3-SIII-Android数据固化之Xml的Sax解析和存储

Sax解析方式会逐行地去扫描XML文档，当遇到标签时会触发解析处理器，采用事件处理的方式解析XML 
优点：在读取文档的同时即可对XML进行处理，不必等到文档加载结束，相对快捷,所以可以解析超大XML
缺点：只能用来读取XML中数据，无法进行增删改。

<?xml version="1.0" encoding="UTF-8"?>
<weapons>
    <weapon material="玉" type="剑">
        <name>问天剑</name>
        <atk>2000</atk>
        <user>语熙华</user>
    </weapon>
    <weapon material="铁" type="刀">
        <name>皇刀</name>
        <atk>3000</atk>
        <user>九方玄玉</user>
    </weapon>
</weapons>

/**
 * 
 * @return
 */
private ArrayList<WeaponXml> parseXmlWithSax() {
    InputStream is = null;
    mWeapons = new ArrayList<>();
    try {
        SAXParser saxParser = SAXParserFactory.newInstance().newSAXParser();
        is = getAssets().open("weapon.xml");
        saxParser.parse(is, new DefaultHandler() {
            /**
             *  开始标签时
             * @param uri 命名空间
             * @param localName 标签名
             * @param qName 全名(带命名空间的标签的名字)
             * @param attributes 属性
             * @throws SAXException
             */
            @Override
            public void startElement(String uri, String localName,
                                     String qName, Attributes attributes) throws SAXException {
                //"属性名：" + attributes.getLocalName(i)
                //"属性值：" + attributes.getValue(i));
                if ("weapon".equals(localName)) {
                    mWeapon = new WeaponXml();
                    mWeapon.setMaterial(attributes.getValue(0));
                    mWeapon.setType(attributes.getValue(1));
                }
                mPerTag = localName;
            }
            /**解析标签的内容的时候调用
             *
             * @param ch 当前文本节点的字节数组
             * @param start 字节开始的位置 默认 0 全部读取
             * @param length 长度
             * @throws SAXException
             */
            @Override
            public void characters(char[] ch, int start, int length) throws SAXException {
                String chars = new String(ch, start, length).trim();
                if ("name".equals(mPerTag)) {
                    mWeapon.setName(chars);
                } else if ("atk".equals(mPerTag)) {
                    mWeapon.setAtk(Integer.parseInt(chars));
                } else if ("user".equals(mPerTag)) {
                    mWeapon.setUser(chars);
                }
            }
            /**
             * 标签解析结束调用
             * @param uri
             * @param localName
             * @param qName
             * @throws SAXException
             */
            @Override
            public void endElement(String uri, String localName, String qName) throws SAXException {
                if ("weapon".equals(localName)) {
                    mWeapons.add(mWeapon);
                    mWeapon = null;
                }
                mPerTag = null;
            }
        });
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        if (is != null) {
            try {
                is.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
    return mWeapons;
}

/**
 * sax创建Xml文件
 */
private void saxCreateXml() {
    ArrayList<WeaponXml> weaponXmls = parseXmlWithSax();
    //1、创建一个SAXTransformerFactory的对象
    SAXTransformerFactory saxTF = (SAXTransformerFactory) SAXTransformerFactory.newInstance();
    FileOutputStream fos = null;
    try {
        //创建一个Transformer对象
        TransformerHandler handler = saxTF.newTransformerHandler();
        Transformer transformer = handler.getTransformer();
        transformer.setOutputProperty(OutputKeys.ENCODING, "utf-8");
        transformer.setOutputProperty(OutputKeys.INDENT, "yes");
        String path = Environment.getExternalStorageDirectory().getAbsolutePath();
        fos = new FileOutputStream(path + File.separator + "weaponSax.xml");
        StreamResult result = new StreamResult(fos);
        handler.setResult(result);
        //开始
        handler.startDocument();
        AttributesImpl atts = new AttributesImpl();
        handler.startElement("", "", "weapons", atts);
        for (WeaponXml weaponXml : weaponXmls) {
            atts.clear();
            atts.addAttribute("", "", "material", "", weaponXml.getMaterial());
            atts.addAttribute("", "", "type", "", weaponXml.getType());
            handler.startElement("", "", "weapon", atts);
            atts.clear();
            handler.startElement("", "", "name", atts);
            handler.characters(weaponXml.getName().toCharArray(), 0, weaponXml.getName().length());
            handler.endElement("", "", "name");
            atts.clear();
            handler.startElement("", "", "atk", atts);
            String atk = String.valueOf(weaponXml.getAtk());
            handler.characters(atk.toCharArray(), 0, atk.length());
            handler.endElement("", "", "atk");
            atts.clear();
            handler.startElement("", "", "user", atts);
            handler.characters(weaponXml.getUser().toCharArray(), 0, weaponXml.getUser().length());
            handler.endElement("", "", "user");
            handler.endElement("", "", "weapon");
        }
        handler.endElement("", "", "weapons");
        //关闭document
        handler.endDocument();
    } catch (Exception e) {
        e.printStackTrace();
    }finally {
        if (fos != null) {
            try {
                fos.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}