Android HTTP请求方式:HttpClient

1.HttpClient使用流程
基本流程：

2.HttpClient使用示例
1）使用HttpClient发送GET请求
直接贴下简单的发送Get请求的代码：

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();
}

}
运行截图

另外，如果是带有参数的GET请求的话，我们可以将参数放到一个List集合中，再对参数进行URL编码， 最后和URL拼接下就好了：

List params = new LinkedList();
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);
2）使用HttpClient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 params = new ArrayList();
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.HttpClient抓数据示例(教务系统数据抓取)
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，这里贴下笔者毕设app里获取网页部分的关键 代码！大家可以体会下：

HttpClient可以通过下述代码获取与设置Cookie： HttpResponse loginResponse = new DefaultHttpClient().execute(getLogin); 获得Cookie:cookie = loginResponse.getFirstHeader(“Set-Cookie”).getValue(); 请求时带上Cookie:httpPost.setHeader(“Cookie”, cookie);

//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 params = new ArrayList();

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;

}
4.使用HttpPut发送Put请求
示例代码如下：

public static int PutActCode(String actCode, String licPlate, Context mContext) {
int resp = 0;
String cookie = (String) SPUtils.get(mContext, “session”, “”);
HttpPut httpPut = new HttpPut(PUTACKCODE_URL);
httpPut.setHeader(“Cookie”, cookie);
try {

    List params = new ArrayList();
    params.add(new BasicNameValuePair("activation_code", actCode));
    params.add(new BasicNameValuePair("license_plate", licPlate));
    httpPut.setEntity(new UrlEncodedFormEntity(params, "UTF-8"));
    HttpResponse course_response = new DefaultHttpClient().execute(httpPut);
    if (course_response.getStatusLine().getStatusCode() == 200) {
        HttpEntity entity2 = course_response.getEntity();
        JSONObject jObject = new JSONObject(EntityUtils.toString(entity2));
        resp = Integer.parseInt(jObject.getString("status_code"));
        return resp;
    }
} catch (Exception e) {
    e.printStackTrace();
}
return resp;

}