RSS应用程序，我的ListView遇到问题

Question

Ok so I'm trying to make an RSS app using ListView in android. I have 2 classes that reads the html and returns an array of objects containing the title, description, and link.

public class RSS
{
    public static NewsStory[] readRSS(String urlAddress)
    {
        try{
            NewsStory[] stories = new NewsStory[10];
            URL rssUrl = new URL(urlAddress);
            BufferedReader in = new BufferedReader(new InputStreamReader(rssUrl.openStream()));
            String rawString;
            String item = "";
            int i = 0;
            while((rawString = in.readLine()) != null)
            {
                if(rawString.contains("<item>"))
                {

                    int titleEndIndex = 0;
                    int titleStartIndex = 0;
                    while (titleStartIndex >= 0 && i < 10)
                    {
                        titleStartIndex = rawString.indexOf("<item>", titleEndIndex);
                        if (titleStartIndex >= 0)
                        {
                            titleEndIndex = rawString.indexOf("</item>", titleStartIndex);
                            item = rawString.substring(titleStartIndex + "<item>".length(), titleEndIndex) + "\n";
                        }
                        stories[i] = new NewsStory(getContent(item,"title"),getContent(item,"description"),getContent(item,"link"));
                        i++;
                    }
                    in.close();
                    return stories;
                }
            }
        }
        catch(MalformedURLException ue)
        {
            System.out.print("Malformed URL");
        }
        catch(IOException ioe)
        {
            System.out.print("Something went wrong reading the contents");
        }
        return null;
    }

    public static String getContent(String item, String target)
    {
        String excerpt = "";
        int titleEndIndex = 0;
        int titleStartIndex = 0;
        while (titleStartIndex >= 0) {
            titleStartIndex = item.indexOf("<"+target+">", titleEndIndex);
            if (titleStartIndex >= 0) {
                if (target.equals("description"))
                    titleEndIndex = item.indexOf("&", titleStartIndex);
                else
                    titleEndIndex = item.indexOf("</"+target+">", titleStartIndex);
                excerpt += item.substring(titleStartIndex + ("<"+target+">").length(), titleEndIndex) + "\n";

            }
            return excerpt;
        }
        return "error";
    }
}

and

 public class NewsStory {

    String title;
    String description;
    String link;


    public NewsStory()
    {
        this.title = "";
        this.description = "";
        this.link = "";
    }
    public NewsStory(String title, String description, String link) {
        this.title = title;
        this.description = description;
        this.link = link;
    }

    public String getTitle() {
        return title;
    }

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

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public String getLink() {
        return link;
    }

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

}

I tested the java classes in Java, and they work perfectly, it returns an array with 10 stories containing title, description, and link. My problem is that I need to now populate the ListView in my android app using the data fields from this. I'm having trouble connecting the info to the ListView. I tried an adapter, but I don't really understand adapters. Any pointers would be greatly appreciated.

the fragment that I'm trying it in is this

public class HeadlineFragment extends Fragment {

    EditText input;
    Button search;
    ListView headlines;
    private NewsDataSource ds;
    private ListView newsListView;

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

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View v = inflater.inflate(R.layout.fragment_headline,container,false);
        ds = new NewsDataSource();
        newsListView = (ListView)v.findViewById(R.id.listView);
        //newsListView.setAdapter(new NewsDataSourceAdapter());

        input = (EditText)v.findViewById(R.id.txtInput);
        search = (Button)v.findViewById(R.id.btnSearch);
        headlines = (ListView)v.findViewById(R.id.listView);

        return v;
    }

}

Answer 1

If you're using a ListView, you need an Adapter. Adapter are in between your ListView and your data.

You need to create a new Adapter class that inherits from Adapter. In its constructor, you pass your array of NewsStory's. Then, in getView() you instatiate the ListView row layout and fill in all the data from the NewsStory correspoding to that position.

This is the basics functioning of an Adapter. You can learn more and see examples here .

Once you understand how Adapters work, I'd strongly suggest you switch ListView into RecyclerView and start using the ViewHolder pattern, which greatly helps with lists performance and RAM usage.