Android基礎入門教程——7.1.4 Android HTTP請求方式:HttpClient

標籤（空格分隔）： Android基礎入門教程

本節引言：

在上一節中我們對HttpURLConnection進行了學習，本節到第二種方式：HttpClient，儘管被Google
棄用了，但是我們我們平時也可以拿HttpClient來抓下包，配合Jsoup解析網頁效果更佳！HttpClient
用於接收/傳送Http請求/響應，但不快取伺服器響應，不執行HTML頁面潛入的JS程式碼，不會對頁面內容
進行任何解析，處理！開始本節內容！

1.HttpClient使用流程

基本流程：

2.HttpClient使用示例

1）使用HttpClient傳送GET請求

直接貼下簡單的傳送Get請求的程式碼：

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();
    }

}

執行截圖：

另外，如果是帶有引數的GET請求的話，我們可以將引數放到一個List集合中，再對引數進行URL編碼，
最後和URL拼接下就好了：

List<BasicNameValuePair> params = new LinkedList<BasicNameValuePair>();  
params.add(new BasicNameValuePair("user", "豬小弟"));  
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傳送POST請求

POST請求比GET稍微複雜一點，建立完HttpPost物件後，通過NameValuePair集合來儲存等待提交
的引數，並將引數傳遞到UrlEncodedFormEntity中，最後呼叫setEntity(entity)完成，
HttpClient.execute(HttpPost)即可；這裡就不寫例子了，暫時沒找到Post的網站，又不想
自己寫個Servlet，So,直接貼核心程式碼吧~

核心程式碼:

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", "豬大哥"));
                    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抓資料示例(教務系統資料抓取)

其實關於HttpClient的例子有很多，比如筆者曾經用它來抓學校教務系統上學生的課程表:
這就涉及到Cookie，模擬登陸的東西，說到抓資料(爬蟲)，一般我們是搭配著JSoup來解析
抓到資料的，有興趣可以自己查閱相關資料，這裡貼下筆者畢設app裡獲取網頁部分的關鍵
程式碼！大家可以體會下：

HttpClient可以通過下述程式碼獲取與設定Cookie：
HttpResponse loginResponse = new DefaultHttpClient().execute(getLogin);
獲得Cookie:cookie = loginResponse.getFirstHeader(“Set-Cookie”).getValue();
請求時帶上Cookie**:httpPost.setHeader(“Cookie”, cookie);**

//獲得連結,模擬登入的實現:
    public int getConnect(String user, String key) throws Exception {
        // 先發送get請求 獲取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);
            // 獲取響應的cookie值
            cookie = loginResponse.getFirstHeader("Set-Cookie").getValue();
            System.out.println("cookie= " + cookie);
        }

        // 第二步:模擬登入
        // 傳送Post請求,禁止重定向
        HttpPost httpPost = new HttpPost(true_url);
        httpPost.getParams().setParameter(ClientPNames.HANDLE_REDIRECTS, false);

        // 設定Post提交的頭資訊的引數
        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);

        // 設定請求資料
        List<NameValuePair> params = new ArrayList<NameValuePair>();

        params.add(new BasicNameValuePair("__VIEWSTATE",
                getViewState(loginhtml)));// __VIEWSTATE引數，如果變化可以動態抓取獲取
        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,竟然不需要驗證碼

        // 設定編碼方式,響應請求,獲取響應狀態碼:
        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);

        // 重定向狀態碼為302
        if (Status == 302 || Status == 301) {
            // 獲取頭部資訊中Location的值
            location = response.getFirstHeader("Location").getValue();
            System.out.println(location);
            // 第三步:獲取管理資訊的主頁面
            // Get請求
            HttpGet httpGet = new HttpGet(ip_url + location);// 帶上location地址訪問
            httpGet.setHeader("Referer", true_url);
            httpGet.setHeader("Cookie", cookie);

            // 主頁的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傳送Put請求

示例程式碼如下：

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<NameValuePair> params = new ArrayList<NameValuePair>();
        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;
}

本節小結：

好的，本節關於Android HTTP的第二種請求方式:HttpClient就到這裡，
而基本請求也到這裡，下節開始我們將帶大家來學習XML以及Json的解析！
謝謝~