Question

我正在为一个活动中的Show RSS feed构建Android应用程序，我在EditText中编写RSS链接并单击按钮，然后显示RSS提要（新闻）。

当我进入RSS链接并在第一次点击按钮时，正常显示新闻，但我的问题是当我输入新的链接＆amp;按下按钮：新链接的新闻出现在旧消息下（我在EditText中输入的第一个链接的消息）。

但是，当我按下按钮时，我想删除旧消息并显示新链接的RSS提要。

有什么想法吗？

提前致谢。

我的代码：

在MainActivity中：

import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;

import org.w3c.dom.DOMException;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

import android.app.Activity;
import android.app.ProgressDialog;
import android.content.res.Resources;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.os.Handler;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.Button;
import android.widget.EditText;
import android.widget.LinearLayout;
import android.widget.Toast;

public class MainActivity extends Activity {

    private static final String TAG = "MainActivity";

    private static String rss_url = "http://www.thehindu.com/news/cities/chennai/chen-health/?service=rss";

    ProgressDialog progressDialog;
    Handler handler = new Handler();

    RSSListView list;
    RSSListAdapter adapter;
    ArrayList<RSSNewsItem> newsItemList;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        ViewGroup.LayoutParams params = new ViewGroup.LayoutParams(
                ViewGroup.LayoutParams.MATCH_PARENT,
                ViewGroup.LayoutParams.MATCH_PARENT);
        list = new RSSListView(this);

        adapter = new RSSListAdapter(this);
        list.setAdapter(adapter);
        list.setOnDataSelectionListener(new OnDataSelectionListener() {
            public void onDataSelected(AdapterView parent, View v,
                    int position, long id) {
                RSSNewsItem curItem = (RSSNewsItem) adapter.getItem(position);
                String curTitle = curItem.getTitle();

                Toast.makeText(getApplicationContext(),
                        "Selected : " + curTitle, 1000).show();
            }
        });

        newsItemList = new ArrayList<RSSNewsItem>();
        LinearLayout mainLayout = (LinearLayout) findViewById(R.id.mainLayout);
        mainLayout.addView(list, params);

        final EditText edit01 = (EditText) findViewById(R.id.edit01);
        edit01.setText(rss_url);

        Button show_btn = (Button) findViewById(R.id.show_btn);
        show_btn.setOnClickListener(new OnClickListener() {

            public void onClick(View v) {
                String inputStr = edit01.getText().toString();
                showRSS(inputStr);
            }

        });

    }

    private void showRSS(String urlStr) {
        try {
            progressDialog = ProgressDialog.show(this, "RSS Refresh",
                    "RSS Lodeing..", true, true);

            RefreshThread thread = new RefreshThread(urlStr);
            thread.start();

        } catch (Exception e) {
            Log.e(TAG, "Error", e);
        }
    }

    class RefreshThread extends Thread {
        String urlStr;

        public RefreshThread(String str) {
            urlStr = str;
        }

        public void run() {

            try {
                DocumentBuilderFactory builderFactory = DocumentBuilderFactory
                        .newInstance();
                DocumentBuilder builder = builderFactory.newDocumentBuilder();

                URL urlForHttp = new URL(urlStr);

                InputStream instream = getInputStreamUsingHTTP(urlForHttp);
                // parse
                Document document = builder.parse(instream);
                int countItem = processDocument(document);
                Log.d(TAG, countItem + " news item processed.");

                // post for the display of fetched RSS info.
                handler.post(updateRSSRunnable);

            } catch (Exception ex) {
                ex.printStackTrace();
            }

        }
    }

    public InputStream getInputStreamUsingHTTP(URL url) throws Exception {
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setRequestMethod("GET");
        conn.setDoInput(true);
        conn.setDoOutput(true);
        conn.setUseCaches(false);
        conn.setAllowUserInteraction(false);

        int resCode = conn.getResponseCode();
        Log.d(TAG, "Response Code : " + resCode);

        InputStream instream = conn.getInputStream();

        return instream;
    }

    private int processDocument(Document doc) {
        newsItemList.clear();

        Element docEle = doc.getDocumentElement();
        NodeList nodelist = docEle.getElementsByTagName("item");
        int count = 0;
        if ((nodelist != null) && (nodelist.getLength() > 0)) {
            for (int i = 0; i < nodelist.getLength(); i++) {

                RSSNewsItem newsItem = dissectNode(nodelist, i);
                if (newsItem != null) {
                    newsItemList.add(newsItem);
                    count++;
                }
            }
        }

        return count;
    }

    private RSSNewsItem dissectNode(NodeList nodelist, int index) {
        RSSNewsItem newsItem = null;

        try {
            Element entry = (Element) nodelist.item(index);

            Element title = (Element) entry.getElementsByTagName("title").item(
                    0);
            Element link = (Element) entry.getElementsByTagName("link").item(0);
            Element description = (Element) entry.getElementsByTagName(
                    "description").item(0);

