Android Asynchronous Http Client-Android異步網絡請求客戶端接口

1.簡介
Android中網絡請求一般使用Apache HTTP Client或者採用HttpURLConnect，但是直接使用這兩個類庫需要寫大量的代碼才能完成網絡post和get請求，而使用android-async-http這個庫可以大大的簡化操作，它是基於Apache’s HttpClient ，所有的請求都是獨立在UI主線程之外，通過回調方法處理請求結果，採用android  Handler message 機制傳遞信息。

2.特性
(1)採用異步http請求，並通過匿名內部類處理回調結果
(2)http請求獨立在UI主線程之外
(3)採用線程池來處理併發請求
(4)採用RequestParams類創建GET/POST參數
(5)不需要第三方包即可支持Multipart file文件上傳
(6)大小隻有25kb
(7)自動爲各種移動電話處理連接斷開時請求重連
(8)超快的自動gzip響應解碼支持
(9)使用BinaryHttpResponseHandler類下載二進制文件(如圖片)
(10) 使用JsonHttpResponseHandler類可以自動將響應結果解析爲json格式
(11)持久化cookie存儲，可以將cookie保存到你的應用程序的SharedPreferences中

3.使用方法
(1)到官網http://loopj.com/android-async-http/下載最新的android-async-http-1.4.4.jar，然後將此jar包添加進Android應用程序 libs文件夾
(2)通過import com.loopj.android.http.*;引入相關類
(3)創建異步請求

AsyncHttpClient client = new AsyncHttpClient();
client.get("http://www.google.com", new AsyncHttpResponseHandler() {
    @Override
    public void onSuccess(String response) {
        System.out.println(response);
    }
});

4.建議使用靜態的Http Client對象
在下面這個例子，我們創建了靜態的http client對象，使其很容易連接到Twitter的API

import com.loopj.android.http.*;

public class TwitterRestClient {
  private static final String BASE_URL = "http://api.twitter.com/1/";

  private static AsyncHttpClient client = new AsyncHttpClient();

  public static void get(String url, RequestParams params, AsyncHttpResponseHandler responseHandler) {
      client.get(getAbsoluteUrl(url), params, responseHandler);
  }

  public static void post(String url, RequestParams params, AsyncHttpResponseHandler responseHandler) {
      client.post(getAbsoluteUrl(url), params, responseHandler);
  }

  private static String getAbsoluteUrl(String relativeUrl) {
      return BASE_URL + relativeUrl;
  }
}

然後我們可以很容易的在代碼中操作Twitter的API

import org.json.*;
import com.loopj.android.http.*;

class TwitterRestClientUsage {
    public void getPublicTimeline() throws JSONException {
        TwitterRestClient.get("statuses/public_timeline.json", null, new JsonHttpResponseHandler() {
            @Override
            public void onSuccess(JSONArray timeline) {
                // Pull out the first event on the public timeline
                JSONObject firstEvent = timeline.get(0);
                String tweetText = firstEvent.getString("text");

                // Do something with the response
                System.out.println(tweetText);
            }
        });
    }
}

5. AsyncHttpClient, RequestParams ,AsyncHttpResponseHandler三個類使用方法
(1)AsyncHttpClient
public class AsyncHttpClient extends java.lang.Object
 該類通常用在android應用程序中創建異步GET, POST, PUT和DELETE HTTP請求，請求參數通過RequestParams實例創建，響應通過重寫匿名內部類 ResponseHandlerInterface的方法處理。
例子：

AsyncHttpClient client = new AsyncHttpClient();
 client.get("http://www.google.com", new ResponseHandlerInterface() {
     @Override
     public void onSuccess(String response) {
         System.out.println(response);
     }
 });

(2)RequestParams
public class RequestParams extends java.lang.Object 
用於創建AsyncHttpClient實例中的請求參數(包括字符串或者文件)的集合
例子：

RequestParams params = new RequestParams();
 params.put("username", "james");
 params.put("password", "123456");
 params.put("email", "[email protected]");
 params.put("profile_picture", new File("pic.jpg")); // Upload a File
 params.put("profile_picture2", someInputStream); // Upload an InputStream
 params.put("profile_picture3", new ByteArrayInputStream(someBytes)); // Upload some bytes

 Map<String, String> map = new HashMap<String, String>();
 map.put("first_name", "James");
 map.put("last_name", "Smith");
 params.put("user", map); // url params: "user[first_name]=James&user[last_name]=Smith"

 Set<String> set = new HashSet<String>(); // unordered collection
 set.add("music");
 set.add("art");
 params.put("like", set); // url params: "like=music&like=art"

 List<String> list = new ArrayList<String>(); // Ordered collection
 list.add("Java");
 list.add("C");
 params.put("languages", list); // url params: "languages[]=Java&languages[]=C"

 String[] colors = { "blue", "yellow" }; // Ordered collection
 params.put("colors", colors); // url params: "colors[]=blue&colors[]=yellow"

 List<Map<String, String>> listOfMaps = new ArrayList<Map<String, String>>();
 Map<String, String> user1 = new HashMap<String, String>();
 user1.put("age", "30");
 user1.put("gender", "male");
 Map<String, String> user2 = new HashMap<String, String>();
 user2.put("age", "25");
 user2.put("gender", "female");
 listOfMaps.add(user1);
 listOfMaps.add(user2);
 params.put("users", listOfMaps); // url params: "users[][age]=30&users[][gender]=male&users[][age]=25&users[][gender]=female"

 AsyncHttpClient client = new AsyncHttpClient();
 client.post("http://myendpoint.com", params, responseHandler);

(3)public class AsyncHttpResponseHandler extends java.lang.Object implements ResponseHandlerInterface
用於攔截和處理由AsyncHttpClient創建的請求。在匿名類AsyncHttpResponseHandler中的重寫 onSuccess(int, org.apache.http.Header[], byte[])方法用於處理響應成功的請求。此外，你也可以重寫 onFailure(int, org.apache.http.Header[], byte[], Throwable), onStart(), onFinish(), onRetry() 和onProgress(int, int)方法
例子：

AsyncHttpClient client = new AsyncHttpClient();
 client.get("http://www.google.com", new AsyncHttpResponseHandler() {
     @Override
     public void onStart() {
         // Initiated the request
     }

     @Override
     public void onSuccess(int statusCode, Header[] headers, byte[] responseBody) {
         // Successfully got a response
     }

     @Override
     public void onFailure(int statusCode, Header[] headers, byte[] responseBody, Throwable error)
 {
         // Response failed :(
     }

     @Override
     public void onRetry() {
         // Request was retried
     }

     @Override
     public void onProgress(int bytesWritten, int totalSize) {
         // Progress notification
     }

     @Override
     public void onFinish() {
         // Completed the request (either success or failure)
     }
 });

6.利用PersistentCookieStore持久化存儲cookie
PersistentCookieStore類用於實現Apache HttpClient的CookieStore接口，可以自動的將cookie保存到Android設備的SharedPreferences中，如果你打算使用cookie來管理驗證會話，這個非常有用，因爲用戶可以保持登錄狀態，不管關閉還是重新打開你的app
(1)首先創建 AsyncHttpClient實例對象

AsyncHttpClient myClient = new AsyncHttpClient();

(2)將客戶端的cookie保存到PersistentCookieStore實例對象,帶有activity或者應用程序context的構造方法

PersistentCookieStore myCookieStore = new PersistentCookieStore(this);
myClient.setCookieStore(myCookieStore);

(3)任何從服務器端獲取的cookie都會持久化存儲到myCookieStore中，添加一個cookie到存儲中，只需要構造一個新的cookie對象，並且調用addCookie方法

BasicClientCookie newCookie = new BasicClientCookie("cookiesare", "awesome");
newCookie.setVersion(1);
newCookie.setDomain("mydomain.com");
newCookie.setPath("/");
myCookieStore.addCookie(newCookie);

7.利用RequestParams上傳文件
類RequestParams支持multipart file 文件上傳
(1)在RequestParams 對象中添加InputStream用於上傳

InputStream myInputStream = blah;
RequestParams params = new RequestParams();
params.put("secret_passwords", myInputStream, "passwords.txt");

(2)添加文件對象用於上傳

File myFile = new File("/path/to/file.png");
RequestParams params = new RequestParams();
try {
    params.put("profile_picture", myFile);
} catch(FileNotFoundException e) {}

(3)添加字節數組用於上傳

byte[] myByteArray = blah;
RequestParams params = new RequestParams();
params.put("soundtrack", new ByteArrayInputStream(myByteArray), "she-wolf.mp3");

8.用BinaryHttpResponseHandler下載二進制數據

BinaryHttpResponseHandler用於獲取二進制數據如圖片和其他文件
AsyncHttpClient client = new AsyncHttpClient();
String[] allowedContentTypes = new String[] { "image/png", "image/jpeg" };
client.get("http://example.com/file.png", new BinaryHttpResponseHandler(allowedContentTypes) {
    @Override
    public void onSuccess(byte[] fileData) {
        // Do something with the file
    }
});

參考資料：http://loopj.com/android-async-http/