我正在开发一个使用 SAX 解析器进行 XML 解析的 android 应用程序。我的 XML 目前在我的 WAMP 服务器上。在我的应用程序中，当我点击一个按钮时，我会看到一个标题列表，而在选择一个标题时，我会看到它的详细信息。我的问题是我的应用程序崩溃了。我搜索了很多，但找不到任何解决方案。当我从本地文件中获取我的 XML 数据时，它可以工作，但是当我从 URL 中获取它时，它会崩溃。我希望你能帮助我一些事情。
这是我的日志猫。
07-13 17:30:14.874: E/AndroidRuntime(6844): FATAL EXCEPTION: main
07-13 17:30:14.874: E/AndroidRuntime(6844): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.svnitupdates/com.example.svnitupdates.UpdatesActivity}: java.lang.NullPointerException
07-13 17:30:14.874: E/AndroidRuntime(6844): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
07-13 17:30:14.874: E/AndroidRuntime(6844): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
07-13 17:30:14.874: E/AndroidRuntime(6844): at android.app.ActivityThread.access$600(ActivityThread.java:141)
07-13 17:30:14.874: E/AndroidRuntime(6844): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
07-13 17:30:14.874: E/AndroidRuntime(6844): at android.os.Handler.dispatchMessage(Handler.java:99)
07-13 17:30:14.874: E/AndroidRuntime(6844): at android.os.Looper.loop(Looper.java:137)
07-13 17:30:14.874: E/AndroidRuntime(6844): at android.app.ActivityThread.main(ActivityThread.java:5041)
07-13 17:30:14.874: E/AndroidRuntime(6844): at java.lang.reflect.Method.invokeNative(Native Method)
07-13 17:30:14.874: E/AndroidRuntime(6844): at java.lang.reflect.Method.invoke(Method.java:511)
07-13 17:30:14.874: E/AndroidRuntime(6844): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
07-13 17:30:14.874: E/AndroidRuntime(6844): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
07-13 17:30:14.874: E/AndroidRuntime(6844): at dalvik.system.NativeStart.main(Native Method)
07-13 17:30:14.874: E/AndroidRuntime(6844): Caused by: java.lang.NullPointerException
07-13 17:30:14.874: E/AndroidRuntime(6844): at com.example.svnitupdates.UpdatesActivity.onCreate(UpdatesActivity.java:66)
07-13 17:30:14.874: E/AndroidRuntime(6844): at android.app.Activity.performCreate(Activity.java:5104)
07-13 17:30:14.874: E/AndroidRuntime(6844): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
07-13 17:30:14.874: E/AndroidRuntime(6844): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
07-13 17:30:14.874: E/AndroidRuntime(6844): ... 11 more
这是我的更新活动。
package com.example.svnitupdates;
import java.net.URL;
import java.util.ArrayList;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import org.xml.sax.InputSource;
import org.xml.sax.XMLReader;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListView;
public class UpdatesActivity extends Activity
{
private ListView listview;
NewsList newsList = null;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.updates);
listview = (ListView) findViewById(R.id.updatesListView);
final ArrayList<String> list = new ArrayList<String>();
try {
/** Handling XML */
SAXParserFactory spf = SAXParserFactory.newInstance();
SAXParser sp = spf.newSAXParser();
XMLReader xr = sp.getXMLReader();
/** Send URL to parse XML Tags */
URL sourceUrl = new URL ("http://localhost/My%20files/data.xml");
/** Create handler to handle XML Tags ( extends DefaultHandler ) */
MyXMLHandler myXMLHandler = new MyXMLHandler();
xr.setContentHandler( myXMLHandler);
xr.parse(new InputSource(sourceUrl.openStream()));
//xr.parse(new InputSource(is.getByteStream()));
} catch (Exception e) {
System.out.println("XML Parsing Excpetion = " + e);
}
newsList = MyXMLHandler.newsList;
for (int i = 0; i < newsList.getTitle().size(); i++)
{
list.add(newsList.getTitle().get(i));
}
final UpdatesAdapter adapter = new UpdatesAdapter(UpdatesActivity.this , android.R.layout.simple_list_item_1, list);
listview.setAdapter(adapter);
listview.setItemsCanFocus(false);
listview.setOnItemClickListener(new AdapterView.OnItemClickListener()
{
public void onItemClick(AdapterView<?> parent, View view,int position, long id)
{
Intent i = new Intent(UpdatesActivity.this, ArticleActivity.class);
i.putExtra("s", position);
startActivity(i);
}
});
}
}
这是我的 XMLHandler 类。
package com.example.svnitupdates;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;
public class MyXMLHandler extends DefaultHandler{
Boolean currentElement = false;
