1.SAX概念
SXA：Simple API for XML
基于事件驱动（Android中的事件驱动基于回调函数），边加载边解析。
五个主要的回调方法：
startDocument（） //处理文档解析开始事件
startElement（）
//处理元素开始事件
endElement（）
//处理元素结束事件
endDocument（）
//处理文档结束事件
2.基本步骤
（1）创建SAXParserFactory对象（newInstance()）
（2）根据SAXParserFactory对象的newSAXParser()方法创建SAXParser解析器对象
（3）根据SAXParser解析器对象获得事件源对象XMLReader对象
（4）实例化一个DefaultHandler对象
（5）连接事件源对象到事件处理器DefaultHandler中（setContentHandler方法）
（6）使用XMLReader的parse方法解析从输入源中获取的XML数据
（7）通过DefaultHandler返回需要的数据集合
3.实例
需要解析的xml文档
<?xml version="1.0" encoding="utf-8"?> <students> <student id="0"> <name>zhangmq</name> <gender>female</gender> <age>24</age> </student> <student id="1"> <name>zhouhy</name> <gender>male</gender> <age>24</age> </student> </students>
根据xml文档定义的Student类
public class Student {
private String id;
private String name;
private String gender;
private String age;
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getGender() {
return gender;
}
public void setGender(String gender) {
this.gender = gender;
}
public String getAge() {
return age;
}
public void setAge(String age) {
this.age = age;
}
public String toString(){
return "Student [id = "+id+" name = "+name +" gender = "+gender+" age = "+age+"]";
}
}
具体解析代码
public class SAXParseHandler extends DefaultHandler {
List<Student> students;
Student student;
String nodeName; //记录当前的元素名字
// 处理文档解析开始事件
@Override
public void startDocument() throws SAXException {
// TODO Auto-generated method stub
Log.d("zhangmq","startDocument");
students = new ArrayList<Student>();
}
// 处理元素解析开始事件
@Override
public void startElement(String uri,String localName,String qName,Attributes attributes) throws SAXException {
// TODO Auto-generated method stub
Log.d("zhangmq","startElement");
Log.d("zhangmq","startElement localName = " + localName);
Log.d("zhangmq","startElement qName = " + qName);
Log.d("zhangmq","startElement attributes.getLength() = "
+ attributes.getLength());
if (localName.equals("student")) {
student = new Student();
for (int i = 0; i < attributes.getLength(); i++) {
if (attributes.getLocalName(i).equals("id")) {
student.setId(attributes.getValue(i));
}
}
} else {
nodeName = localName;
}
}
// 接收字符块通知
@Override
public void characters(char[] ch,int start,int length)
throws SAXException {
// TODO Auto-generated method stub
Log.d("zhangmq","characters");
Log.d("zhangmq","characters ch = " + ch);
Log.d("zhangmq","characters start = " + start);
Log.d("zhangmq","characters length = " + length);
//这个地方比较容易失误
//若是不加trim，则str可能是一个空字符串，但它不是普通的null或是""，而是" ".
//这样会导致判断str != null && !"".equals(str)的时候失误。千万要注意.
//要判断str是因为还会解析</name>,得到的nodeName跟<name>是一样的.
String str = String.valueOf(ch,start,length).trim();
Log.d("zhangmq","characters str = " + str);
Log.d("zhangmq","characters nodeName = " + nodeName);
if (str != null && !"".equals(str)) {
if ("name".equals(nodeName)) {
student.setName(str);
} else if ("gender".equals(nodeName)) {
student.setGender(str);
} else if ("age".equals(nodeName)) {
student.setAge(str);
}
}
}
// 接收元素结束通知
@Override
public void endElement(String uri,String qName)
throws SAXException {
// TODO Auto-generated method stub
Log.d("zhangmq","endElement");
// 判断标签是否为student
if (localName.equals("student")) {
students.add(student);
}
}
// 接收文档结束通知
@Override
public void endDocument() throws SAXException {
// TODO Auto-generated method stub
super.endDocument();
Log.d("zhangmq","endDocument");
}
public String getStudentsString() {
// 再需要+字符串时，str最好定义成"",否则，在显示字符串的时候最前面的是null,例如下面的就是：nullStudent
String str = "";
for (int i = 0; i < students.size(); i++) {
str = str + students.get(i).toString() + "\n";
}
return str;
}
}
解析xml文档
public class SaxParseActivity extends Activity {
private TextView sax_parse_tv;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_sax);
sax_parse_tv = (TextView) findViewById(R.id.sax_parse);
sax_parse_tv.setText(saxParseXml());
}
private String saxParseXml() {
String str = null;
SAXParserFactory factory = null;
//解析器对象
SAXParser parse = null;
//事件源对象
XMLReader reader = null;
InputStream is = null;
//SAX解析的帮助类，继承DefaultHandler
SAXParseHandler parseHandler = null;
//1.实例化SAXParserFactory对象
factory = SAXParserFactory.newInstance();
try {
//2.使用SAXParserFactory对象实例化SAXParser对象
parse = factory.newSAXParser();
} catch (ParserConfigurationException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SAXException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
//3.使用SAXParser对象实例化XMLReader
reader = parse.getXMLReader();
} catch (SAXException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
//自己写的SAX解析帮助类，实例化
parseHandler = new SAXParseHandler();
//解析器注册事件
reader.setContentHandler(parseHandler);
try {
//获取xml文件到输入流中
is = getResources().getAssets().open("dom_info.xml");
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
InputSource inputSource = new InputSource(is);
try {
//解析文件，事件源
reader.parse(inputSource);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SAXException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
str = parseHandler.getStudentsString();
return str;
}
}