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我試圖分析此：xml's url
通過下面這個教程Android XML Parsing Tutorial - Using SAXParser，我試圖修改源代碼，但我得到了一個錯誤：的Android，解析問題，以XML文件
11-17 20:04:38.072: I/System.out(13247): Error: null
11-17 20:04:38.072: D/AndroidRuntime(13247): Shutting down VM
11-17 20:04:38.082: W/dalvikvm(13247): threadid=1: thread exiting with uncaught exception (group=0x409951f8)
11-17 20:04:38.122: E/AndroidRuntime(13247): FATAL EXCEPTION: main
11-17 20:04:38.122: E/AndroidRuntime(13247): java.lang.RuntimeException: Unable to start activity ComponentInfo{net.net46.sourcecode.android.lectorxml2/net.net46.sourcecode.android.lectorxml2.LectorXML2Activity}: java.lang.NullPointerException
11-17 20:04:38.122: E/AndroidRuntime(13247): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1955)
11-17 20:04:38.122: E/AndroidRuntime(13247): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1980)
11-17 20:04:38.122: E/AndroidRuntime(13247): at android.app.ActivityThread.access$600(ActivityThread.java:122)
11-17 20:04:38.122: E/AndroidRuntime(13247): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1146)
11-17 20:04:38.122: E/AndroidRuntime(13247): at android.os.Handler.dispatchMessage(Handler.java:99)
11-17 20:04:38.122: E/AndroidRuntime(13247): at android.os.Looper.loop(Looper.java:137)
11-17 20:04:38.122: E/AndroidRuntime(13247): at android.app.ActivityThread.main(ActivityThread.java:4340)
11-17 20:04:38.122: E/AndroidRuntime(13247): at java.lang.reflect.Method.invokeNative(Native Method)
11-17 20:04:38.122: E/AndroidRuntime(13247): at java.lang.reflect.Method.invoke(Method.java:511)
11-17 20:04:38.122: E/AndroidRuntime(13247): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
11-17 20:04:38.122: E/AndroidRuntime(13247): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
11-17 20:04:38.122: E/AndroidRuntime(13247): at dalvik.system.NativeStart.main(Native Method)
11-17 20:04:38.122: E/AndroidRuntime(13247): Caused by: java.lang.NullPointerException
11-17 20:04:38.122: E/AndroidRuntime(13247): at net.net46.sourcecode.android.lectorxml2.LectorXML2Activity.onCreate(LectorXML2Activity.java:36)
11-17 20:04:38.122: E/AndroidRuntime(13247): at android.app.Activity.performCreate(Activity.java:4465)
11-17 20:04:38.122: E/AndroidRuntime(13247): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
11-17 20:04:38.122: E/AndroidRuntime(13247): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1919)
11-17 20:04:38.122: E/AndroidRuntime(13247): ... 11 more
那當模擬器運行時，我的LogCat。從原來的嘖嘖三個修改後的源代碼類現在：LectorXML2Activity.java，Lista.java，LecturaXML.java，下面的代碼：
//Lista.java
package net.net46.sourcecode.android.lectorxml2;
import java.util.ArrayList;
public class Lista {
private ArrayList<String> nombre = new ArrayList<String>();
private ArrayList<String> pagina = new ArrayList<String>();
private ArrayList<String> categoria = new ArrayList<String>();
public void setNombre(String nombre){
this.nombre.add(nombre);
}
public ArrayList<String> getNombre(){
return this.nombre;
}
public void setPagina(String pagina){
this.pagina.add(pagina);
}
public ArrayList<String> getPagina(){
return this.pagina;
}
public void setCategoria(String categoria){
this.categoria.add(categoria);
}
public ArrayList<String> getCategoria(){
return this.categoria;
}
}
//LecturaXML.java
package net.net46.sourcecode.android.lectorxml2;
import org.xml.sax.helpers.DefaultHandler;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
public class LecturaXML extends DefaultHandler{
public static Lista lista = null;
private Boolean elementoActual;
private String valorActual = null;
@Override
public void startElement(String uri, String nombreLocal,
String qNombre, Attributes atributos)
throws SAXException{
elementoActual = true;
if(nombreLocal.equals("tecnologias")){
lista = new Lista();
}else if(nombreLocal.equals("pagina")){
String attr = atributos.getValue("categoria");
lista.setCategoria(attr);
}
}
@Override
public void endElement(String uri, String nombreLocal, String qNombre)
throws SAXException{
elementoActual = false;
if(nombreLocal.equalsIgnoreCase("nombre")){
lista.setNombre(valorActual);
}else if(nombreLocal.equalsIgnoreCase("pagina")){
lista.setPagina(valorActual);
}
}
@Override
public void characters(char[]ch, int inicio, int longitud)
throws SAXException{
if(elementoActual){
valorActual = new String(ch,inicio,longitud);
elementoActual = false;
}
}
public static Lista getLista(){
return lista;
}
public static void setLista(Lista lista){
LecturaXML.lista = lista;
}
}
//LectorXML2Activity.java
package net.net46.sourcecode.android.lectorxml2;
import android.app.Activity;
import android.os.Bundle;
import android.widget.LinearLayout;
import android.widget.TextView;
import javax.xml.parsers.SAXParserFactory;
import javax.xml.parsers.SAXParser;
import net.net46.sourcecode.android.lectorxml2.R;
import org.xml.sax.XMLReader;
import org.xml.sax.InputSource;
import java.net.URL;
public class LectorXML2Activity extends Activity{
Lista lista = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
LinearLayout vista = new LinearLayout(this);
vista.setOrientation(1);
TextView[] nombre;
TextView[] pagina;
TextView[] categoria;
try{
SAXParserFactory spf = SAXParserFactory.newInstance();
SAXParser sp = spf.newSAXParser();
XMLReader xr = sp.getXMLReader();
URL url = new URL("http://sourcecode.net46.net/android/xml/tecnologies.xml");
LecturaXML lectura = new LecturaXML();
xr.setContentHandler(lectura);
xr.parse(new InputSource(url.openStream()));
}catch(Exception e){
System.out.println("Error: " + e.getMessage());
}
lista = LecturaXML.lista;
nombre = new TextView[lista.getNombre().size()];
pagina = new TextView[lista.getNombre().size()];
categoria = new TextView[lista.getNombre().size()];
for(int i=0;i<lista.getNombre().size();i++){
nombre[i] = new TextView(this);
nombre[i].setText("Nombre: "+lista.getNombre().get(i));
pagina[i] = new TextView(this);
pagina[i].setText("Pagina: "+lista.getPagina().get(i));
categoria[i] = new TextView(this);
categoria[i].setText("Categoría: "+lista.getCategoria().get(i));
vista.addView(nombre[i]);
vista.addView(pagina[i]);
vista.addView(categoria[i]);
}
setContentView(vista);
}
}
//AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="net.net46.sourcecode.android.lectorxml2"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk android:minSdkVersion="14" />
<application
android:icon="@drawable/ic_launcher"
android:label="@string/app_name" >
<activity
android:label="@string/app_name"
android:name=".LectorXML2Activity" >
<intent-filter >
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
<uses-permission android:name="android.permission.INTERNET"></uses-permission>
</manifest>
所以，我缺少什麼，使其正常？，如何工作我是否解決了NullPointerException問題？日Thnx提前..
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