本节引言:
上节讲了HttpURLConnection，本节就到HttpClient了，Apache给我们提供的HttpClient(简单的Http客户端),
不过毕竟不是亲儿子，HttpClient在API 21版本后就给Google弃用了，而我们实际开发中，很多页面都不是通过
一个简单的URL就可以访问的，可能需要登陆或者相关权限才可以访问，这就涉及到了Session,Cookie等的问题了；
当然我们可以用HttpURLConnection来实现，但是有点麻烦，而用HttpClient可以简单点；HttpClient用于接收/发送
Http请求/响应，但不缓存服务器响应，不执行HTML页面潜入的JS代码，不会对页面内容进行任何解析，处理；
要改掉废话太多的习惯，SO简化博文，开始本节内容吧：
HttpClient使用流程:
基本流程:
HttpClient使用示例:
1.发送GET请求
嗯，就写个简单的发送GET请求的代码吧:
package com.example.httpclientdemo;import org.apache.http.HttpEntity;import org.apache.http.HttpResponse;import org.apache.http.client.HttpClient;import org.apache.http.client.methods.HttpGet;import org.apache.http.impl.client.DefaultHttpClient;import org.apache.http.util.EntityUtils;import android.app.Activity;import android.os.Bundle;import android.os.Handler;import android.os.Message;import android.view.View;import android.view.View.OnClickListener;import android.webkit.WebView;import android.widget.Button;public class MainActivity extends Activity implements OnClickListener { private Button btnGet; private WebView wView; public static final int SHOW_DATA = 0X123; private String detail = ""; private Handler handler = new Handler() { public void handleMessage(Message msg) { if(msg.what == SHOW_DATA) { wView.loadDataWithBaseURL("",detail, "text/html","UTF-8",""); } }; }; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); initView(); setView(); } private void initView() { btnGet = (Button) findViewById(R.id.btnGet); wView = (WebView) findViewById(R.id.wView); } private void setView() { btnGet.setOnClickListener(this); wView.getSettings().setDomStorageEnabled(true); } @Override public void onClick(View v) { if (v.getId() == R.id.btnGet) { GetByHttpClient(); } } private void GetByHttpClient() { new Thread() { public void run() { try { HttpClient httpClient = new DefaultHttpClient(); HttpGet httpGet = new HttpGet("http://www.w3cschool.cc/python/python-tutorial.html"); HttpResponse httpResponse = httpClient.execute(httpGet); if (httpResponse.getStatusLine().getStatusCode() == 200) { HttpEntity entity = httpResponse.getEntity(); detail = EntityUtils.toString(entity, "utf-8"); handler.sendEmptyMessage(SHOW_DATA); } } catch (Exception e) { e.printStackTrace(); } }; }.start(); }}另外，如果是带有参数的GET请求的话，我们可以把参数放到List集合中，在对参数进行URL编码:
然后和URL拼接
List<BasicNameValuePair> params = new LinkedList<BasicNameValuePair>(); params.add(new BasicNameValuePair("user", "猪小弟")); params.add(new BasicNameValuePair("pawd", "123"));String param = URLEncodedUtils.format(params, "UTF-8"); HttpGet httpGet = new HttpGet("http://www.baidu.com"+"?"+param);接着贴下运行截图:
2.发送POST请求
POST请求比GET稍微复杂一点，创建完HttpPost对象后，通过NameValuePair集合来存储等待提交
的参数，并将参数传递到UrlEncodedFormEntity中，最后调用setEntity(entity)完成，
HttpClient.execute(HttpPost)即可；这里就不写例子了，暂时没找到Post的网站，又不想
自己写个Servlet，So,直接贴核心代码吧~
核心代码:
