面试篇--android下网络通讯机制（三种网络通讯方式）
16lz
2021-01-24
HttpClient
HttpClient是Apache对java中的HttpURLClient接口的封装，主要引用org.apache.http.**。Google在2.3版本之前推荐使用HttpClient，因为这个封装包安全性高，bug较少。
使用方法：
import java.io.BufferedReader;import java.io.IOException;import java.io.InputStreamReader;import java.util.ArrayList;import java.util.List;import org.apache.http.HttpEntity;import org.apache.http.HttpResponse;import org.apache.http.HttpStatus;import org.apache.http.NameValuePair;import org.apache.http.client.ClientProtocolException;import org.apache.http.client.HttpClient;import org.apache.http.client.entity.UrlEncodedFormEntity;import org.apache.http.client.methods.HttpGet;import org.apache.http.client.methods.HttpPost;import org.apache.http.impl.client.DefaultHttpClient;import org.apache.http.message.BasicNameValuePair;public class HttpClientUtils { private static HttpClient httpClient; private static HttpClientUtils instance = null; public static synchronized HttpClientUtils getInstance() { if (instance == null) { instance = new HttpClientUtils(); } return instance; } private HttpClientUtils() { // 学习volley请求队列，HttpClient使用单例模式 if (httpClient == null) { httpClient = new DefaultHttpClient(); } } /** * 以get方式发送请求，访问接口 * @param uri链接地址 * @return 响应数据 */ private static String doHttpGet(String uri) { BufferedReader reader = null; StringBuffer sb = null; String result = ""; HttpGet request = new HttpGet(uri); try { // 发送请求，得到响应 HttpResponse response = httpClient.execute(request); // 请求成功，statuscode返回200 if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) { reader = new BufferedReader(new InputStreamReader(response.getEntity().getContent())); sb = new StringBuffer(); String line = ""; while ((line = reader.readLine()) != null) { sb.append(line); } } } catch (ClientProtocolException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } finally { try { if (null != reader) { reader.close(); reader = null; } } catch (IOException e) { e.printStackTrace(); } } if (null != sb) { result = sb.toString(); } return result; } /** * 以post方式发送请求，访问接口 * @param uri链接地址 * @return 响应数据 */ private static String doHttpPost(String uri) { BufferedReader reader = null; StringBuffer sb = null; String result = ""; HttpPost request = new HttpPost(uri); // 保存要传递的参数 List params = new ArrayList(); // 添加参数 params.add(new BasicNameValuePair("parameter", "以Post方式发送请求")); try { // 设置字符集 HttpEntity entity = new UrlEncodedFormEntity(params, "utf-8"); // 请求对象 request.setEntity(entity); // 发送请求 HttpResponse response = httpClient.execute(request); // 请求成功 if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) { System.out.println("post success"); reader = new BufferedReader(new InputStreamReader(response.getEntity().getContent())); sb = new StringBuffer(); String line = ""; while ((line = reader.readLine()) != null) { sb.append(line); } } } catch (ClientProtocolException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } finally { try { // 关闭流 if (null != reader) { reader.close(); reader = null; } } catch (IOException e) { e.printStackTrace(); } } if (null != sb) { result = sb.toString(); } return result; }} HttpURLConnection
HttpURLConnection在java.NET下，继承自URLConnection类，相对于HttpClient具有扩展性高、灵活性高，更轻量级的优点，所以Google在2.3版本之后推荐大家使用HttpURLConnection来操作网络请求。
使用方法：
import java.io.BufferedReader;import java.io.IOException;import java.io.InputStreamReader;import java.io.ObjectOutputStream;import java.io.OutputStream;import java.net.HttpURLConnection;import java.net.URL;import java.net.URLEncoder;public class HttpURLConnectUtils { private static HttpURLConnectUtils instance = null; public static synchronized HttpURLConnectUtils getInstance() { if (instance == null) { instance = new HttpURLConnectUtils(); } return instance; } private HttpURLConnectUtils() { } // post public String dohttppost(String mUrl) throws IOException { URL url = new URL(mUrl); HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();//初始化创建HttpURLConnection实例 httpURLConnection.setConnectTimeout(5000);//推荐设置网络延时 httpURLConnection.setDoOutput(true); httpURLConnection.setDoInput(true); httpURLConnection.setUseCaches(false); httpURLConnection.setRequestProperty("Content-type", "application/x-java-serialized-object"); httpURLConnection.setRequestMethod("POST"); //设置参数 OutputStream outputStream = httpURLConnection.getOutputStream(); ObjectOutputStream objectOutputStream = new ObjectOutputStream(outputStream); String params = new String();//这里简单设置参数 params = "name=" + URLEncoder.encode("高冉", "GBK"); objectOutputStream.writeBytes(params); objectOutputStream.flush(); objectOutputStream.close(); //接收返回值 //String msg = httpURLConnection.getResponseMessage();// 接收简单string InputStreamReader inputStreamReader = new InputStreamReader(httpURLConnection.getInputStream()); BufferedReader bufferedReader = new BufferedReader(inputStreamReader); StringBuilder builder = new StringBuilder(); for (String s = bufferedReader.readLine(); s != null; s = bufferedReader.readLine()) { builder.append(s); } return builder.toString(); } // get public String dohttpget(String mUrl) throws IOException { URL url = new URL(mUrl); HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection(); httpURLConnection.setConnectTimeout(5000);//推荐设置网络延时 httpURLConnection.setRequestMethod("GET"); httpURLConnection.connect(); // String msg = httpURLConnection.getResponseMessage(); InputStreamReader inputStreamReader = new InputStreamReader(httpURLConnection.getInputStream()); BufferedReader bufferedReader = new BufferedReader(inputStreamReader); StringBuilder builder = new StringBuilder(); for (String s = bufferedReader.readLine(); s != null; s = bufferedReader.readLine()) { builder.append(s); } return builder.toString(); }}还需要注意一些细节：
1、post与get区别在于post将参数置于请求数据中，get则跟在url链接后面。
2、大文件下载操作要置于sd卡中，不要放在手机内存中操作，而且需要边读边写，不要使用Buffered做缓存。
三、我们看一个简单的socket编程，实现服务器回发客户端信息。
下面用个例子来说明：
A、客户端：
新建Android项目工程：SocketForAndroid（这个随意起名字了吧，我是以这个建立的！）
下面是main_activity.xml的代码：
?| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 | <?xml version= "1.0" encoding= "utf-8" ?> |
MainActivity.java的代码入下：
?| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 | package com.yaowen.socketforandroid; import android.os.Bundle; import android.support.v7.app.AppCompatActivity; import android.view.View; import android.widget.Button; import android.widget.EditText; import java.io.BufferedReader; import java.io.BufferedWriter; import java.io.IOException; import java.io.InputStreamReader; import java.io.OutputStreamWriter; import java.io.PrintWriter; import java.net.Socket; public class MainActivity extends AppCompatActivity { private EditText message; private Button send; @Override protected void onCreate(Bundle savedInstanceState) { super .onCreate(savedInstanceState); setContentView(R.layout.activity_main); //初始化两个UI控件 message = (EditText) findViewById(R.id.message); send = (Button) findViewById(R.id.send); //设置发送按钮的点击事件响应 send.setOnClickListener( new View.OnClickListener() { @Override public void onClick(View v) { Socket socket = null ; //获取message输入框里的输入的内容 String msg = message.getText().toString() + "\r\n" ; try { //这里必须是192.168.3.200，不可以是localhost或者127.0.0.1 socket = new Socket( "192.168.3.200" , 18888 ); PrintWriter out = new PrintWriter( new BufferedWriter( new OutputStreamWriter( socket.getOutputStream() ) ), true ); //发送消息 out.println(msg); //接收数据 BufferedReader in = new BufferedReader( new InputStreamReader( socket.getInputStream() ) ); //读取接收的数据 String msg_in = in.readLine(); if ( null != msg_in) { message.setText(msg_in); System.out.println(msg_in); } else { message.setText( "接收的数据有误!" ); } //关闭各种流 out.close(); in.close(); } catch (IOException e) { e.printStackTrace(); } finally { try { if ( null != socket) { //socket不为空时，最后记得要把socket关闭 socket.close(); } } catch (IOException e) { e.printStackTrace(); } } } }); } } |
最后别忘记添加访问网络权限：
B、服务端：
?| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 | package service; import java.io.BufferedReader; import java.io.BufferedWriter; import java.io.IOException; import java.io.InputStreamReader; import java.io.OutputStreamWriter; import java.io.PrintWriter; import java.net.ServerSocket; import java.net.Socket; public class ServerAndroid implements Runnable { @Override public void run() { Socket socket = null ; try { ServerSocket server = new ServerSocket( 18888 ); // 循环监听客户端链接请求 while ( true ) { System.out.println( "start..." ); // 接收请求 socket = server.accept(); System.out.println( "accept..." ); // 接收客户端消息 BufferedReader in = new BufferedReader( new InputStreamReader(socket.getInputStream())); String message = in.readLine(); System.out.println(message); // 发送消息，向客户端 PrintWriter out = new PrintWriter( new BufferedWriter( new OutputStreamWriter(socket.getOutputStream())), true ); out.println( "Server:" + message); // 关闭流 in.close(); out.close(); } } catch (IOException e) { e.printStackTrace(); } finally { if ( null != socket) { try { socket.close(); } catch (IOException e) { e.printStackTrace(); } } } } // 启动服务器 public static void main(String[] args) { Thread server = new Thread( new ServerAndroid()); server.start(); } } |
C、启动服务器，控制台会打印出“start...”字符串！
D、运行Android项目文件，如下图：
在输入框里输入如下字符串，点发送按钮：
服务器收到客户端发来的消息并打印到控制台：
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