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-1.4.9.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
[java] view plaincopy
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
[java] view plaincopy
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:
[java] view plaincopy
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:
[java] view plaincopy
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);
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:
[java] view plaincopy
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
[java] view plaincopy
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
[java] view plaincopyPersistentCookieStore 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
[java] view plaincopyBasicClientCookie 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
[java] view plaincopy
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
[java] view plaincopyFile 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
[java] view plaincopybyte[] 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
[java] view plaincopy
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
}
});
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android-async-http 開源框架可以使我們輕鬆地獲取網絡數據或者向服務器發送數據,最關鍵的是,它是異步框架,在底層使用線程池處理併發請求,效率很高,使用又特別簡單。
以往我們在安卓上做項目,比如要下載很多圖片、網頁或者其他的資源,多數開發者會選擇一個線程一個下載任務這種模型,因爲安卓自帶的 AndroidHttpClient 或者 java 帶的 java.net.URL ,默認都是阻塞式操作。這種模型效率不高,對併發要求高的 APP 來講,並不適用。有的人會選擇使用 nio 自己實現,代碼複雜度又很高。
AsyncHttpClient 作爲 android-async-http 框架的一個核心應用類,使用簡單,可以處理文本、二進制等各種格式的 web 資源。下面提供一些代碼來看如何使用:
[java] view plaincopy在CODE上查看代碼片派生到我的代碼片
public class Downloader {
public static AsyncHttpClient mHttpc = new AsyncHttpClient();
public static String TAG = "Downloader";
public void downloadText(String uri){
mHttpc.get(uri, null, new AsyncHttpResponseHandler(){
@Override
public void onSuccess(String data){
Log.i(TAG, "downloaded, thread id " + Thread.currentThread().getId());
// TODO: do something on
}
@Override
public void onFailure(Throwable e, String data){
Log.i(TAG, "download failed.");
// TODO: error proceed
}
});
}
public void downloadImage(String uri, String savePath){
mHttpc.get(uri, new ImageResponseHandler(savePath));
}
public class ImageResponseHandler extends BinaryHttpResponseHandler{
private String mSavePath;
public ImageResponseHandler(String savePath){
super();
mSavePath = savePath;
}
@Override
public void onSuccess(byte[] data){
Log.i(TAG, "download image, file length " + data.length);
// TODO: save image , do something on image
}
@Override
public void onFailure(Throwable e, String data){
Log.i(TAG, "download failed");
// TODO : error proceed
}
}
};
上面的代碼演示瞭如何使用 AsyncHttpResponseHandler 和 BinaryHttpResponseHandler ,相信 AsyncHttpClient 會給大家帶來很大的便利。
AsyncHttpClient框架下載地址:http://loopj.com/android-async-http/