android-async-http，是一个android异步网络数据请求框架，网络处理均基于Android的非UI线程，通过回调方法处理请求结果。本篇简单介绍一下它的用法，分别实现上传和下载文件的功能。

一.android-async-http简介

开源项目android-async-http地址：
https://github.com/loopj/android-async-http
android-async-http核心组件：
a). AsyncHttpResponseHandler ——这是一个请求返回处理，成功，失败，开始，完成，等自定义的消息的类；
b). BinaryHttpResponseHandler extends AsyncHttpResponseHandler ——继承AsyncHttpResponseHandler的子类，这是一个字节流返回处理的类，该类用于处理图片等类；
c). JsonHttpResponseHandler extends AsyncHttpResponseHandler ——继承AsyncHttpResponseHandler的子类，这是一个json请求返回处理服务器与客户端用json交流时使用的类；
d). AsyncHttpRequest implements Runnable ——基于线程的子类，用于异步请求类，通过AsyncHttpResponseHandler回调。
e). PersistentCookieStore implements CookieStore ——这是一个基于CookieStore的子类，使用HttpClient处理数据，并且使用cookie持久性存储接口。

f). RequestParams ——封装了参数处理例如：
```
RequestParams params = new RequestParams();params.put("uid", "00001");params.put("password", "111111");
```
核心操作类：
a). RetryHandler implements HttpRequestRetryHandler——这是一个多个线程同步处理的类；
b). SerializableCookie implements Serializable——这是操作cookie 放入/取出数据的类；
c). SimpleMultipartEntity implements HttpEntity——用于处理多个请求实体封装；
d). SyncHttpClient extends AsyncHttpClient——同步客户端请求的类；
e). AsyncHttpClient——异步客户端请求的类。

二.android-async-http实践

HttpClientUtil封装类的实现：
这个class对AsyncHttpClient进行了封装。

public class HttpClientUtil {    // 实例话对象    private static AsyncHttpClient client = new AsyncHttpClient();    static {        client.setTimeout(11000); // 设置链接超时，如果不设置，默认为10s    }    public static AsyncHttpClient getClient() {        return client;    }    // 用一个完整url获取一个string对象    public static void get(String urlString, AsyncHttpResponseHandler res) {        client.get(urlString, res);    }    // url里面带参数    public static void get(String urlString, RequestParams params,            AsyncHttpResponseHandler res) {        client.get(urlString, params, res);    }    // 不带参数，获取json对象或者数组    public static void get(String urlString, JsonHttpResponseHandler res) {        client.get(urlString, res);    }    // 带参数，获取json对象或者数组    public static void get(String urlString, RequestParams params,            JsonHttpResponseHandler res) {        client.get(urlString, params, res);    }    // 下载数据使用，会返回byte数据    public static void get(String uString, BinaryHttpResponseHandler bHandler) {        client.get(uString, bHandler);    }    //多个url？    public static void get(String urlString, RequestParams params,            BinaryHttpResponseHandler bHandler) {        client.get(urlString, params, bHandler);    }    //post    public static void post(String urlString, RequestParams params,            ResponseHandlerInterface bHandler) {        client.post(urlString, params, bHandler);    }

