我正在构建用于显示RSS源的Android应用程序，在一个活动中，我在EditText中编写RSS链接并单击按钮，然后显示RSS源（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：
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;
}
}
答案 0 :(得分：0)
您正在将项目直接添加到RSSListAdapter（adapter），但您永远不会删除或清除之前已添加的项目。由于RSSListAdapter不受newsItemList支持，因此清除该列表只会阻止旧项目再次添加。
在添加新项目之前致电adapter.clear()，或让adapter支持newsItemList。