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我試圖解析來自服務器的XML文件，我與此tutorial同仁，但我無法在Logcat中的活動中檢索數據！
它顯示了在這一行
for(int i = 0; i < data.getTitle().size(); i++) 根據該教程，我不知道如果我intialised變量數據正確的活動一個NullPointerException。 所以這是我MainActivity：無法使用SAX解析器檢索數據
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity {
TextView title[];
TextView artist[];
TextView country[];
TextView company[];
TextView price[];
TextView year[];
public static XMLGettersSetters data ;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
View layout = findViewById(R.id.layout);
for (int i = 0; i < data.getTitle().size(); i++) {
title[i] = new TextView(this);
title[i].setText("Title= " + data.getTitle().get(i));
artist[i] = new TextView(this);
artist[i].setText("Artist=" + data.getArtist().get(i));
company[i] = new TextView(this);
company[i].setText("Company=" + data.getCompany().get(i));
country[i] = new TextView(this);
country[i].setText("Country=" + data.getCountry().get(i));
price[i] = new TextView(this);
price[i].setText("Price=" + data.getPrice().get(i));
year[i] = new TextView(this);
year[i].setText("Year=" + data.getYear().get(i));
((ViewGroup) layout).addView(title[i]);
((ViewGroup) layout).addView(artist[i]);
((ViewGroup) layout).addView(company[i]);
((ViewGroup) layout).addView(country[i]);
((ViewGroup) layout).addView(price[i]);
((ViewGroup) layout).addView(year[i]);
}
}
}
XMLHandler類
import org.xml.sax.Attributes;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.DefaultHandler;
import java.net.URL;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
public class XMLHandler extends DefaultHandler {
String elementValue = null;
Boolean elementOn = false;
public static XMLGettersSetters data = null;
public static XMLGettersSetters getXMLData() {
return data;
}
public static void setXMLData(XMLGettersSetters data) {
XMLHandler.data = data;
}
/**
* This will be called when the tags of the XML starts.
**/
@Override
public void startElement(String uri, String localName, String qName,
Attributes attributes) throws SAXException {
elementOn = true;
if (localName.equals("CATALOG")) {
data = new XMLGettersSetters();
} else if (localName.equals("CD")) {
/**
* We can get the values of attributes for eg. if the CD tag had an attribute(<CD attr= "band">Akon</CD>)
* we can get the value "band". Below is an example of how to achieve this.
*
* String attributeValue = attributes.getValue("attr");
* data.setAttribute(attributeValue);
*
* */
try {
/**
* Create a new instance of the SAX parser
**/
SAXParserFactory saxPF = SAXParserFactory.newInstance();
SAXParser saxP = saxPF.newSAXParser();
XMLReader xmlR = saxP.getXMLReader();
URL url = new URL("http://www.xmlfiles.com/examples/cd_catalog.xml"); // URL of the XML
/**
* Create the Handler to handle each of the XML tags.
**/
XMLHandler myXMLHandler = new XMLHandler();
xmlR.setContentHandler(myXMLHandler);
xmlR.parse(new InputSource(url.openStream()));
// View layout = findViewById(R.id.layout);
} catch (Exception e) {
System.out.println(e);
}
}
}
/**
* This will be called when the tags of the XML end.
**/
@Override
public void endElement(String uri, String localName, String qName)
throws SAXException {
elementOn = false;
/**
* Sets the values after retrieving the values from the XML tags
* */
if (localName.equalsIgnoreCase("title"))
data.setTitle(elementValue);
else if (localName.equalsIgnoreCase("artist"))
data.setArtist(elementValue);
else if (localName.equalsIgnoreCase("country"))
data.setCountry(elementValue);
else if (localName.equalsIgnoreCase("company"))
data.setCompany(elementValue);
else if (localName.equalsIgnoreCase("price"))
data.setPrice(elementValue);
else if (localName.equalsIgnoreCase("year"))
data.setYear(elementValue);
}
/**
* This is called to get the tags value
**/
@Override
public void characters(char[] ch, int start, int length)
throws SAXException {
if (elementOn) {
elementValue = new String(ch, start, length);
elementOn = false;
}
}
}
XmlGettersSetters
import android.util.Log;
import java.util.ArrayList;
public class XMLGettersSetters {
//company
private ArrayList<String> company = new ArrayList<String>();
public ArrayList<String> getCompany() {
return company;
}
public void setCompany(String company) {
this.company.add(company);
Log.i("This is the company:", company);
}
//title
private ArrayList<String> title = new ArrayList<String>();
public ArrayList<String> getTitle() {
return title;
}
public void setTitle(String title) {
this.title.add(title);
Log.i("This is the title:", title);
}
//artist
private ArrayList<String> artist = new ArrayList<String>();
public ArrayList<String> getArtist() {
return artist;
}
public void setArtist(String artist) {
this.artist.add(artist);
Log.i("This is the artist:", artist);
}
//country
private ArrayList<String> country = new ArrayList<String>();
public ArrayList<String> getCountry() {
return country;
}
public void setCountry(String country) {
this.country.add(country);
Log.i("This is the country:", country);
}
//price
private ArrayList<String> price = new ArrayList<String>();
public ArrayList<String> getPrice() {
return price;
}
public void setPrice(String price) {
this.price.add(price);
Log.i("This is the price:", price);
}
//year
private ArrayList<String> year = new ArrayList<String>();
public ArrayList<String> getYear() {
return year;
}
public void setYear(String year) {
this.year.add(year);
Log.i("This is the Year:", year);
}
}