Pull解析

首先获取到一个XmlPullParserFactory的实例，再调用setInput()方法将xml数据返回到当前的事件。通过getEventtype()方法可以得到当前的解析事件

XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
XmlPullParser xmlPullParser = factory.newPullParser();
xmlPullParser.setInput(new StringReader(xmlData));
int eventType = xmlPullParser.getEventType();

再在while循环中不断解析，如果当前事件不等于XmlPullParser.END_DOCUMENT,说明解析没有完成，调用next()方法后可以获取下一个解析事件，在循环中，用getName来获取当前节点的名字,然后调用nextText()方法获得节点内容。
这里有一份准备好的数据文件。

while (eventType!=XmlPullParser.END_DOCUMENT){
    String nodeName = xmlPullParser.getName();
    switch (eventType){
    //开始解析节点
        case XmlPullParser.START_TAG:{
            if("id".equals(nodeName)){
                id = xmlPullParser.nextText();
            }else if("name".equals(nodeName)){
                name = xmlPullParser.nextText();
            }else if("version".equals(nodeName)){
                version = xmlPullParser.nextText();
            }
            break;
        }
        case XmlPullParser.END_TAG:{
            if("app".equals(nodeName)){
                Log.d("id",id);
                Log.d("name",name);
                Log.d("version",version);
            }
            break;
        }
    }
    eventType = xmlPullParser.next();
}

SAX解析

SAX用法比Pull要复杂一些，但是语义方面会更加清楚。通常情况下新建一个类并且继承DefaultHandler，并重写父类的5个方法

public class MyHandler extends DefaultHandler {
    private String nodeName;
    private StringBuilder id;
    private StringBuilder name;
    private StringBuilder version;

    //开始XML解析时调用
    @Override
    public void startDocument() throws SAXException {
        id = new StringBuilder();
        name = new StringBuilder();
        version = new StringBuilder();
    }

    //开始解析某个节点时调用
    @Override
    public void startElement(String uri,String localName,String qName,Attributes 
        attributes) throws SAXException {
        nodeName = localName;
    }

    //获取节点内容时调用
    @Override
    public void characters(char[] ch,int start,int length) throws SAXException {
        if("id".equals(nodeName)){
            id.append(ch,start,length);
        }else if("name".equals(nodeName)){
            name.append(ch,length);
        }else if("version".equals(nodeName)){
            version.append(ch,length);
        }
    }

    //完成解析某个节点时调用
    @Override
    public void endElement(String uri,String qName) throws 
        SAXException {
        if("app".equals(nodeName)){
            Log.d("id",id.toString().trim());
            Log.d("name",name.toString().trim());
            Log.d("version",version.toString().trim());
            //清空StringBuilder
            id.setLength(0);
            name.setLength(0);
            version.setLength(0);
        }
    }

    //完成解析XML时调用
    @Override
    public void endDocument() throws SAXException {
        super.endDocument();
    }
}

接下来的工作和Pull差不多

SAXParserFactory factory = SAXParserFactory.newInstance();
XMLReader xmlReader = factory.newSAXParser().getXMLReader();
MyHandler handler = new MyHandler();
xmlReader.setContentHandler(handler);
//开始执行解析
xmlReader.parse(new InputSource(new StringReader(xmlData)));