

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

public class RssViewHolder extends RecyclerView.ViewHolder {
    private TextView textView_title, textView_link;

    public RssViewHolder(@NonNull View itemView) {
        super(itemView);
        textView_title = itemView.findViewById(R.id.textView_title);
        textView_link = itemView.findViewById(R.id.textView_link);
    }

}
}

最后这是我的模型类:

public class RssModel {
private String title;
private String link;

public RssModel() {
}

public String getTitle() {
    return title;
}

public void setTitle(String title) {
    this.title = title;
}

public String getLink() {
    return link;
}

public void setLink(String link) {
    this.link = link;
}
}

我尝试了很多方法，但没有成功。我不知道我错过了什么。我将不胜感激任何指导。谢谢。

Answer 1

给出“=”将创建一个ArrayList的新实例，除此之外已经绑定(bind)到RecyclerView适配器。

所以，你需要改变这个，

listResponseModel = parseNewsFeed(response);

至

listResponseModel.addAll(parseNewsFeed(response));