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Upgrade and simplicity issue - Trying to build RSS reader for Android

I am trying to load XML data using Retrofit and parse it using Simple and then load it into a ListView.

Unfortunately, the downloaded data will not be displayed on the screen. Can anyone tell me where is the problem please?

This is my model:

@Root(name = "item")
public class Article {
    @Element(name = "title")
    private String title;
    @Element(name = "author")
    private String author;
    @Element(name = "description")
    private String description;

Code for interface:

public interface Service {
    @GET("/rss/news")
    public void getArticle(Callback<List<Article>> callback);
}

Snippet code:

public class ArticlePreviewFragment extends Fragment {

    protected ArticlePreviewAdapter adapter;
    protected List<Article> previewList;
    private ListView listView;

    public ArticlePreviewFragment() {}

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        previewList = new ArrayList<>();
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_article_preview, container, false);
        listView = (ListView) view.findViewById(R.id.previewList);
        return view;
    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        adapter = new ArticlePreviewAdapter(getActivity(), previewList);
        listView.setAdapter(adapter);

        RestAdapter restAdapter = new RestAdapter.Builder()
                .setLogLevel(RestAdapter.LogLevel.FULL)
                .setEndpoint("http://muse.mu")
                .setConverter(new SimpleXMLConverter())
                .build();

        Service service = restAdapter.create(Service.class);

        Callback<List<Article>> callback = new Callback<List<Article>>() {
            @Override
            public void success(List<Article> articles, Response response) {
                adapter.clear();
                adapter.addAll(articles);
                adapter.notifyDataSetChanged();
            }

            @Override
            public void failure(RetrofitError error)
        };
        service.getArticle(callback);
    }
}

I am using the converter found here - I copied it to my retrofit / converter / SimpleXMLConverter.java project

Finally, the code for the adapter:

public class ArticlePreviewAdapter extends ArrayAdapter<Article> {
    List<Article> articlePreviewItems;
    public ArticlePreviewAdapter(Activity activity, List<Article> articlePreviewItems) {
        super(activity, R.layout.item_article_preview, articlePreviewItems);
        this.articlePreviewItems = articlePreviewItems;
    }

    private static class ViewHolder {
        TextView articlePreviewTitle;
        TextView articlePreviewAuthor;
        TextView articlePreviewDescription;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder viewHolder;
        Article articlePreviewItem = getItem(position);

        if (convertView == null) {
            viewHolder = new ViewHolder();
            LayoutInflater inflater = LayoutInflater.from(getContext());
            convertView = inflater.inflate(R.layout.item_article_preview, parent, false);
            viewHolder.articlePreviewTitle = (TextView) convertView.findViewById(R.id.articleTitle);
            viewHolder.articlePreviewAuthor = (TextView) convertView.findViewById(R.id.articleAuthor);
            viewHolder.articlePreviewDescription = (TextView) convertView.findViewById(R.id.articleDescription);
            convertView.setTag(viewHolder);
        } else {
            viewHolder = (ViewHolder) convertView.getTag();
        }

        viewHolder.articlePreviewTitle.setText(articlePreviewItem.getTitle());
        viewHolder.articlePreviewAuthor.setText(articlePreviewItem.getAuthor());
        viewHolder.articlePreviewDescription.setText(articlePreviewItem.getDescription());

        return convertView;
    }
}

EDIT: I added error.printStackTrace (); in the failure method and found this in logcat:

