使用Pull解析方式，对每个节点一个个进行解析。

public class XmlParseTestActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_xml_parse_test);
    }

    private void sendRequestWithOkHttp() {
        new Thread(new Runnable() {
            @Override
            public void run() {

                try {
                    OkHttpClient client = new OkHttpClient();
                    Request request = new Request.Builder()
                            .url("192.168.1.1/ok.xml")
                            .build();
                    Response response = client.newCall(request).execute();
                    String responseString = response.body().string();
                    parseXml(responseString);
                } catch (IOException e) {
                    e.printStackTrace();
                }

            }
        }).start();
    }

    private void parseXml(String responseString) {
        try {
            XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
            XmlPullParser parser = factory.newPullParser();
            parser.setInput(new StringReader(responseString));
            int eventType = parser.getEventType();
            String id = "";
            String name = "";
            String version = "";
            String nodeName = parser.getName();
            while (eventType != XmlPullParser.END_DOCUMENT) {
                switch (eventType) {
                    case XmlPullParser.START_TAG:
                        if ("id".equals(nodeName)) {
                            id = parser.nextText();
                        } else if ("name".equals(nodeName)) {
                            name = parser.nextText();
                        } else if ("version".equals(nodeName)) {
                            version = parser.nextText();
                        }
                        break;
                    //完成一个节点的解析
                    case XmlPullParser.END_TAG:
                        if ("app".equals(nodeName)) {
                            Log.i("lyh", "id and name and version:" + id + ", " + name + ", " + version);
                        }
                        break;
                    default:
                        break;
                }
                eventType = parser.next();
            }
        } catch (XmlPullParserException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

遗留问题：
XmlPullParser适用于哪些情况？？

使用SAX解析方式 （Simple Api for Xml）

• 用法较PullParser稍微复杂一点
• 语意清晰

1. 写一个自定义的Handler类继承DefaultHandler，实现如下几个方法：

public class MySAXHandler extends DefaultHandler {

    private String eleName;
    private StringBuilder id;
    private StringBuilder name;
    private StringBuilder version;

    /**
     * called when start parsing a xml document
     * @throws SAXException
     */
    @Override
    public void startDocument() throws SAXException {
        id = new StringBuilder();
        name = new StringBuilder();
        version = new StringBuilder();
    }

    /**
     * Receive notification of the start of an element.
     *
     * <p>By default, do nothing.  Application writers may override this
     * method in a subclass to take specific actions at the start of
     * each element (such as allocating a new tree node or writing
     * output to a file).</p>
     *
     * @param uri The Namespace URI, or the empty string if the
     *        element has no Namespace URI or if Namespace
     *        processing is not being performed.
     * @param localName The local name (without prefix), or the
     *        empty string if Namespace processing is not being
     *        performed.
     * @param qName The qualified name (with prefix), or the
     *        empty string if qualified names are not available.
     * @param attributes The attributes attached to the element.  If
     *        there are no attributes, it shall be an empty
     *        Attributes object.
     * @exception org.xml.sax.SAXException Any SAX exception, possibly
     *            wrapping another exception.
     * @see org.xml.sax.ContentHandler#startElement
     */
    @Override
    public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
        eleName = localName;
    }

    /**
     * Receive notification of character data inside an element.
     *
     * <p>By default, do nothing.  Application writers may override this
     * method to take specific actions for each chunk of character data
     * (such as adding the data to a node or buffer, or printing it to
     * a file).</p>
     *
     * @param ch The characters.
     * @param start The start position in the character array.
     * @param length The number of characters to use from the
     *               character array.
     * @exception org.xml.sax.SAXException Any SAX exception, possibly
     *            wrapping another exception.
     * @see org.xml.sax.ContentHandler#characters
     */
    @Override
    public void characters(char[] ch, int start, int length) throws SAXException {
        super.characters(ch, start, length);
        if("id".equals(eleName)){
            id.append(ch, start, length);
        } else if("name".equals(eleName)){
            name.append(ch, start, length);
        } else if ("version".equals(eleName)){
            version.append(ch, start, length);
        }
    }

    @Override
    public void endElement(String uri, String localName, String qName) throws SAXException {
        super.endElement(uri, localName, qName);
        //finished parsing one element, you should clear your String Builders here
        id.setLength(0);
        name.setLength(0);
        version.setLength(0);
    }

    @Override
    public void endDocument() throws SAXException {
        super.endDocument();
        //for this occasion, we don't have to do anything
    }
}

2.将上一节parseXml方法修改为parseXmlWithSax方法

    private void parseXmlWithSAX(String responseString) {
        try {
            SAXParserFactory factory = SAXParserFactory.newInstance();
            XMLReader reader = factory.newSAXParser().getXMLReader();
            MySAXHandler saxHandler = new MySAXHandler();
            reader.setContentHandler(saxHandler);
            reader.parse(new InputSource(new StringReader(responseString)));
        } catch (Exception e){
            e.printStackTrace();
        }
    }