java - 在 Android 中使用 SAX 解析 XML

Question

我有一个 XML 文件，如下所示:

<questions title="(Some question Category)">
 <question>
  <ask>(Some question)?</ask>
  <answer>(Some answer)</answer>
  <answer correct="true">(Some correct answer)</answer>
  <answer>(Some answer)</answer>
  <answer>(Some answer)</answer>
 </question>
</questions>

我正在使用 SAX 来解析该文件。据我所知，所有必需的 SAX 文件都已正确设置。

然后我有一个处理程序类，我查找了如何为稍微不同的 XML 文件编写代码。我尝试针对上面的 xml 进行调整，这是我想到的(未完成):

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URL;
import java.net.URLConnection;
import java.util.ArrayList;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
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 android.content.Context;
import android.graphics.Color;
import android.util.Log;
import android.widget.TextView;

public class QuestionHandler extends DefaultHandler {
    //list for imported product data
    private ArrayList<TextView> theViews;
    //string to track each entry
    private String currQuestion = "";
    //flags to keep track of XML processing
    private boolean isAsk = false;
    private boolean isAnswer = false;
    //context for user interface
    private Context theContext;
    //constructor
    public QuestionHandler(Context cont) {
        super();
        theViews = new ArrayList<TextView>();
        theContext = cont;
    }

    //start of the XML document
    public void startDocument () { Log.i("QuestionHandler", "Start of XML document"); }

    //end of the XML document
    public void endDocument () { Log.i("QuestionHandler", "End of XML document"); }

    //opening element tag
    public void startElement (String uri, String name, String qName, Attributes atts)
    {
        //find out if the element is a question
        if(qName.equals("question"))
        {
            //set ask and answer tag to false
            isAsk = false;
            isAnswer = false;
            //create View item for question display
            TextView questionView = new TextView(theContext);
            questionView.setTextColor(Color.rgb(73, 136, 83));
            //add the attribute value to the displayed text
            String viewText = "Items from " + atts.getValue("name") + ":";
            questionView.setText(viewText);
            //add the new view to the list
            theViews.add(questionView);
        }
        //or if the element is an asked question
        else if(qName.equals("ask"))
            isAsk = true;

        //or if element is an answer
        else if(qName.equals("answer"))
            isAnswer = true;
    }

    //closing element tag
    public void endElement (String uri, String name, String qName)
    {
        if(qName.equals("question"))
        {
            //create a View item for the asked
            TextView askView = new TextView(theContext);
            askView.setTextColor(Color.rgb(192, 199, 95));
            //display the compiled items
            askView.setText(currQuestion);
            //add to the list
            theViews.add(askView);
            //create a View item for the answers
            TextView answersView = new TextView(theContext);
            answersView.setTextColor(Color.rgb(192, 199, 95));
            //display the compiled items
            answersView.setText(currQuestion);
            //add to the list
            theViews.add(answersView);
            //reset the variable for future items
            currQuestion = "";
        }
    }

    //element content
    public void characters (char ch[], int start, int length)
    {
        //string to store the character content
        String currText = "";
        //loop through the character array
        for (int i=start; i<start+length; i++)
        {
            switch (ch[i]) {
            case '\\':
                break;
            case '"':
                break;
            case '\n':
                break;
            case '\r':
                break;
            case '\t':
                break;
            default:
                currText += ch[i];
                break;
            }
        }
        //prepare for the next item
        if(isAsk || isAnswer && currText.length()>0)
            currQuestion += currText+"\n";
    }
    public ArrayList<TextView> getData()
    {
        //take care of SAX, input and parsing errors
        try
        {
            //set the parsing driver
            System.setProperty("org.xml.sax.driver","org.xmlpull.v1.sax2.Driver");
            //create a parser
            SAXParserFactory parseFactory = SAXParserFactory.newInstance();
            SAXParser xmlParser = parseFactory.newSAXParser();
            //get an XML reader
            XMLReader xmlIn = xmlParser.getXMLReader();
            //instruct the app to use this object as the handler
            xmlIn.setContentHandler(this);
            //provide the name and location of the XML file **ALTER THIS FOR YOUR FILE**
            URL xmlURL = new URL("http://www.macs.hw.ac.uk/~pjbk/quiz/example.xml");
            //open the connection and get an input stream
            URLConnection xmlConn = xmlURL.openConnection();
            InputStreamReader xmlStream = new InputStreamReader(xmlConn.getInputStream());
            //build a buffered reader
            BufferedReader xmlBuff = new BufferedReader(xmlStream);
            //parse the data
            xmlIn.parse(new InputSource(xmlBuff));
        }
        catch(SAXException se) { Log.e("AndroidTestsActivity", 
                "SAX Error " + se.getMessage()); }
        catch(IOException ie) { Log.e("AndroidTestsActivity", 
                "Input Error " + ie.getMessage()); }
        catch(Exception oe) { Log.e("AndroidTestsActivity", 
                "Unspecified Error " + oe.getMessage()); }
        //return the parsed product list
        return theViews;
    }

}

最后，我的initialiseQuestions() 方法(来自其他工作 Activity )将提取的XML 数据分配给问题类(同样，未完成):

private void initialiseQuestions() {
    // TODO Auto-generated method stub

    questions = new Vector<Question>(); //Vector containing our questions

    try
    {
        //create an instance of the QuestionHandler class
        QuestionHandler handler = new QuestionHandler(getApplicationContext());
        //get the string list by calling the public method
        ArrayList<TextView> newViews = handler.getData();
        //convert to an array
        Object[] question = newViews.toArray();
        //loop through the items, creating a View item for each
        for(int i=0; i<question.length; i++)
        {
            //add the next question in the list
            Question q1 = new Question(question[i]);
            q1.addAnswer("Harold Godwin", false);
            q1.addAnswer("Edward the Confessor", false);
            q1.addAnswer("William the Conqueror", true);
            q1.addAnswer("Alfred the Great", false);
            questions.add(q1);
            //mainLayout.addView((TextView)products[i]);
        }

    }
    catch(Exception pce) { Log.e("AndroidTestsActivity", "PCE "+pce.getMessage()); }

我的主要问题是我不太明白我在做什么/需要在处理程序和initialiseQuestions 方法中进行更改。我不明白如何在处理程序中创建字符串(如果您只需要发回一个字符串数组，为什么需要 textViews？)并且我不明白如何在initialiseQuestions 中处理回数据。正如您所看到的， initaliseQuestions 方法应该采用解析后的 XML 并使用数据实例化一个问题对象。

有人可以告诉我我需要改变什么吗？

Here's the tutorial我一直在努力调整

Answer 1

解析 XML 确实是一项整洁的工作。有一个很好的图书馆Simple XML ，我们可以在Android中轻松使用。它是基于注释的库，有很好的教程。最好的事情是它直接从 XML 返回 POJO，并且在性能方面，它很好。

您所需要做的就是为您的 XML 创建一个基于注释的 POJO(请参阅网站上的教程)。使用 serializer.read(pojoClassType, xmlStr) 获取 POJO 的对象。

您还可以使用 Java 泛型概念仅使用一种通用方法来读取每个 XML 文件。就像，

public <T> T parseXML(Class<T> pojoType, String xmlStr){
 //your code
}