String currentValue = null;
public static NewsList newsList = null;
public static NewsList getNewsList() {
return newsList;
}
public static void setNewsList(NewsList newsList) {
MyXMLHandler.newsList = newsList;
}
/** Called when tag starts ( ex:- <name>AndroidPeople</name>
* -- <name> )*/
public void startElement(String uri, String localName, String qName,
Attributes attributes) throws SAXException {
currentElement = true;
if (localName.equals("maintag"))
{
/** Start */
newsList = new NewsList();
}
}
/** Called when tag closing ( ex:- <name>AndroidPeople</name>
* -- </name> )*/
public void endElement(String uri, String localName, String qName)
throws SAXException {
currentElement = false;
/** set value */
if (localName.equalsIgnoreCase("title"))
newsList.setTitle(currentValue);
}
/** Called to get tag characters ( ex:- <name>AndroidPeople</name>
* -- to get AndroidPeople Character ) */
public void characters(char[] ch, int start, int length)
throws SAXException {
if (currentElement) {
currentValue = new String(ch, start, length);
currentElement = false;
}
}
}
这是我的新闻列表类。
package com.example.svnitupdates;
import java.util.ArrayList;
public class NewsList {
/** Variables */
private ArrayList<String> title = new ArrayList<String>();
//private ArrayList<String> news = new ArrayList<String>();
/** In Setter method default it will return arraylist
* change that to add */
public ArrayList<String> getTitle() {
return title;
}
public void setTitle(String title) {
this.title.add(title);
}
public ArrayList<String> getNews() {
return title;
}
public void setNews(String title) {
this.title.add(title);
}
public ArrayList<String> getChp() {
return title;
}
public void setChp(String title) {
this.title.add(title);
}
public ArrayList<String> getContacts() {
return title;
}
public void setContacts(String title) {
this.title.add(title);
}
}
这是我的文章活动。
package com.example.svnitupdates;
import java.net.URL;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import org.xml.sax.InputSource;
import org.xml.sax.XMLReader;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.widget.TextView;
public class ArticleActivity extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_article);
Intent i = getIntent();
savedInstanceState = i.getExtras();
int k = savedInstanceState.getInt("s");
updateArticleView(k);
}
public void updateArticleView(int position) {
NewsList newslist = null;
try {
/** Handling XML */
SAXParserFactory spf = SAXParserFactory.newInstance();
SAXParser sp = spf.newSAXParser();
XMLReader xr = sp.getXMLReader();
/** Send URL to parse XML Tags */
URL sourceUrl = new URL ("http://localhost/My%20files/data.xml");
/** Create handler to handle XML Tags ( extends DefaultHandler ) */
MyXMLHandlerArticle myXMLHandler = new MyXMLHandlerArticle();
xr.setContentHandler(myXMLHandler);
xr.parse(new InputSource(sourceUrl.openStream()));
} catch (Exception e) {
System.out.println("XML Parsing Excpetion = " + e);
}
newslist = MyXMLHandlerArticle.newsList;
TextView textView = (TextView) findViewById(R.id.textView1);
textView.setText(newslist.getNews().get(position));
}
}
我的 XML 文件在这里。
<maintag>
<item>
<title>1st round interview of Student Council on 2nd April</title>
<news>Student Council interviews on 2nd April. Students are requested to be on time. 1st round of interviews will be held in th Seminar Hall of respective department</news>
</item>
<item>
<title>Interviews for 1st yearites for Drishti on 2nd April</title>
<news>Interviews for drishti are being held on next monday. Those interested be present at sharp 5:00 PM at drishti room</news>
</item>
<item>
<title>Workshop on Basic GUI Development by ACM on 3rd and 4th April</title>
<news>Acm workshop on basic GUI. Those interested register on the link http://bit.ly/1073SMx. Install the required software from the link provided. Bring your laptops along(max 3 people/laptop).</news>
</item>
<item>
<title>Registration for Treasure Hunt by CES starting from 5th April</title>
<news>Registration for treasure hunt starting from 5th april. Prizes worth 15,000/- can be won.Do register and win.</news>
</item>
</maintag>