本文概述
- Android RSS Feed阅读器示例
RSS阅读器的XML格式包含以下标记。
<
channel>
<
title><
/title>
<
link><
/link>
<
description><
/description>
<
item>
<
title><
/title>
<
link><
/link>
<
pubDate><
/pubDate>
<
description><
/description>
<
/item>
<
item>
.
.
.
.
<
/item>
<
/channel>在本教程中，我们将使用Android RSS Feed阅读器阅读网站的内容（Rediff.com和Cinemablend.com）。内容显示在Android的ListView中，单击这些项目将加载其各自的URL。
Android RSS Feed阅读器示例使用以下代码创建活动MainActivity.java。单击此活动的按钮，将重定向到RSSFeedActivity.java类，并加载给定URL的内容。
activity_main.xml
<
?xml version="1.0" encoding="utf-8"?>
<
RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"><
Button
android:id="@+id/btnRediff"
android:layout_width="300dp"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true"
android:layout_marginBottom="101dp"
android:text="REDIFF RSS FEED" /><
Button
android:id="@+id/btnCinemaBlend"
android:layout_width="300dp"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/btnRediff"
android:layout_alignParentBottom="true"
android:layout_alignStart="@+id/btnRediff"
android:layout_marginBottom="28dp"
android:text="CINEMA BLEND RSS FEED" />
<
/RelativeLayout>MainActivity.java
package example.srcmini.com.androidrssfeed;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.content.Intent;
import android.view.View;
import android.widget.Button;
import java.util.ArrayList;
public class MainActivity extends AppCompatActivity implements View.OnClickListener {ArrayList<
String> rssLinks = new ArrayList<
>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button btnRediff = findViewById(R.id.btnRediff);
Button btnCinemaBlend = findViewById(R.id.btnCinemaBlend);
btnRediff.setOnClickListener(this);
btnCinemaBlend.setOnClickListener(this);
rssLinks.add("http://www.rediff.com/rss/moviesreviewsrss.xml");
rssLinks.add("http://www.cinemablend.com/rss_review.php");
}@Override
public void onClick(View view) {
Intent intent = new Intent(getApplicationContext(), RSSFeedActivity.class);
switch (view.getId()) {
case R.id.btnRediff:
intent.putExtra("rssLink", rssLinks.get(0));
startActivity(intent);
break;
case R.id.btnCinemaBlend:
intent.putExtra("rssLink", rssLinks.get(1));
startActivity(intent);
break;
}
}
}创建一个布局rss_item_list_row.xml，其中包含在RSS Feed中显示的新闻通讯的字段（页面URL，标题，发布日期）。
rss_item_list_row.xml
<
?xml version="1.0" encoding="utf-8"?>
<
RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="8dip"><
TextView
android:id="@+id/page_url"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:visibility="gone" /><
TextView
android:id="@+id/title"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:paddingBottom="1dip"
android:textColor="#212121"
android:textSize="18sp"
android:textStyle="bold" /><
TextView
android:id="@+id/pub_date"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@id/title"
android:paddingBottom="3dip"
android:textColor="#9b737775"
android:textSize="14sp" /><
/RelativeLayout>RSSItem.java
package example.srcmini.com.androidrssfeed;
public class RSSItem {
public String title;
public String link;
public String description;
public String pubdate;
public String guid;
public RSSItem(String title, String link, String description, String pubdate, String guid) {
this.title = title;
this.link = link;
this.description = description;
this.pubdate = pubdate;
this.guid = guid;
}
}【android rss阅读器】在此类中创建RSSParser.java类；我们将使用DocumentBuilderFactory类的实例来解析XML文档。
RSSParser.java
package example.srcmini.com.androidrssfeed;
import android.util.Log;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.util.EntityUtils;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import java.io.IOException;
import java.io.StringReader;
import java.io.UnsupportedEncodingException;
import java.util.ArrayList;
import java.util.List;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
public class RSSParser {// RSS XML document CHANNEL tag
private static String TAG_CHANNEL = "channel";
private static String TAG_TITLE = "title";
private static String TAG_LINK = "link";
private static String TAG_DESRIPTION = "description";
private static String TAG_ITEM = "item";
private static String TAG_PUB_DATE = "pubDate";
private static String TAG_GUID = "guid";
public RSSParser() {
}public List<
RSSItem> getRSSFeedItems(String rss_url) {
