一. 如何使用Volley？
1. 首先定义一个RequestManager类，用来在Android程序启动时对Volley进行初始化。RequestManager为单例类，因为只有在程序启动时调用，所以不需要考虑并发问题。
1 /**
2 * Manager for the queue
3 */
4 public class RequestManager {
5
6 /**
7 * 请求队列
8 */
9 private static RequestQueue mRequestQueue;
10
11 /**
12 * 私有化构造函数
13 */
14 private RequestManager() {
15 // no instances
16 }
17
18 /**
19 * @param context 应用程序上下文
20 */
21 public static void init(Context context) {
22 mRequestQueue = Volley.newRequestQueue(context);
23 }
24
25 /**
26 * @return
27 * 请求队列
28 * @throws
29 * IllegalStatException if init has not yet been called
30 */
31 public static RequestQueue getRequestQueue() {
32 if (mRequestQueue != null) {
33 return mRequestQueue;
34 } else {
35 throw new IllegalStateException("Not initialized");
36 }
37 }
38 }
2. 为了方便对请求的Body（PUT或POST请求时）及响应体进行解析，我们可以继承Volley的Request类，自定义一个通过Gson来解析请求与响应的Request。
1 /**
2 * Wrapper for Volley requests to facilitate parsing of json responses.
3 */
4 public class MyGsonRequest<T> extends Request<T>{
5
6 /** Charset for request. */
7 private static final String PROTOCOL_CHARSET = "utf-8";
8 /** Content type for request. */
9 private static final String PROTOCOL_CONTENT_TYPE =
10 String.format("application/json; charset=%s", PROTOCOL_CHARSET);
11 /**
12 * Gson parser
13 */
14 private final Gson mGson;
15 /**
16 * Class type for the response
17 */
18 private final Class<T> mResponseClass;
19 private final Object mRequestBody;
20
21
22 /**
23 * Callback for response delivery
24 */
25 private final Listener<T> mListener;
26
27 /**
28 * @param method
29 * Request type.. Method.GET etc
30 * @param url
31 * path for the requests
32 * @param requestBody
33 * Q type instance as request body, if no request body needed set it to null
34 * @param responseClass
35 * expected class type for the response. Used by gson for serialization.
36 * @param listener
37 * handler for the response
38 * @param errorListener
39 * handler for errors
40 */
41 public MyGsonRequest(int method
42 , String url
43 , Object requestBody
44 , Class<T> responseClass
45 , Listener<T> listener
46 , ErrorListener errorListener) {
47
48 super(method, url, errorListener);
49 this.mRequestBody = requestBody;
50 this.mResponseClass = responseClass;
51 this.mListener = listener;
52 mGson = new Gson();
53
54 }
55
56 @Override
57 protected Response<T> parseNetworkResponse(NetworkResponse response) {
58 try {
59 String json = new String(response.data, HttpHeaderParser.parseCharset(response.headers));
60 return Response.success(mGson.fromJson(json, mResponseClass),
61 HttpHeaderParser.parseCacheHeaders(response));
62 } catch (UnsupportedEncodingException e) {
63 return Response.error(new ParseError(e));
64 } catch (JsonSyntaxException e) {
65 return Response.error(new ParseError(e));
66 }
67 }
68
69 @Override
70 protected void deliverResponse(T response) {
71 mListener.onResponse(response);
72 }
73
74 @Override
75 public String getBodyContentType() {
76 return PROTOCOL_CONTENT_TYPE;
77 }
78
79 @Override
80 public byte[] getBody() {
81 try {
82 return mRequestBody == null ? null : mGson.toJson(mRequestBody).getBytes(PROTOCOL_CHARSET);
83 } catch (UnsupportedEncodingException uee) {
84 VolleyLog
85 .wtf("Unsupported Encoding while trying to get the bytes of %s using %s",
86 mGson.toJson(mRequestBody), PROTOCOL_CHARSET);
87 return null;
88 }
89 }
90 }
需要重写Request的以下方法：
1）. parseNetworkResponse 通过Gson将服务器返回的Json字符串解析为你想要的对象 mGson.fromJson(json, mResponseClass)
2）. deliverResponse 调用你自定义的实现了Response.Listener接口的回调方法onResponse
3）. getBodyContentType 获取请求体的内容类型，如json类型，编码为utf-8
4）. getBody 获取请求体的字节数组表示。 同样是通过Gson将你的请求体中对象转换为Json字符串来获取字节数组 mGson.toJson(mRequestBody).getBytes(PROTOCOL_CHARSET)
3. 接下来可以针对不同的领域模型定义一些客户端类，比如对用户的一些服务器请求操作可以定义一个UserManager类，实现注册、登录等功能。
public class UserManager {
public static UserManager getInstance(){
if(mInstance == null) {
mInstance = new UserManager();
}
return mInstance;
}
public void register(Listener<String> listener, ErrorListener errorListener, User user){
Uri.Builder uriBuilder = Uri.parse(USER_BASE_URL).buildUpon();
String uri = uriBuilder.build().toString();
MyGsonRequest<String> request = new MyGsonRequest<String>(Method.POST
, uri
, user
, String.class
, listener
, errorListener);
Log.v(TAG, request.toString());
RequestManager.getRequestQueue().add(request);
}
}
上述代码实例化了一个request，将这个request加入Volley的请求队列中，由Volley来负责对请求进行调度处理。
3. 然后别忘了在程序的Application类中，对Volley进行初始化
1 public class MainApplication extends Application {
2 @Override
3 public void onCreate() {
4 super.onCreate();
5 RequestManager.init(this);
6 //其他初始化
7 }
8 ...
9 }
10
4. 最后在具体的Activity中，就可以通过如下方式对服务器发起注册请求了。
//比如点击注册按钮，在onClick方法中调用UserManager.getInstance().register(createLoginSuccessListener(),
createLoginErrorListener(), user);//请求成功返回时调用private Listener<String> createRegisterSuccessListener() { return new Listener<String>() { @Override public void onResponse(String response) { if (mProgressDialog != null) { mProgressDialog.dismiss(); } Toast.makeText( RegisterActivity.this, getString(R.string.msg_register_success), Toast.LENGTH_SHORT).show();
} };}
//请求失败时调用private Response.ErrorListener createRegisterErrorListener() { return new Response.ErrorListener() { @Override public void onErrorResponse(VolleyError error) { if (mProgressDialog != null) { mProgressDialog.dismiss(); } Toast.makeText( RegisterActivity.this, VolleyErrorUtil.getMessage(error, RegisterActivity.this), Toast.LENGTH_SHORT).show(); } };}
[Android]Volley源码分析（一）
时间： 2024-08-25 06:36:17