private void PostByHttpClient(final String url) { new Thread() { public void run() { try{ HttpClient httpClient = new DefaultHttpClient(); HttpPost httpPost = new HttpPost(url); List<NameValuePair> params = new ArrayList<NameValuePair>(); params.add(new BasicNameValuePair("user", "猪大哥")); params.add(new BasicNameValuePair("pawd", "123")); UrlEncodedFormEntity entity = new UrlEncodedFormEntity(params,"UTF-8"); httpPost.setEntity(entity); HttpResponse httpResponse = httpClient.execute(httpPost); if (httpResponse.getStatusLine().getStatusCode() == 200) { HttpEntity entity2 = httpResponse.getEntity(); detail = EntityUtils.toString(entity2, "utf-8"); handler.sendEmptyMessage(SHOW_DATA); } }catch(Exception e){e.printStackTrace();} }; }.start(); }3.胡说八道
其实关于HttpClient的例子有很多，比如笔者曾经用它来抓学校教务系统上学生的课程表:
这就涉及到Cookie，模拟登陆的东西，说到抓数据(爬虫)，一般我们是搭配着JSoup来解析
抓到数据的，有兴趣可以自己查阅相关资料，至于笔者的毕设，代码很烂的说，后续有时间
整理在发布出来吧，这里贴下模拟登陆教务系统部分的代码，大家可以体会下HttpClient：
//获得链接,模拟登录的实现: public int getConnect(String user, String key) throws Exception { // 先发送get请求 获取cookie值和__ViewState值 HttpGet getLogin = new HttpGet(true_url); // 第一步:主要的HTML: String loginhtml = ""; HttpResponse loginResponse = new DefaultHttpClient().execute(getLogin); if (loginResponse.getStatusLine().getStatusCode() == 200) { HttpEntity entity = loginResponse.getEntity(); loginhtml = EntityUtils.toString(entity); // 获取响应的cookie值 cookie = loginResponse.getFirstHeader("Set-Cookie").getValue(); System.out.println("cookie= " + cookie); } // 第二步:模拟登录 // 发送Post请求,禁止重定向 HttpPost httpPost = new HttpPost(true_url); httpPost.getParams().setParameter(ClientPNames.HANDLE_REDIRECTS, false); // 设置Post提交的头信息的参数 httpPost.setHeader("User-Agent", "Mozilla/5.0 (Windows NT 6.3; WOW64; Trident/7.0; rv:11.0) like Gecko"); httpPost.setHeader("Referer", true_url); httpPost.setHeader("Cookie", cookie); // 设置请求数据 List<NameValuePair> params = new ArrayList<NameValuePair>(); params.add(new BasicNameValuePair("__VIEWSTATE", getViewState(loginhtml)));// __VIEWSTATE参数，如果变化可以动态抓取获取 params.add(new BasicNameValuePair("Button1", "")); params.add(new BasicNameValuePair("hidPdrs", "")); params.add(new BasicNameValuePair("hidsc", "")); params.add(new BasicNameValuePair("lbLanguage", "")); params.add(new BasicNameValuePair("RadioButtonList1", "%D1%A7%C9%FA")); params.add(new BasicNameValuePair("txtUserName", user)); params.add(new BasicNameValuePair("TextBox2", key)); params.add(new BasicNameValuePair("txtSecretCode", "")); // ( ╯□╰ )逗比正方,竟然不需要验证码 // 设置编码方式,响应请求,获取响应状态码: httpPost.setEntity(new UrlEncodedFormEntity(params, "gb2312")); HttpResponse response = new DefaultHttpClient().execute(httpPost); int Status = response.getStatusLine().getStatusCode(); if(Status == 200)return Status; System.out.println("Status= " + Status); // 重定向状态码为302 if (Status == 302 || Status == 301) { // 获取头部信息中Location的值 location = response.getFirstHeader("Location").getValue(); System.out.println(location); // 第三步:获取管理信息的主页面 // Get请求 HttpGet httpGet = new HttpGet(ip_url + location);// 带上location地址访问 httpGet.setHeader("Referer", true_url); httpGet.setHeader("Cookie", cookie); // 主页的html mainhtml = ""; HttpResponse httpResponseget = new DefaultHttpClient() .execute(httpGet); if (httpResponseget.getStatusLine().getStatusCode() == 200) { HttpEntity entity = httpResponseget.getEntity(); mainhtml = EntityUtils.toString(entity); } } return Status; }总结:
好的，本节关于HttpClient就到这里吧，内容还是比较简单的~
下节我们将使用retrofit来封装我们的HTTP请求，敬请期待~
对了，关于Android里简单的网络技术可以参考小猪之前写过的入门系列:
小猪的Android入门之路 day 8 part 3