List<
RSSItem> itemsList = new ArrayList<
RSSItem>();
String rss_feed_xml;
rss_feed_xml = this.getXmlFromUrl(rss_url);
if (rss_feed_xml != null) {
try {
Document doc = this.getDomElement(rss_feed_xml);
NodeList nodeList = doc.getElementsByTagName(TAG_CHANNEL);
Element e = (Element) nodeList.item(0);
NodeList items = e.getElementsByTagName(TAG_ITEM);
for (int i = 0;
i <
items.getLength();
i++) {
Element e1 = (Element) items.item(i);
String title = this.getValue(e1, TAG_TITLE);
String link = this.getValue(e1, TAG_LINK);
String description = this.getValue(e1, TAG_DESRIPTION);
String pubdate = this.getValue(e1, TAG_PUB_DATE);
String guid = this.getValue(e1, TAG_GUID);
RSSItem rssItem = new RSSItem(title, link, description, pubdate, guid);
// adding item to list
itemsList.add(rssItem);
}
} catch (Exception e) {
// Check log for errors
e.printStackTrace();
}
}
return itemsList;
}public String getXmlFromUrl(String url) {
String xml = null;
try {
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(url);
HttpResponse httpResponse = httpClient.execute(httpGet);
HttpEntity httpEntity = httpResponse.getEntity();
xml = EntityUtils.toString(httpEntity);
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return xml;
}public Document getDomElement(String xml) {
Document doc = null;
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
try {DocumentBuilder db = dbf.newDocumentBuilder();
InputSource is = new InputSource();
is.setCharacterStream(new StringReader(xml));
doc = db.parse(is);
} catch (ParserConfigurationException e) {
Log.e("Error: ", e.getMessage());
return null;
} catch (SAXException e) {
Log.e("Error: ", e.getMessage());
return null;
} catch (IOException e) {
Log.e("Error: ", e.getMessage());
return null;
}
return doc;
}public final String getElementValue(Node elem) {
Node child;
if (elem != null) {
if (elem.hasChildNodes()) {
for (child = elem.getFirstChild();
child != null;
child = child
.getNextSibling()) {
if (child.getNodeType() == Node.TEXT_NODE || (child.getNodeType() == Node.CDATA_SECTION_NODE)) {
return child.getNodeValue();
}
}
}
}
return "";
}public String getValue(Element item, String str) {
NodeList n = item.getElementsByTagName(str);
return this.getElementValue(n.item(0));
}
}现在，使用以下代码创建活动RSSFeedActivity.java。此类使用AsyncTask类从后台URL中加载RSS Feed的项目。
activity_rssfeed.xml
<
?xml version="1.0" encoding="utf-8"?>
<
RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/relativeLayout"
android:orientation="vertical"><
ListView
android:id="@android:id/list"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:dividerHeight="1dp" />
<
/RelativeLayout>RSSFeedActivity.java
package example.srcmini.com.androidrssfeed;
import android.app.ListActivity;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.RelativeLayout;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import android.widget.Toast;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Locale;
public class RSSFeedActivity extends ListActivity {private ProgressBar pDialog;
ArrayList<
HashMap<
String, String>> rssItemList = new ArrayList<
>();
RSSParser rssParser = new RSSParser();
List<
RSSItem> rssItems = new ArrayList<
>();
private static String TAG_TITLE = "title";
private static String TAG_LINK = "link";
private static String TAG_PUB_DATE = "pubDate";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_rssfeed);
String rss_link = getIntent().getStringExtra("rssLink");
new LoadRSSFeedItems().execute(rss_link);
ListView lv = getListView();
lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {public void onItemClick(AdapterView<
?> parent, View view, int position, long id) {
Intent in = new Intent(getApplicationContext(), WebActivity.class);
String page_url = ((TextView) view.findViewById(R.id.page_url)).getText().toString().trim();
in.putExtra("url", page_url);
startActivity(in);
}
});
}public class LoadRSSFeedItems extends AsyncTask<
String, String, String> {@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressBar(RSSFeedActivity.this, null, android.R.attr.progressBarStyleLarge);
RelativeLayout relativeLayout = findViewById(R.id.relativeLayout);
RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(