            NodeList pubDataNode = entry.getElementsByTagName("pubDate");
            if (pubDataNode == null) {
                pubDataNode = entry.getElementsByTagName("dc:date");
            }
            Element pubDate = (Element) pubDataNode.item(0);

            Element author = (Element) entry.getElementsByTagName("author")
                    .item(0);
            Element category = (Element) entry.getElementsByTagName("category")
                    .item(0);

            String titleValue = null;
            if (title != null) {
                Node firstChild = title.getFirstChild();
                if (firstChild != null) {
                    titleValue = firstChild.getNodeValue();
                }
            }
            String linkValue = null;
            if (link != null) {
                Node firstChild = link.getFirstChild();
                if (firstChild != null) {
                    linkValue = firstChild.getNodeValue();
                }
            }

            String descriptionValue = null;
            if (description != null) {
                Node firstChild = description.getFirstChild();
                if (firstChild != null) {
                    descriptionValue = firstChild.getNodeValue();
                }
            }

            String pubDateValue = null;
            if (pubDate != null) {
                Node firstChild = pubDate.getFirstChild();
                if (firstChild != null) {
                    pubDateValue = firstChild.getNodeValue();
                }
            }

            String authorValue = null;
            if (author != null) {
                Node firstChild = author.getFirstChild();
                if (firstChild != null) {
                    authorValue = firstChild.getNodeValue();
                }
            }

            String categoryValue = null;
            if (category != null) {
                Node firstChild = category.getFirstChild();
                if (firstChild != null) {
                    categoryValue = firstChild.getNodeValue();
                }
            }

            Log.d(TAG, "item node : " + titleValue + ", " + linkValue + ", "
                    + descriptionValue + ", " + pubDateValue + ", "
                    + authorValue + ", " + categoryValue);

            newsItem = new RSSNewsItem(titleValue, linkValue, descriptionValue,
                    pubDateValue, authorValue, categoryValue);

        } catch (DOMException e) {
            e.printStackTrace();
        }

        return newsItem;
    }

    Runnable updateRSSRunnable = new Runnable() {
        public void run() {

            try {

                Resources res = getResources();
                Drawable rssIcon = res.getDrawable(R.drawable.rss_icon);
                for (int i = 0; i < newsItemList.size(); i++) {
                    RSSNewsItem newsItem = (RSSNewsItem) newsItemList.get(i);
                    newsItem.setIcon(rssIcon);
                    adapter.addItem(newsItem);
                }

                adapter.notifyDataSetChanged();

                progressDialog.dismiss();
            } catch (Exception ex) {
                ex.printStackTrace();
            }

        }
    };

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

}

并在OnDataSelectionListener类中：

public interface OnDataSelectionListener {


    public void onDataSelected(AdapterView parent, View v, int position, long id);

}

并在RSSListAdapter中：

public class RSSListAdapter extends BaseAdapter {

    private Context mContext;

    private List<RSSNewsItem> mItems = new ArrayList<RSSNewsItem>();

    public RSSListAdapter(Context context) {
        mContext = context;
    }

    public void addItem(RSSNewsItem it) {
        mItems.add(it);
    }

    public void setListItems(List<RSSNewsItem> lit) {
        mItems = lit;
    }

    public int getCount() {
        return mItems.size();
    }

    public Object getItem(int position) {
        return mItems.get(position);
    }

    public boolean areAllItemsSelectable() {
        return false;
    }

    public boolean isSelectable(int position) {
        return true;
    }

    public long getItemId(int position) {
        return position;
    }

    public View getView(int position, View convertView, ViewGroup parent) {
        RSSNewsItemView itemView;
        if (convertView == null) {
            itemView = new RSSNewsItemView(mContext, mItems.get(position));
        } else {
            itemView = (RSSNewsItemView) convertView;

            itemView.setIcon(mItems.get(position).getIcon());
            itemView.setText(0, mItems.get(position).getTitle());
            itemView.setText(1, mItems.get(position).getPubDate());
            itemView.setText(2, mItems.get(position).getCategory());
            itemView.setText(3, mItems.get(position).getDescription());
        }

        return itemView;
    }

}

并在RSSListView类中：

public class RSSListView extends ListView {
    /**
     * DataAdapter for this instance
     */
    private RSSListAdapter adapter;

    /**
     * Listener for data selection
     */
    private OnDataSelectionListener selectionListener;

    public RSSListView(Context context) {
        super(context);

        init();
    }

    public RSSListView(Context context, AttributeSet attrs) {
        super(context, attrs);

        init();
    }

    /**
     * set initial properties
     */
    private void init() {
        // set OnItemClickListener for processing OnDataSelectionListener
        setOnItemClickListener(new OnItemClickAdapter());
    }

