0
我按照教程here發現了一個NullPointerException異常。我在StackOverflow和Google上搜索了一個可能的解決方案，但無濟於事。下面你會看到我的代碼和我的LogCat。有關我應該如何解決此問題的任何想法？解析XML時出現NullPointerException
XMLParsingExample.java（57行=其中的NullPointerException發生）：
package com.androidpeople.xml.parsing;
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.os.Bundle;
import android.widget.LinearLayout;
import android.widget.TextView;
public class XMLParsingExample extends Activity {
/** Create Object For SiteList Class */
SitesList sitesList = null;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
/** Create a new layout to display the view */
LinearLayout layout = new LinearLayout(this);
layout.setOrientation(1);
/** Create a new textview array to display the results */
TextView name[];
TextView website[];
TextView category[];
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://www.androidpeople.com/wp-content/uploads/2010/06/example.xml");
/** Create handler to handle XML Tags (extends DefaultHandler) */
MyXMLHandler myXMLHandler = new MyXMLHandler();
xr.setContentHandler(myXMLHandler);
xr.parse(new InputSource(sourceUrl.openStream()));
} catch (Exception e) {
System.out.println("XML Pasing Excpetion = " + e);
}
/** Get result from MyXMLHandler SitlesList Object */
sitesList = MyXMLHandler.sitesList;
/** Assign textview array length by arraylist size */
name = new TextView[sitesList.getName().size()]; //NullPointerException Here
website = new TextView[sitesList.getName().size()];
category = new TextView[sitesList.getName().size()];
/** Set the result text in textview and add it to layout */
for (int i = 0; i < sitesList.getName().size(); i++) {
name[i] = new TextView(this);
name[i].setText("Name = "+sitesList.getName().get(i));
website[i] = new TextView(this);
website[i].setText("Website = "+sitesList.getWebsite().get(i));
category[i] = new TextView(this);
category[i].setText("Website Category = "+sitesList.getCategory().get(i));
layout.addView(name[i]);
layout.addView(website[i]);
layout.addView(category[i]);
}
/** Set the layout view to display */
setContentView(layout);
}
}
MyXMLHandler.java：
package com.androidpeople.xml.parsing;
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 SitesList sitesList = null;
public static SitesList getSitesList() {
return sitesList;
}
public static void setSitesList(SitesList sitesList) {
MyXMLHandler.sitesList = sitesList;
}
/** Called when tag starts (ex:- <name>AndroidPeople</name>
* -- <name>)*/
@Override
public void startElement(String uri, String localName, String qName,
Attributes attributes) throws SAXException {
currentElement = true;
if (localName.equals("maintag"))
{
/** Start */
sitesList = new SitesList();
} else if (localName.equals("website")) {
/** Get attribute value */
String attr = attributes.getValue("category");
sitesList.setCategory(attr);
}
}
/** Called when tag closing (ex:- <name>AndroidPeople</name>
* -- </name>)*/
@Override
public void endElement(String uri, String localName, String qName)
throws SAXException {
currentElement = false;
/** set value */
if (localName.equalsIgnoreCase("name"))
sitesList.setName(currentValue);
else if (localName.equalsIgnoreCase("website"))
sitesList.setWebsite(currentValue);
}
/** Called to get tag characters (ex:- <name>AndroidPeople</name>
* -- to get AndroidPeople Character) */
@Override
public void characters(char[] ch, int start, int length)
throws SAXException {
if (currentElement) {
currentValue = new String(ch, start, length);
currentElement = false;
}
}
}
SitesList.java：
package com.androidpeople.xml.parsing;
import java.util.ArrayList;
/** Contains getter and setter method for varialbles */
public class SitesList {
/** Variables */
private ArrayList<String> name = new ArrayList<String>();
private ArrayList<String> website = new ArrayList<String>();
private ArrayList<String> category = new ArrayList<String>();
/** In Setter method default it will return arraylist
* change that to add */
public ArrayList<String> getName() {
return name;
}
public void setName(String name) {
this.name.add(name);
}
public ArrayList<String> getWebsite() {
return website;
}
public void setWebsite(String website) {
this.website.add(website);
}
public ArrayList<String> getCategory() {
return category;
}
public void setCategory(String category) {
this.category.add(category);
}
}
AndroidParsing清單：
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.androidpeople.xml.parsing"
android:versionCode="1"
android:versionName="1.0">
<uses-sdk android:minSdkVersion="8" />
<application android:icon="@drawable/icon" android:label="@string/app_name">
<activity android:name=".XMLParsingExample"
android:label="@string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".MyXMLHandler"></activity>
<activity android:name=".SitesList"></activity>
</application>
<uses-permission android:name="android.permission.INTERNET"></uses-permission>
</manifest>
的logcat：
08-22 08:43:18.340: ERROR/AndroidRuntime(308): FATAL EXCEPTION: main
08-22 08:43:18.340: ERROR/AndroidRuntime(308): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.androidpeople.xml.parsing/com.androidpeople.xml.parsing.XMLParsingExample}: java.lang.NullPointerException
08-22 08:43:18.340: ERROR/AndroidRuntime(308): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
08-22 08:43:18.340: ERROR/AndroidRuntime(308): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
08-22 08:43:18.340: ERROR/AndroidRuntime(308): at android.app.ActivityThread.access$2300(ActivityThread.java:125)
08-22 08:43:18.340: ERROR/AndroidRuntime(308): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
08-22 08:43:18.340: ERROR/AndroidRuntime(308): at android.os.Handler.dispatchMessage(Handler.java:99)
08-22 08:43:18.340: ERROR/AndroidRuntime(308): at android.os.Looper.loop(Looper.java:123)
08-22 08:43:18.340: ERROR/AndroidRuntime(308): at android.app.ActivityThread.main(ActivityThread.java:4627)
08-22 08:43:18.340: ERROR/AndroidRuntime(308): at java.lang.reflect.Method.invokeNative(Native Method)
08-22 08:43:18.340: ERROR/AndroidRuntime(308): at java.lang.reflect.Method.invoke(Method.java:521)
08-22 08:43:18.340: ERROR/AndroidRuntime(308): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
08-22 08:43:18.340: ERROR/AndroidRuntime(308): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
08-22 08:43:18.340: ERROR/AndroidRuntime(308): at dalvik.system.NativeStart.main(Native Method)
08-22 08:43:18.340: ERROR/AndroidRuntime(308): Caused by: java.lang.NullPointerException
08-22 08:43:18.340: ERROR/AndroidRuntime(308): at com.androidpeople.xml.parsing.XMLParsingExample.onCreate(XMLParsingExample.java:57)
08-22 08:43:18.340: ERROR/AndroidRuntime(308): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
08-22 08:43:18.340: ERROR/AndroidRuntime(308): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
這有點令人困惑。它並不告訴我哪裏可以放入第一個代碼片段的代碼。 – Mxyk
我認爲你需要完整的源代碼...它是否正確。如果你想我會給出完整的例子，解析爲該網址。 – harish
如果可以的話，那會很棒。 – Mxyk