rss.reader W/System.err﹕ retrofit.RetrofitError: java.lang.ClassCastException: libcore.reflect.ParameterizedTypeImpl cannot be cast to java.lang.Class
rss.reader W/System.err﹕ at retrofit.RestAdapter$RestHandler.invokeRequest(RestAdapter.java:378)
rss.reader W/System.err﹕ at retrofit.RestAdapter$RestHandler.access$100(RestAdapter.java:220)
rss.reader W/System.err﹕ at retrofit.RestAdapter$RestHandler$2.obtainResponse(RestAdapter.java:278)
rss.reader W/System.err﹕ at retrofit.CallbackRunnable.run(CallbackRunnable.java:42)
rss.reader W/System.err﹕ at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
rss.reader W/System.err﹕ at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
rss.reader W/System.err﹕ at retrofit.Platform$Android$2$1.run(Platform.java:142)
rss.reader W/System.err﹕ at java.lang.Thread.run(Thread.java:818)
rss.reader W/System.err﹕ Caused by: retrofit.converter.ConversionException: java.lang.ClassCastException: libcore.reflect.ParameterizedTypeImpl cannot be cast to java.lang.Class
rss.reader W/System.err﹕ at rss.reader.SimpleXMLConverter.fromBody(SimpleXMLConverter.java:39)
rss.reader W/System.err﹕ at retrofit.RestAdapter$RestHandler.invokeRequest(RestAdapter.java:362)
rss.reader W/System.err﹕ ... 7 more
rss.reader W/System.err﹕ Caused by: java.lang.ClassCastException: libcore.reflect.ParameterizedTypeImpl cannot be cast to java.lang.Class
rss.reader W/System.err﹕ at rss.reader.SimpleXMLConverter.fromBody(SimpleXMLConverter.java:37)
rss.reader W/System.err﹕ ... 8 more
rss.reader W/System.err﹕ retrofit.RetrofitError: java.lang.ClassCastException: libcore.reflect.ParameterizedTypeImpl cannot be cast to java.lang.Class
rss.reader W/System.err﹕ at retrofit.RestAdapter$RestHandler.invokeRequest(RestAdapter.java:378)
rss.reader W/System.err﹕ at retrofit.RestAdapter$RestHandler.access$100(RestAdapter.java:220)
rss.reader W/System.err﹕ at retrofit.RestAdapter$RestHandler$2.obtainResponse(RestAdapter.java:278)
rss.reader W/System.err﹕ at retrofit.CallbackRunnable.run(CallbackRunnable.java:42)
rss.reader W/System.err﹕ at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
rss.reader W/System.err﹕ at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
rss.reader W/System.err﹕ at retrofit.Platform$Android$2$1.run(Platform.java:142)
rss.reader W/System.err﹕ at java.lang.Thread.run(Thread.java:818)
rss.reader W/System.err﹕ Caused by: retrofit.converter.ConversionException: java.lang.ClassCastException: libcore.reflect.ParameterizedTypeImpl cannot be cast to java.lang.Class
rss.reader W/System.err﹕ at rss.reader.SimpleXMLConverter.fromBody(SimpleXMLConverter.java:39)
rss.reader W/System.err﹕ at retrofit.RestAdapter$RestHandler.invokeRequest(RestAdapter.java:362)
rss.reader W/System.err﹕ ... 7 more
rss.reader W/System.err﹕ Caused by: java.lang.ClassCastException: libcore.reflect.ParameterizedTypeImpl cannot be cast to java.lang.Class
rss.reader W/System.err﹕ at rss.reader.SimpleXMLConverter.fromBody(SimpleXMLConverter.java:37)
rss.reader W/System.err﹕ ... 8 more
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3 answers


Jake Wharton's answer eventually led me to the final solution as shown below. The source of the problem really lay in the type that was called back. It was misspelled.

Some people may find this helpful by the way; Converting XML or JSON to Java Pojo Classes - Online .

By default, Simple treats elements as required fields and is strict when it comes to defining the root element. This is mentioned in a tutorial on the official site.

RSS.java

@Root(name = "rss", strict = false)
public class RSS {
    @Element
    private Channel channel;
    @Attribute
    private String version;

    public Channel getChannel() {
        return channel;
    }
}


Channel.java

@Root(name = "channel", strict = false)
public class Channel {
    @ElementList(name = "item", inline = true)
    List<Article> articleList;
    @Element
    private String title;
    @Element
    private String link;
    @Element
    private String description;

Article.java

@Root(name = "item", strict = false)
public class Article {
    @Element
    private String title;
    @Element
    private String description;
    @Element
    private String link;
    @Element(required = false)
    private String author;
    @Element(required = false)
    private String pubDate;
+4


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This is an update error. Please post a GitHub issue in the project.

As a workaround, don't use a generic type as the top-level type for now.



public final class ArticleList extends ArrayList<Article> {
}

public interface Service {
  @GET("/rss/news")
  public void getArticle(Callback<ArticleList> callback);
}
+5


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I think the RetroFit website should clearly state: Generic variables are not allowed for use in response types .

Source: Issue # 807 on GitHub.

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