[移动开发]Android第一行代码——第九章使用网络技术

WebView用法：在应用程序里镶嵌浏览器

 @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        WebView webView = findViewById(R.id.web_view);
        webView.getSettings().setJavaScriptEnabled(true);
        webView.setWebViewClient(new WebViewClient());
        webView.loadUrl("http://www.baidu.com");
    }

使用HTTP协议访问网络

使用HttpURLConntection

URL：统一资源定位器(Uniform Resource Locators)

加入权限：

<uses-permission android:name="android.permission.INTERNET"/>

package com.example.networktest;

import androidx.appcompat.app.AppCompatActivity;

import android.icu.text.LocaleDisplayNames;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

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

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    TextView responseText;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button sendRequest = findViewById(R.id.send_request);
        responseText = findViewById(R.id.response_text);
        sendRequest.setOnClickListener(this);
    }

    @Override
    public void onClick(View view) {
        if(view.getId() == R.id.send_request){
            sendRequestWithHttpURLConnection();
        }
    }


    private void sendRequestWithHttpURLConnection() {
        new Thread(new Runnable() {
            @Override
            public void run() {
                HttpURLConnection connection = null;
                BufferedReader reader = null;
                try {
                    //获取到HttpURLConnection实例
                    URL url = new URL("http://www.baidu.com");
                    connection = (HttpURLConnection) url.openConnection();
                    //Http请求使用方法：GET和POST。GET表示在服务器那里获取数据，POST表示希望提交数据给服务器
                    connection.setRequestMethod("GET");
                    //设置连接超时和读取时长
                    connection.setConnectTimeout(8000);
                    connection.setReadTimeout(8000);
                    //获取到服务器返回的输入流
                    Log.d("TAG","开始");
                    InputStream in = connection.getInputStream();
                    Log.d("TAG","Get");
                    //对获取到的输入流进行读取
                    reader = new BufferedReader(new InputStreamReader(in));
                    Log.d("TAG","Read");
                    StringBuilder response = new StringBuilder();
                    String line;
                    Log.d("TAG","Start");
                    while((line = reader.readLine()) != null){
                        response.append(line);
                    }
                    Log.d("TAG",response.toString());
                    showResponse(response.toString());
                } catch (Exception e) {
                    e.printStackTrace();
                }finally {
                    {
                        if(reader != null){
                            try {
                                reader.close();
                            } catch (IOException e) {
                                e.printStackTrace();
                            }
                        }
                        if(connection != null){
                            //关闭服务器
                            connection.disconnect();
                        }
                    }
                }
            }
        }).start();
    }
    private void showResponse(final String response) {
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                //在这里进行UI操作，将结果显示在界面上
                responseText.setText(response);
            }
        });
    }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <Button
        android:id="@+id/send_request"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Send Request" />

    <ScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <TextView
            android:id="@+id/response_text"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"/>
    </ScrollView>

</LinearLayout>

使用OkHttp

添加依赖

implementation("com.squareup.okhttp3:okhttp:4.2.0")

 @Override
    public void onClick(View view) {
        if(view.getId() == R.id.send_request){
            sendRequestWithOkHttp();
        }
    }
 private void sendRequestWithOkHttp() {
        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    //创建OkHttpClient实例
                    OkHttpClient client = new OkHttpClient();
                    //创建Request对象发起一条HTTP请求
                    Request request = new Request.Builder().url("http://www.baidu.com").build();
                    Response response = client.newCall(request).execute();
                    String responseData = response.body().string();
                    showResponse(responseData);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }).start();
    }

解析xml格式数据

Pull解析

private void sendRequestWithOkHttp() {
        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    //创建OkHttpClient实例
                    OkHttpClient client = new OkHttpClient();
                    //创建Request对象发起一条HTTP请求
                    Request request = new Request.Builder().url("http://10.0.2.2/get_data.xml").build();
                    Response response = client.newCall(request).execute();
                    String responseData = response.body().string();
                    showResponse(responseData);
                    parseXMLWithPull(responseData);

                } catch (IOException e) {
                    e.printStackTrace();
                }
            }


        }).start();
    }

    private void parseXMLWithPull(String xmlData) {
        XmlPullParserFactory factory = null;
        try {
            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){
                    //开始解析某个节点
                    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;
                    }
                    //完成解析某个节点
                    case XmlPullParser.END_TAG:{
                        if("app".equals(nodeName)){
                            Log.d("TAG","id is "+id);
                            Log.d("TAG","name is "+name);
                            Log.d("TAG","version is "+version);
                        }
                        break;
                    }
                    default:
                        break;
                }
                eventType = xmlPullParser.next();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

SAX解析

ContentHanlder.java

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;

    @Override
    public void startDocument() throws SAXException {
        //super.startDocument();
        id = new StringBuilder();
        name = new StringBuilder();
        version = new StringBuilder();
    }

    @Override
    public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
        //super.startElement(uri, localName, qName, attributes);
        nodeName = localName;
    }

    @Override
    public void characters(char[] ch, int start, int length) throws SAXException {
        //super.characters(ch, start, length);
        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);
        }
    }

    @Override
    public void endElement(String uri, String localName, String qName) throws SAXException {
        //super.endElement(uri, localName, qName);
        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());
            //清空stringBuilder
            id.setLength(0);
            name.setLength(0);
            version.setLength(0);
        }
    }

    @Override
    public void endDocument() throws SAXException {
        super.endDocument();
    }
}

MainActivity.java

    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格式数据

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();
        }
    }

GSON

    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());
        }
    }