Android使用Http访问并解析服务器XML数据

okhttp

使用前需添加okhttp开源库的依赖，添加方法可参考前面这篇文章

new Thread(() -> {        OkHttpClient client = new OkHttpClient();        Request request = new Request.Builder()                .url("http://127.0.0.1/a.xml")                .build();        try {            Response response = client.newCall(request).execute();            String responceData = response.body().string();            showResponce(responceData);        }        catch (IOException ioex) {            ioex.printStackTrace();        }    //            RequestBody requestBody = new FormBody.Builder()    //                    .add("username", "admin")    //                    .add("password", "123456")    //                    .build();    //            Request request1 = new Request.Builder()    //                    .url("http://www.baidu.com")    //                    .post(requestBody)    //                    .build();    //            try {    //                Response response = client.newCall(request1).execute();    //                String responceData = response.body().string();    //            }    //            catch (IOException ex) {    //                ex.printStackTrace();    //            }    }).start();

解析XML

假设有XML数据如下

<apps>    <app>        <id>1</id>        <name>Google Maps</name>        <version>1.0</version>    </app>    <app>        <id>2</id>        <name>Chrome</name>        <version>2.1</version>    </app></apps>

Pull

private void parseXMLWithPull(String responceData)    {        try {            XmlPullParserFactory factory = XmlPullParserFactory.newInstance().newInstance();            XmlPullParser xmlparser = factory.newPullParser();            xmlparser.setInput(new StringReader(responceData));            int eventType = xmlparser.getEventType();            String id = "";            String name = "";            String version = "";            while (eventType != XmlPullParser.END_DOCUMENT) {                String nodeName = xmlparser.getName();                switch (eventType)                {                    case XmlPullParser.START_TAG: {                        if("id".equals(nodeName)) {                            id = xmlparser.nextText();                        }                        else if("name".equals(nodeName)) {                            name = xmlparser.nextText();                        }                        else if("version".equals(nodeName)) {                            version = xmlparser.nextText();                        }                        break;                    }                    case XmlPullParser.END_TAG: {                        if("app".equals(nodeName)) {                            Log.d("MainActivity", "id is" + id);                            Log.d("MainActivity", "name is" + name);                            Log.d("MainActivity", "version is" + version);                        }                        break;                    }                    default:                        break;                }                eventType = xmlparser.next();            }        }        catch (Exception ex) {            ex.printStackTrace();        }    }

SAX

//创建一个类    public class MyXMLHandler extends DefaultHandler {        private String nodeName;        private  StringBuilder id;        private  StringBuilder name;        private StringBuilder version;        @Override        public void startDocument() throws SAXException {            id = new StringBuilder();            name = new StringBuilder();            version = new StringBuilder();        }                          //文本的起始        @Override        public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {            nodeName = localName;        }                           //每个节点的起始        @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, start, length);            }            else if("version".equals(nodeName)) {                version.append(ch, start, length);            }        }                          //每个节点文本内容的解析        @Override        public void endElement(String uri, String localName, String qName) throws SAXException {            if("app".equals(localName)) {                Log.d("Handler", "id is" + id.toString().trim());                Log.d("Handler", "name is" + name.toString().trim());                Log.d("Handler", "version is" + version.toString().trim());                id.setLength(0);                name.setLength(0);                version.setLength(0);            }        }                           //每个节点的结束        @Override        public void endDocument() throws SAXException {            super.endDocument();        }    }                              //文本的结束    //类的调用    private void parseXMLWithHandler(String responce)    {        try {            SAXParserFactory factory = SAXParserFactory.newInstance();            XMLReader xmlreader = factory.newSAXParser().getXMLReader();            MyXMLHandler handler = new MyXMLHandler();            xmlreader.setContentHandler(handler);            xmlreader.parse(new InputSource(new StringReader(responce)));        }        catch (Exception ex) {            ex.printStackTrace();        }    }

总结

其实，上面建立http连接的写法是有问题的。因为每次建立http连接都要重复以上代码，难免造成不必要的代码重复。我们想要的效果是：

String address = "...";String responce = HttpUtil.sendRequestAddress(address);

因此我们想到的是把http协议处理的相关方法，包装到一个类中,然后在该sendRequestAddress方法中new一个Thread即可。但是这样就不能把想要的结果返回。因此，我们这里应用一个类okhttp.Callback进行回调。

public class HttpUtil {        public static void sendHttpRequest(final String address, Callback callback)        {            OkHttpClient client = new OkHttpClient();            Request request = new Request.Builder()                    .url(address)                    .build();            client.newCall(request).enqueue(callback);        }    }

其中okhttp.Callback帮我们另外启动一个子线程处理服务器返回的数据，调用时，应用以下代码即可：

HttpUtil.sendHttpRequest("http://www.baidu.com",            new Callback() {                @Override                public void onFailure(Call call, IOException e) {                    ...                }                @Override                public void onResponse(Call call, Response response) throws IOException {                    String responseData = response.body().string();                    showResponce(responseData);                }            });

一个回调机制的简单例子

 public interface HttpCallbackListener {        void onFinish(String responce);        void onError(Exception e);    }

public class HttpUtil {        public static void sendHttpRequest(final String add, HttpCallbackListener listener) {            new Thread(() -> {                        //线程进行处理，处理时间不确定                ....                try {                    if(listener != null) {     listener.onFinish(responce.body().string());     //调用HttpCallbackListener中的函数                    }                }                catch(Exception e) {                    if(listener != null) {                       listener.onError(e);           //调用HttpCallbackListener中的函数                    }                }            }).start();        }    }

public class testResponce {        public static showResponce(String rsponce) {            ...        }        public static showError(Exception e) {            ...        }        public static void main(String[] argv) {            try{                HttpUtil.sendHttpRequest(add, new HttpCallbackListener() {                    @Override                    void onFinish(String responce) {                        showResponce(responce);                           //回调testResponce的函数                    }                    @Override                    void onError(Exception e) {                        showError(e);                                     ////回调testResponce的函数                    }                });            }            catch(Exception e) {                ...            }        }    }