    /**
     * set DataAdapter
     * 
     * @param adapter
     */
    public void setAdapter(BaseAdapter adapter) {
        super.setAdapter(adapter);

    }

    /**
     * get DataAdapter
     * 
     * @return
     */
    public BaseAdapter getAdapter() {
        return (BaseAdapter) super.getAdapter();
    }

    /**
     * set OnDataSelectionListener
     * 
     * @param listener
     */
    public void setOnDataSelectionListener(OnDataSelectionListener listener) {
        this.selectionListener = listener;
    }

    /**
     * get OnDataSelectionListener
     * 
     * @return
     */
    public OnDataSelectionListener getOnDataSelectionListener() {
        return selectionListener;
    }

    class OnItemClickAdapter implements OnItemClickListener {

        public OnItemClickAdapter() {

        }

        public void onItemClick(AdapterView parent, View v, int position,
                long id) {

            if (selectionListener == null) {
                return;
            }

            // get row and column
            int rowIndex = -1;
            int columnIndex = -1;

            // call the OnDataSelectionListener method
            selectionListener.onDataSelected(parent, v, position, id);

        }

    }

}

并在RSSNewsItem类中：

public class RSSNewsItem {

    private String title;
    private String link;
    private String description;
    private String pubDate;
    private String author;
    private String category;

    private Drawable mIcon;

    /**
     * Initialize with icon and data array
     */
    public RSSNewsItem() {
    }

    /**
     * Initialize with icon and strings
     */
    public RSSNewsItem(String title, String link, String description, String pubDate, String author, String category) {
        this.title = title;
        this.link = link;
        this.description = description;
        this.pubDate = pubDate;
        this.author = author;
        this.category = category;
    }

    /**
     * Set icon
     * 
     * @param icon
     */
    public void setIcon(Drawable icon) {
        mIcon = icon;
    }

    /**
     * Get icon
     * 
     * @return
     */
    public Drawable getIcon() {
        return mIcon;
    }

    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;
    }

    public String getDescription() {
        return description;
    }

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

    public String getPubDate() {
        return pubDate;
    }

    public void setPubDate(String pubDate) {
        this.pubDate = pubDate;
    }

    public String getAuthor() {
        return author;
    }

    public void setAuthor(String author) {
        this.author = author;
    }

    public String getCategory() {
        return category;
    }

    public void setCategory(String category) {
        this.category = category;
    }

    /**
     * Compare with the input object
     * 
     * @param other
     * @return
     */
    public int compareTo(RSSNewsItem other) {
        if (title.equals(other.getTitle())) {
            return -1;
        } else if (link.equals(other.getLink())) {
            return -1;
        } else if (description.equals(other.getDescription())) {
            return -1;
        } else if (pubDate.equals(other.getPubDate())) {
            return -1;
        } else if (author.equals(other.getAuthor())) {
            return -1;
        } else if (category.equals(other.getCategory())) {
            return -1;
        }

        return 0;
    }

}

最后，在RSSNewsItemView类中：

public class RSSNewsItem {

    private String title;
    private String link;
    private String description;
    private String pubDate;
    private String author;
    private String category;

    private Drawable mIcon;

    /**
     * Initialize with icon and data array
     */
    public RSSNewsItem() {
    }

    /**
     * Initialize with icon and strings
     */
    public RSSNewsItem(String title, String link, String description, String pubDate, String author, String category) {
        this.title = title;
        this.link = link;
        this.description = description;
        this.pubDate = pubDate;
        this.author = author;
        this.category = category;
    }

    /**
     * Set icon
     * 
     * @param icon
     */
    public void setIcon(Drawable icon) {
        mIcon = icon;
    }

    /**
     * Get icon
     * 
     * @return
     */
    public Drawable getIcon() {
        return mIcon;
    }

    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;
    }

    public String getDescription() {
        return description;
    }

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

    public String getPubDate() {
        return pubDate;
    }

    public void setPubDate(String pubDate) {
        this.pubDate = pubDate;
    }

    public String getAuthor() {
        return author;
    }

    public void setAuthor(String author) {
        this.author = author;
    }

    public String getCategory() {
        return category;
    }

    public void setCategory(String category) {
        this.category = category;
    }

    /**
     * Compare with the input object
     * 
     * @param other
     * @return
     */
    public int compareTo(RSSNewsItem other) {
        if (title.equals(other.getTitle())) {
            return -1;
        } else if (link.equals(other.getLink())) {
            return -1;
        } else if (description.equals(other.getDescription())) {
            return -1;
        } else if (pubDate.equals(other.getPubDate())) {
            return -1;
        } else if (author.equals(other.getAuthor())) {
            return -1;
        } else if (category.equals(other.getCategory())) {
            return -1;
        }

        return 0;
    }

}

Answer 1

我认为您需要拨打adapter.clear()并在点击按钮时再次使用adapter.notifyDataSet()使列表无效。

RSS Feeder Android应用程序

1 个答案: