Problems with Retrofit and Simple – Try making an RSS reader for Android… here is a solution to the problem.
Problems with Retrofit and Simple – Try making an RSS reader for Android
I’m trying to use Retrofit to download XML data and parse it with Simple and load it into a ListView.
Unfortunately, the downloaded data does not appear on the screen. Can anyone tell me what the problem is?
Here 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;
Interface code:
public interface Service {
@GET("/rss/news")
public void getArticle(Callback<List<Article>> callback);
}
fragment 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’m using the converter found here – I’ve copied it into my project retrofit/converter/SimpleXMLConverter.java
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 failed method, find 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
Solution
This is a Retrofit bug. Please submit a GitHub issue about the project.
As a workaround for now, do not use generic types as top-level types.
public final class ArticleList extends ArrayList<Article> {
}
public interface Service {
@GET("/rss/news")
public void getArticle(Callback<ArticleList> callback);
}