Question

好的，所以我试图在Android中使用ListView创建一个RSS应用程序。我有2个类读取html并返回包含标题，描述和链接的对象数组。

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";
    }
}

和

 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;
    }

}

我用Java测试了java类，它们工作得很好，它返回一个包含标题，描述和链接的10个故事的数组。我的问题是我现在需要使用此数据字段在我的Android应用程序中填充ListView。我在将信息连接到ListView时遇到问题。我试过一个适配器，但我并不是很了解适配器。任何指针都将非常感激。

我尝试过的片段就是这个

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

如果您使用的是ListView，则需要一个适配器。适配器位于ListView和数据之间。

您需要创建一个继承自Adapter的新Adapter类。在它的构造函数中，您传递了NewsStory的数组。然后，在getView（）中，您将实例化ListView行布局，并将NewsStory对应的所有数据填入该位置。

这是适配器的基本功能。您可以了解详情并查看示例here。

一旦了解了适配器的工作原理，我强烈建议您将ListView切换到RecyclerView并开始使用ViewHolder模式，这对列表性能和RAM使用有很大帮助。

RSS应用程序，我的ListView有问题

1 个答案: