1.簡介
Android中網絡請求一般使用Apache HTTP Client或者采用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,它是基于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,采用android Handler message 機制傳遞資訊。
2.特性
(1)采用異步http請求,并通過匿名内部類處理回調結果
(2)http請求獨立在UI主線程之外
(3)采用線程池來處理并發請求
(4)采用RequestParams類建立GET/POST參數
(5)不需要第三方包即可支援Multipart file檔案上傳
(6)大小隻有25kb
(7)自動為各種行動電話處理連接配接斷開時請求重連
(8)超快的自動gzip響應解碼支援
(9)使用BinaryHttpResponseHandler類下載下傳二進制檔案(如圖檔)
(10) 使用JsonHttpResponseHandler類可以自動将響應結果解析為json格式
(11)持久化cookie存儲,可以将cookie儲存到你的應用程式的SharedPreferences中
3.使用方法
(1)到官網http://loopj.com/android-async-http/下載下傳最新的android-async-http-1.4.4.jar,然後将此jar包添加進Android應用程式 libs檔案夾
(2)通過import com.loopj.android.http.*;引入相關類
(3)建立異步請求
AsyncHttpClient client = new AsyncHttpClient();
client.get("http://www.google.com", new AsyncHttpResponseHandler() {
@Override
public void onSuccess(String response) {
System.out.println(response);
}
});
4.建議使用靜态的Http Client對象
在下面這個例子,我們建立了靜态的http client對象,使其很容易連接配接到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應用程式中建立異步GET, POST, PUT和DELETE HTTP請求,請求參數通過RequestParams執行個體建立,響應通過重寫匿名内部類 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
用于建立AsyncHttpClient執行個體中的請求參數(包括字元串或者檔案)的集合
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
用于攔截和處理由AsyncHttpClient建立的請求。在匿名類AsyncHttpResponseHandler中的重寫 onSuccess(int, org.apache.http.Header[], byte[])方法用于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
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類用于實作Apache HttpClient的CookieStore接口,可以自動的将cookie儲存到Android裝置的SharedPreferences中,如果你打算使用cookie來管理驗證會話,這個非常有用,因為使用者可以保持登入狀态,不管關閉還是重新打開你的app
(1)首先建立 AsyncHttpClient執行個體對象
AsyncHttpClient myClient = new AsyncHttpClient();
(2)将用戶端的cookie儲存到PersistentCookieStore執行個體對象,帶有activity或者應用程式context的構造方法
PersistentCookieStore myCookieStore = new PersistentCookieStore(this);
myClient.setCookieStore(myCookieStore);
(3)任何從伺服器端擷取的cookie都會持久化存儲到myCookieStore中,添加一個cookie到存儲中,隻需要構造一個新的cookie對象,并且調用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上傳檔案
類RequestParams支援multipart file 檔案上傳
(1)在RequestParams 對象中添加InputStream用于上傳
InputStream myInputStream = blah;
RequestParams params = new RequestParams();
params.put("secret_passwords", myInputStream, "passwords.txt");
(2)添加檔案對象用于上傳
File myFile = new File("/path/to/file.png");
RequestParams params = new RequestParams();
try {
params.put("profile_picture", myFile);
} catch(FileNotFoundException e) {}
byte[] myByteArray = blah;
RequestParams params = new RequestParams();
params.put("soundtrack", new ByteArrayInputStream(myByteArray), "she-wolf.mp3");
BinaryHttpResponseHandler用于擷取二進制資料如圖檔和其他檔案
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
}
});