1.简介
Android中网络请求一般使用Apache HTTP Client或者采用HttpURLConnect，但是直接使用这两个类库需要写大量的代码才能完成网络post和get请求，而使用android-async-http这个库可以大大的简化操作，它是基于Apache’s HttpClient ，所有的请求都是独立在UI主线程之外，通过回调方法处理请求结果，采用android Handler message 机制传递信息。
2.特性
(1)采用异步http请求，并通过匿名内部类处理回调结果
(2)http请求独立在UI主线程之外
(3)采用线程池来处理并发请求
(4)采用RequestParams类创建GET/POST参数
(5)不需要第三方包即可支持Multipart file文件上传
(6)大小只有25kb
(7)自动为各种移动电话处理连接断开时请求重连
(8)超快的自动gzip响应解码支持
(9)使用BinaryHttpResponseHandler类下载二进制文件(如图片)
(10) 使用JsonHttpResponseHandler类可以自动将响应结果解析为json格式
(11)持久化cookie存储，可以将cookie保存到你的应用程序的SharedPreferences中
3.使用方法
(1)到官网http://loopj.com/android-async-http/下载最新的android-async-http-1.4.4.jar，然后将此jar包添加进Android应用程序 libs文件夹
(2)通过import com.loopj.android.http.*;引入相关类
(3)创建异步请求
AsyncHttpClient client = new AsyncHttpClient();
client.get("http://www.google.com", new AsyncHttpResponseHandler() {
@Override
public void onSuccess(String response) {
System.out.println(response);
}
});
4.建议使用静态的Http Client对象
在下面这个例子，我们创建了静态的http client对象，使其很容易连接到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;
}
}
然后我们可以很容易的在代码中操作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三个类使用方法
(1)AsyncHttpClient
public class AsyncHttpClient extends java.lang.Object
该类通常用在android应用程序中创建异步GET, POST, PUT和DELETE HTTP请求，请求参数通过RequestParams实例创建，响应通过重写匿名内部类 ResponseHandlerInterface的方法处理。
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
用于创建AsyncHttpClient实例中的请求参数(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", "my@email.com");
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
用于拦截和处理由AsyncHttpClient创建的请求。在匿名类AsyncHttpResponseHandler中的重写 onSuccess(int, org.apache.http.Header[], byte[])方法用于处理响应成功的请求。此外，你也可以重写 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持久化存储cookie
PersistentCookieStore类用于实现Apache HttpClient的CookieStore接口，可以自动的将cookie保存到Android设备的SharedPreferences中，如果你打算使用cookie来管理验证会话，这个非常有用，因为用户可以保持登录状态，不管关闭还是重新打开你的app
(1)首先创建 AsyncHttpClient实例对象
AsyncHttpClient myClient = new AsyncHttpClient();
(2)将客户端的cookie保存到PersistentCookieStore实例对象,带有activity或者应用程序context的构造方法
PersistentCookieStore myCookieStore = new PersistentCookieStore(this);
myClient.setCookieStore(myCookieStore);
(3)任何从服务器端获取的cookie都会持久化存储到myCookieStore中，添加一个cookie到存储中，只需要构造一个新的cookie对象，并且调用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上传文件
类RequestParams支持multipart file 文件上传
(1)在RequestParams 对象中添加InputStream用于上传
InputStream myInputStream = blah;
RequestParams params = new RequestParams();
params.put("secret_passwords", myInputStream, "passwords.txt");
(2)添加文件对象用于上传
File myFile = new File("/path/to/file.png");
RequestParams params = new RequestParams();
try {
params.put("profile_picture", myFile);
} catch(FileNotFoundException e) {}
(3)添加字节数组用于上传
byte[] myByteArray = blah;
RequestParams params = new RequestParams();
params.put("soundtrack", new ByteArrayInputStream(myByteArray), "she-wolf.mp3");
8.用BinaryHttpResponseHandler下载二进制数据
BinaryHttpResponseHandler用于获取二进制数据如图片和其他文件
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
}
});