2. MyImageDownLoader的实现：

提供了下载图片的函数

  public class MyImageDownLoader {    private static final String TAG = "MyImageDownLoader";    Context mContext;    public interface DownLoaderListener {        public void onResult(int res, String s);    }    public MyImageDownLoader() {    }  //download image    public void downloadImage(String uri, String savePath, DownLoaderListener downLoaderListener){          // 指定文件类型          String[] allowedContentTypes = new String[] { "image/png", "image/jpeg" };          HttpClientUtil.get(uri, new ImageResponseHandler(allowedContentTypes,savePath, downLoaderListener));        }        public class ImageResponseHandler extends BinaryHttpResponseHandler{            private String[] allowedContentTypes;            private String savePathString;          DownLoaderListener mDownLoaderListener;          public ImageResponseHandler(String[] allowedContentTypes, String path, DownLoaderListener downLoaderListener){                super();                this.allowedContentTypes = allowedContentTypes;                savePathString = path;              mDownLoaderListener = downLoaderListener;          }          @Override        public void onSuccess(int statusCode, Header[] headers,                byte[] binaryData) {            Log.i(TAG, " statusCode=========" + statusCode);            Log.i(TAG, " statusCode=========" + headers);            Log.i(TAG, " statusCode====binaryData len=====" + binaryData.length);            if (statusCode == 200 && binaryData!=null && binaryData.length > 0) {                boolean b = saveImage(binaryData,savePathString);                 if (b) {                    mDownLoaderListener.onResult(0, savePathString);                }                else {                    //fail                    mDownLoaderListener.onResult(-1, savePathString);                }            }        }        @Override        public void onFailure(int statusCode, Header[] headers,                byte[] binaryData, Throwable error) {            Log.i(TAG, "download failed");        }          private boolean saveImage(byte[] binaryData, String savePath) {            Bitmap bmp = BitmapFactory.decodeByteArray(binaryData, 0,                      binaryData.length);              Log.i(TAG,"saveImage==========" +  savePath);            File file = new File(savePath);              // 压缩格式              CompressFormat format = Bitmap.CompressFormat.JPEG;              // 压缩比例              int quality = 100;              try {                  if (file.createNewFile()){                    OutputStream stream = new FileOutputStream(file);                      // 压缩输出                      bmp.compress(format, quality, stream);                      stream.close();                      return true;                }            } catch (IOException e) {                 Log.i(TAG,"saveImage====003======" +  savePath);                e.printStackTrace();              }              Log.i(TAG,"saveImage====004======" +  savePath);            return false;        }      }}

3. HttpAsyncUploader的实现：

/** * 异步上传单个文件 */public class HttpAsyncUploader {    private static final String TAG = "HttpAsyncUploader";    Context mContext;    public HttpAsyncUploader() {    }    public void uploadFile(String uri, String path) {        File file = new File(path);        RequestParams params = new RequestParams();        try {            params.put("image", file, "application/octet-stream");            AsyncHttpClient client = new AsyncHttpClient();            HttpClientUtil.post(path, params, new AsyncHttpResponseHandler() {                @Override                public void onSuccess(int statusCode, Header[] headers,                        byte[] responseBody) {                    Log.i(TAG, " statusCode=========" + statusCode);                    Log.i(TAG, " statusCode=========" + headers);                    Log.i(TAG, " statusCode====binaryData len====="+ responseBody.length);                }                @Override                public void onFailure(int statusCode, Header[] headers,                        byte[] responseBody, Throwable error) {                    Log.i(TAG, " statusCode=========" + statusCode);                    Log.i(TAG, " statusCode=========" + headers);                    Log.i(TAG, " statusCode====binaryData len====="+ responseBody.length);                    Log.i(TAG," statusCode====error====="+ error.getLocalizedMessage());                }            });        } catch (FileNotFoundException e) {        }    }}

4. 调用方法：仅以MyImageDownLoader 来举例说明。

1）MyImageDownLoader 测试函数（在activity中实现）：

private static String URL_PHOTO = "http://img001.us.expono.com/100001/100001-1bc30-2d736f_m.jpg";private void downloadTest() {    String url =URL_PHOTO；    String fileName = "" + System.currentTimeMillis() + ".jpg";    String savePath = mContext.getCacheDir() + File.separator + fileName;    MyImageDownLoader mMyImageDownLoader = new MyImageDownLoader();        // 开始异步下载    mMyImageDownLoader.downloadImage(            url,            savePath,            new DownLoaderListener() {                @Override                public void onResult(int res, String s) {                    Log.i(TAG,"onResult====res===" + res);                    Log.i(TAG, "onResult====s===" + s);                    if (res == 0) {                        // 下载成功                        Toast.makeText(mContext, "download success!", Toast.LENGTH_LONG).show();                        } else {                            // 下载photo失败                            Toast.makeText(mContext, "download fail!", Toast.LENGTH_LONG).show();                        }                    }                });    }

5 项目demo地址：

https://github.com/ranke/HttpAsyncTest/tree/master/code/src/com/util/http

开源的力量是无穷的！

网络数据请求实践一：android-async-http实现下载和上传