RelativeLayout.LayoutParams.WRAP_CONTENT, RelativeLayout.LayoutParams.WRAP_CONTENT
);
layoutParams.addRule(RelativeLayout.CENTER_IN_PARENT);
pDialog.setLayoutParams(layoutParams);
pDialog.setVisibility(View.VISIBLE);
relativeLayout.addView(pDialog);
}@Override
protected String doInBackground(String... args) {
// rss link url
String rss_url = args[0];
// list of rss items
rssItems = rssParser.getRSSFeedItems(rss_url);
// looping through each item
for (final RSSItem item : rssItems) {
// creating new HashMap
if (item.link.toString().equals(""))
break;
HashMap<
String, String> map = new HashMap<
String, String>();
// adding each child node to HashMap key => value
String givenDateString = item.pubdate.trim();
SimpleDateFormat sdf = new SimpleDateFormat("EEE, d MMM yyyy HH:mm:ss Z");
try {
Date mDate = sdf.parse(givenDateString);
SimpleDateFormat sdf2 = new SimpleDateFormat("EEEE, dd MMMM yyyy - hh:mm a", Locale.US);
item.pubdate = sdf2.format(mDate);
} catch (ParseException e) {
e.printStackTrace();
}map.put(TAG_TITLE, item.title);
map.put(TAG_LINK, item.link);
map.put(TAG_PUB_DATE, item.pubdate);
// adding HashList to ArrayList
rssItemList.add(map);
}// updating UI from Background Thread
runOnUiThread(new Runnable() {
public void run() {
ListAdapter adapter = new SimpleAdapter(
RSSFeedActivity.this, rssItemList, R.layout.rss_item_list_row, new String[]{TAG_LINK, TAG_TITLE, TAG_PUB_DATE}, new int[]{R.id.page_url, R.id.title, R.id.pub_date});
// updating listview
setListAdapter(adapter);
}
});
return null;
}protected void onPostExecute(String args) {
pDialog.setVisibility(View.GONE);
}
}
}创建一个包含WebView的活动WebActivity.java，该活动将加载上一个活动中单击的链接的内容。
activity_web.xml
<
?xml version="1.0" encoding="utf-8"?>
<
RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:id="@+id/relativeLayout"
android:layout_height="match_parent"><
android.support.v4.widget.NestedScrollView
android:layout_width="match_parent"
android:layout_height="match_parent"><
WebView
android:id="@+id/webView"
android:layout_width="match_parent"
android:layout_height="match_parent" /><
/android.support.v4.widget.NestedScrollView>
<
/RelativeLayout>WebActivity.java
package example.srcmini.com.androidrssfeed;
import android.content.Context;
import android.content.Intent;
import android.graphics.Bitmap;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.text.TextUtils;
import android.webkit.WebChromeClient;
import android.webkit.WebResourceError;
import android.webkit.WebResourceRequest;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.Toast;
public class WebActivity extends AppCompatActivity {WebView webView;
String url;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_web);
Intent in = getIntent();
url = in.getStringExtra("url");
if (TextUtils.isEmpty(url)) {
Toast.makeText(getApplicationContext(), "URL not found", Toast.LENGTH_SHORT).show();
finish();
}
webView = findViewById(R.id.webView);
initWebView();
webView.loadUrl(url);
}private void initWebView() {
webView.setWebChromeClient(new MyWebChromeClient(this));
webView.clearCache(true);
webView.getSettings().setJavaScriptEnabled(true);
webView.setHorizontalScrollBarEnabled(false);
webView.setWebViewClient(new WebViewClient() {
@Override
public void onPageStarted(WebView view, String url, Bitmap favicon) {
super.onPageStarted(view, url, favicon);
}
@Override
public boolean shouldOverrideUrlLoading(WebView view, String url) {
webView.loadUrl(url);
return true;
}
@Override
public void onPageFinished(WebView view, String url) {
super.onPageFinished(view, url);
}
@Override
public void onReceivedError(WebView view, WebResourceRequest request, WebResourceError error) {
super.onReceivedError(view, request, error);
invalidateOptionsMenu();
}
});
webView.clearCache(true);
webView.clearHistory();
webView.getSettings().setJavaScriptEnabled(true);
webView.setHorizontalScrollBarEnabled(false);
}private class MyWebChromeClient extends WebChromeClient {
Context context;
public MyWebChromeClient(Context context) {
super();
this.context = context;
}
}
}需要权限
在AndroidMenifest.xml文件中添加INTERNET权限。
<
uses-permission android:name="android.permission.INTERNET" />输出：
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