转载出处:http://blog.csdn.NET/lmj623565791/article/details/24589837
Volley的所有的请求的超类型是Resuest,类结构如下图,所有我们常用的请求都是这个类的子类,那么我们自定义Request肯定也是基于这个类的。
一些简单的用法实例:
- RequestQueue newRequestQueue = Volley.newRequestQueue(MainActivity.this);
- StringRequest stringRequest = new StringRequest("http://www.baidu.com", new Response.Listener<String>()
- {
- @Override
- public void onResponse(String response)
- {
- Log.e("TAG", response);
- }
- }, new Response.ErrorListener()
- {
- @Override
- public void onErrorResponse(VolleyError error)
- {
- Log.e("TAG", error.getMessage(), error);
- }
- });
- JsonObjectRequest jsonObjectRequest = new JsonObjectRequest("http://m.weather.com.cn/data/101010100.html",
- null, new Response.Listener<JSONObject>()
- {
- @Override
- public void onResponse(JSONObject response)
- {
- Log.e("TAG", response.toString());
- }
- }, new Response.ErrorListener()
- {
- @Override
- public void onErrorResponse(VolleyError error)
- {
- Log.e("TAG", error.getMessage(), error);
- }
- });
- ImageRequest imageRequest = new ImageRequest("http://imgt6.bdstatic.com/it/u=2,887966933&fm=19&gp=0.jpg",
- new Response.Listener<Bitmap>()
- {
- @Override
- public void onResponse(Bitmap response)
- {
- mImageView.setImageBitmap(response);
- }
- }, 0, 0, Config.RGB_565, null);
- newRequestQueue.add(stringRequest);
- newRequestQueue.add(imageRequest);
- newRequestQueue.add(jsonObjectRequest);
基本都是new一个请求,加入请求队列就行了。
好了,下面进入正题,如何自定义自己的Request,其实很简单,咱们打开StringRequest的源码:
- public StringRequest(int method, String url, Listener<String> listener,
- ErrorListener errorListener) {
- super(method, url, errorListener);
- mListener = listener;
- }
构造方法中指明访问的url,method,和回调的接口,毕竟我们要处理数据么。
- @Override
- protected Response<String> parseNetworkResponse(NetworkResponse response) {
- String parsed;
- try {
- parsed = new String(response.data, HttpHeaderParser.parseCharset(response.headers));
- } catch (UnsupportedEncodingException e) {
- parsed = new String(response.data);
- }
- return Response.success(parsed, HttpHeaderParser.parseCacheHeaders(response));
- }
最终给我们返回的数据就是parsed,比如我们返回的是json字符串,我们就可以在这添几行代码,把字符串转换成对象返回。(很重要的是,返回类型是咱们声明Request的时候定的,是个泛型)。
下面直接上例子:
例子是,通过客户端访问服务器,服务器对客户端进行身份校验后,返回JSON字符串,客户端直接拿到对象。
1、对象:
- package com.zhy.velloydemo;
- public class User
- {
- private String name;
- private int age;
- public String getName()
- {
- return name;
- }
- public void setName(String name)
- {
- this.name = name;
- }
- public int getAge()
- {
- return age;
- }
- public void setAge(int age)
- {
- this.age = age;
- }
- @Override
- public String toString()
- {
- return "User [name=" + name + ", age=" + age + "]";
- }
- }
2、自定义的Request
- package com.zhy.velloydemo;
- import java.io.UnsupportedEncodingException;
- import java.util.HashMap;
- import java.util.Map;
- import com.android.volley.AuthFailureError;
- import com.android.volley.NetworkResponse;
- import com.android.volley.ParseError;
- import com.android.volley.Request;
- import com.android.volley.Response;
- import com.android.volley.Response.ErrorListener;
- import com.android.volley.Response.Listener;
- import com.android.volley.toolbox.HttpHeaderParser;
- import com.google.gson.Gson;
- import com.google.gson.JsonSyntaxException;
- public class JsonRequestWithAuth<T> extends Request<T>
- {
- private final Gson gson = new Gson();
- private final Class<T> clazz;
- private final Listener<T> listener;
