第一行代码--第九章-使用网络技术

这一章的内容主要有使用WebView展示网页，使用HTTP协议访问网络，解析xml数据以及解析json数据，下面是我自己的总结：

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WebView

在应用程序里展示网页

简单用法

WebView webview=(Webview)findViewById(R.id.web_view);
webview.getSettings().setJavaScriptEnabled(true);//设置支持的脚本
webview.setWebViewClient(new WebViewClient());
webview.loadUri("http://www.baidu.com");

---

使用HttpURLConnection

1. 初始化一个URL：URL url=new URL(网址)
2. 初始化一个HttpURLConnection：HttpURLConnection connection= (HttpURLConnection)url.openConnection()
3. setRequestMethod(“GET/POST”)
4. setConnectTimeout()
5. setReadTimeout()
6. InputStream in=connection.getInputStream()

---

使用OkHttp

添加依赖

compile 'com.squareup.okhttp3:okhttp:3.4.1'

GET请求

OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder()
        // 指定访问的服务器地址是电脑本机
        .url("http://10.0.2.2/get_data.json")
        .build();
Response response = client.newCall(request).execute();
String responseData = response.body().string();

POST请求

OkHttpClient client = new OkHttpClient();
RequestBody requestBody=new FormBody.Builder().add("usename","admin").add("password","123456").build();
Request request = new Request.Builder()
        // 指定访问的服务器地址是电脑本机
        .url("http://10.0.2.2/get_data.json")
        .post(requestBody)
        .build();
Response response = client.newCall(request).execute();
String responseData = response.body().string();

---

解析xml数据

Pull解析

	private void parseXMLWithPull(String xmlData) {
	   try{
			XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
            XmlPullParser xmlPullParser = factory.newPullParser();
            xmlPullParser.setInput(new StringReader(xmlData));
            int eventType = xmlPullParser.getEventType();
            String id = "";
            String name = "";
            String version = "";
            while (eventType != XmlPullParser.END_DOCUMENT) {
                String nodeName = xmlPullParser.getName();
                switch (eventType) {
                    // 开始解析某个结点
                    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;
                    }
                    // 完成解析某个结点
                    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 = xmlPullParser.next();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

SAX解析

//执行SAX前先写一个类
package com.example.networktest;

import android.util.Log;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

public class ContentHandler extends DefaultHandler {

    private String nodeName;

    private StringBuilder id;

    private StringBuilder name;

    private StringBuilder version;

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

	//在开始解析某一节点时调用
    @Override
    public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
        // 记录当前结点名
        nodeName = localName;
    }

	//在获取节点中内容时调用
    @Override
    public void characters(char[] ch, int start, int length) throws SAXException {
        // 根据当前的结点名判断将内容添加到哪一个StringBuilder对象中
        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);
        }
    }

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

	//在完成整个解析时调用
    @Override
    public void endDocument() throws SAXException {
        super.endDocument();
    }
}

//执行SAX解析的方法
private void parseXMLWithSAX(String xmlData) {
        try {
            SAXParserFactory factory = SAXParserFactory.newInstance();
            XMLReader xmlReader = factory.newSAXParser().getXMLReader();
            ContentHandler handler = new ContentHandler();
            // 将ContentHandler的实例设置到XMLReader中
            xmlReader.setContentHandler(handler);
            // 开始执行解析
            xmlReader.parse(new InputSource(new StringReader(xmlData)));
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

---

解析json数据

使用JSONObject

private void parseJSONWithJSONObject(String jsonData) {
        try {
            JSONArray jsonArray = new JSONArray(jsonData);
            for (int i = 0; i < jsonArray.length(); i++) {
                JSONObject jsonObject = jsonArray.getJSONObject(i);
                String id = jsonObject.getString("id");
                String name = jsonObject.getString("name");
                String version = jsonObject.getString("version");
                Log.d("MainActivity", "id is " + id);
                Log.d("MainActivity", "name is " + name);
                Log.d("MainActivity", "version is " + version);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

使用GSON

先创建一个App类：

package com.example.networktest;

public class App {

    private String id;

    private String name;

    private String version;

    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 getVersion() {
        return version;
    }

    public void setVersion(String version) {
        this.version = version;
    }

}

再用GSON解析数据

private void parseJSONWithGSON(String jsonData) {
        Gson gson = new Gson();
        List<App> appList = gson.fromJson(jsonData, new TypeToken<List<App>>() {}.getType());
        for (App app : appList) {
            Log.d("MainActivity", "id is " + app.getId());
            Log.d("MainActivity", "name is " + app.getName());
            Log.d("MainActivity", "version is " + app.getVersion());
        }
    }

---

封装网络请求代码

创建一个类HttpUtil，并把发送网络请求的代码写进类中相应的静态函数中，使用时直接调用即可

package com.example.networktest;

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

import okhttp3.Callback;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;

public class HttpUtil {

    public static void sendHttpRequest(final String address, final HttpCallbackListener listener) {
        new Thread(new Runnable() {
            @Override
            public void run() {
                HttpURLConnection connection = null;
                try {
                    URL url = new URL(address);
                    connection = (HttpURLConnection) url.openConnection();
                    connection.setRequestMethod("GET");
                    connection.setConnectTimeout(8000);
                    connection.setReadTimeout(8000);
                    connection.setDoInput(true);
                    connection.setDoOutput(true);
                    InputStream in = connection.getInputStream();
                    BufferedReader reader = new BufferedReader(new InputStreamReader(in));
                    StringBuilder response = new StringBuilder();
                    String line;
                    while ((line = reader.readLine()) != null) {
                        response.append(line);
                    }
                    if (listener != null) {
                        // 回调onFinish()方法
                        listener.onFinish(response.toString());
                    }
                } catch (Exception e) {
                    if (listener != null) {
                        // 回调onError()方法
                        listener.onError(e);
                    }
                } finally {
                    if (connection != null) {
                        connection.disconnect();
                    }
                }
            }
        }).start();
    }

    public static void sendOkHttpRequest(final String address, final okhttp3.Callback callback) {
        OkHttpClient client = new OkHttpClient();
        Request request = new Request.Builder()
                .url(address)
                .build();
        client.newCall(request).enqueue(callback);
    }

}

HttpCallbackListener

package com.example.networktest;

public interface HttpCallbackListener {

    void onFinish(String response);

    void onError(Exception e);

}

调用时在具体传入接口的实例即可