- private static Map<String, String> mHeader = new HashMap<String, String>();
- /**
- * 设置访问自己服务器时必须传递的参数,密钥等
- */
- static
- {
- mHeader.put("APP-Key", "LBS-AAA");
- mHeader.put("APP-Secret", "ad12msa234das232in");
- }
- /**
- * @param url
- * @param clazz
- * 我们最终的转化类型
- * @param headers
- * 请求附带的头信息
- * @param listener
- * @param appendHeader
- * 附加头数据
- * @param errorListener
- */
- public JsonRequestWithAuth(String url, Class<T> clazz, Listener<T> listener, Map<String, String> appendHeader,
- ErrorListener errorListener)
- {
- super(Method.GET, url, errorListener);
- this.clazz = clazz;
- this.listener = listener;
- mHeader.putAll(appendHeader);
- }
- @Override
- public Map<String, String> getHeaders() throws AuthFailureError
- {
- // 默认返回 return Collections.emptyMap();
- return mHeader;
- }
- @Override
- protected void deliverResponse(T response)
- {
- listener.onResponse(response);
- }
- @Override
- protected Response<T> parseNetworkResponse(NetworkResponse response)
- {
- try
- {
- /**
- * 得到返回的数据
- */
- String jsonStr = new String(response.data, HttpHeaderParser.parseCharset(response.headers));
- /**
- * 转化成对象
- */
- return Response.success(gson.fromJson(jsonStr, clazz), HttpHeaderParser.parseCacheHeaders(response));
- } catch (UnsupportedEncodingException e)
- {
- return Response.error(new ParseError(e));
- } catch (JsonSyntaxException e)
- {
- return Response.error(new ParseError(e));
- }
- }
- }
这里说一下,我在Header中放置了APP-key等数据,也就是说只要我们这个请求发的都会有这几个值,大家开发app时肯定有很多请求参数是需要每次都发往服务器校验的,可以在这里设置。
3、服务器代码:
- package com.zhy.servelt;
- import java.io.IOException;
- import java.io.PrintWriter;
- import javax.servlet.ServletException;
- import javax.servlet.ServletOutputStream;
- import javax.servlet.http.HttpServlet;
- import javax.servlet.http.HttpServletRequest;
- import javax.servlet.http.HttpServletResponse;
- public class TestServlet extends HttpServlet
- {
- public void doGet(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException
- {
- this.doPost(request, response);
- }
- public void doPost(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException
- {
- request.setCharacterEncoding("utf-8");
- String appKey = request.getHeader("APP-Key");
- String appSecret = request.getHeader("APP-Secret");
- String username = request.getHeader("username");
- String password = request.getHeader("password");
- if ("admin".equals(username) && "123".equals(password))
- {
- response.setContentType("text/plain;charset=utf-8");
- PrintWriter out = response.getWriter();
- out.print("{\"name\":\"鸿洋\",\"age\":32}");
- out.flush();
- }
- }
- }
4、测试代码:
- Map<String, String> appendHeader = new HashMap<String, String>();
- appendHeader.put("username", "admin");
- appendHeader.put("password", "123");
- String url = "http://172.27.35.1:8080/webTest/TestServlet";
- JsonRequestWithAuth<User> userRequest = new JsonRequestWithAuth<User>(url, User.class, new Listener<User>()
- {
- @Override
- public void onResponse(User response)
- {
- Log.e("TAG", response.toString());
- }
- }, appendHeader, null);
- newRequestQueue.add(userRequest);
可以看到我们使用自定义请求实现了我们上述的需求,这里还要说一下,这个例子有两个目的:
1、自定义Request其实很简单,如果不需要Header直接不用复写getHeader那个方法。
2、我们可以利用Header传递一些固定的参数,这比对安全比较高的系统,每次拼一堆xml去服务器,代码能简洁很多,当然了,注意信息安全。
最后补充一下:
HttpHeaderParser.parseCharset(response.headers)其实就是获取我们的返回流的编码,也就是我上面服务器设置的utf-8。
对于请求的Header和响应Header理解,随便打开个网站,使用浏览器的工具查看一下,每个请求都会包含这两个Header数据。