Android 开源框架 ( 六 ) Volley --- Google的轻量级网络通信框架

春衣少年当酒歌，起舞四顾以笑和。这篇文章主要讲述Android 开源框架 ( 六 ) Volley --- Google的轻量级网络通信框架相关的知识，希望能为你提供帮助。
一.Volley介绍2013年Google I/O大会上推出的一个新的android网络通信框架,目标是将HTTP的通信操作再进行简单化,除了简单易用之外，Volley在性能方面也进行了大幅度的调整，它的设计目标就是非常适合去进行数据量不大，但通信频繁的网络操作，而对于大数据量的网络操作，比如说下载文件等，Volley的表现就会非常糟糕。不过谷歌已经停止更新Volley了，现在OkHttp成为新一代网络通信的新宠。
二.Volley使用 1.导入jar包如果只是用于学习,可以通过gradle引用 compile \'com.mcxiaoke.volley:library:1.0.19\' 了解下.但是如果用于项目中,最好下载Google官方的jar包.

compile \'com.mcxiaoke.volley:library:1.0.19\'

2.授权

< uses-permission android:name="android.permission.INTERNET" />

3.使用JsonObjectRequest get请求方式示例

//1.创建一个请求队列RequestQueue RequestQueue queue= Volley.newRequestQueue(this); //2.创建StringRequest对象 JsonObjectRequest request=new JsonObjectRequest(url, new Response.Listener< JSONObject> () { @Override public void onResponse(JSONObject jsonObject) { //接收返回数据 Log.e("success",jsonObject.toString()); } }, new Response.ErrorListener() { @Override public void onErrorResponse(VolleyError volleyError) {} }); //3.将请求对象添加到请求队列中 queue.add(request);

同样还有一些其他请求:ClearCacheRequest,ImageRequest,JsonArrayRequest,JsonRequest,StringRequest 用法一样.

Android 开源框架 ( 六 ) Volley --- Google的轻量级网络通信框架

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1.ClearCacheRequest :A synthetic request used for clearing the cache. 用于清除缓存请求类
2.ImageRequest :A canned request for getting an image at a given URL and calling back with a decoded Bitmap. 通过Url获取对应解码位图decoded BitMap 请求类
3.JsonArrayRequest :A request for retrieving a {@link JSONArray} response body at a given URL. 通过Url返回一个{@ Link JSONArray}Json数组请求类
4.JsonObjectRequest :A request for retrieving a {@link JSONObject} response body at a given URL, allowing for an optional {@link JSONObject} to be passed in as part of the request body. 可以通过Url返回一个{@link JSONObject},也可以使用{@link JSONObject}当做请求Request的传递参数.
5.JsonRequest :A request for retrieving a T type response body at a given URL that also optionally sends along a JSON body in the request specified. 通过Url返回一个定义的泛型T ,也可以使用JSON当做请求Request的传递参数的类
6.StringRequest :A canned request for retrieving the response body at a given URL as a String. 通过Url返回一个String字符串请求类

4.使用JsonObjectRequest post请求方式示例Post请求,只需要在Request请求里,添加一个参数Request.Method.POST : new JsonObjectRequest(Request.Method.POST,url, new Response.Listener< JSONObject> () {...}); 其他部分一样.

RequestQueue queue= Volley.newRequestQueue(this); JsonObjectRequest request=new JsonObjectRequest(Request.Method.POST,url, new Response.Listener< JSONObject> () { @Override public void onResponse(JSONObject jsonObject) { //接收返回数据 Log.e("success",jsonObject.toString()); } }, new Response.ErrorListener() { @Override public void onErrorResponse(VolleyError volleyError) {} }); queue.add(request);

通过Request.Method.能看到Volley支持的一些请求方式:

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5.HurlStack 与 HttpClientStack 介绍 Volley是官方出的，volley在设计的时候是将具体的请求客户端做了下封装，也就是说可以支持HttpUrlConnection, HttpClient.当然也可以自己封装支持OkHttp.
【Android 开源框架 ( 六 ) Volley --- Google的轻量级网络通信框架】Volley.java类

if (stack == null) { if (Build.VERSION.SDK_INT > = 9) { //HttpURLConnection 请求方式 stack = new HurlStack(); } else { // Prior to Gingerbread, HttpUrlConnection was unreliable. // See: http://android-developers.blogspot.com/2011/09/androids-http-clients.html //HttpClient 请求方式 stack = new HttpClientStack(AndroidHttpClient.newInstance(userAgent)); } }

然后具体看下 HurlStack.java 里的HttpUrlConnection请求封装.

/** * An {@link HttpStack} based on {@link HttpURLConnection}. */ public class HurlStack implements HttpStack {private static final String HEADER_CONTENT_TYPE = "Content-Type"; /** * Create an {@link HttpURLConnection} for the specified {@code url}. */ protected HttpURLConnection createConnection(URL url) throws IOException { return (HttpURLConnection) url.openConnection(); }/** * Opens an {@link HttpURLConnection} with parameters. * @param url * @return an open connection * @throws IOException */ private HttpURLConnection openConnection(URL url, Request< ?> request) throws IOException { HttpURLConnection connection = createConnection(url); int timeoutMs = request.getTimeoutMs(); connection.setConnectTimeout(timeoutMs); connection.setReadTimeout(timeoutMs); connection.setUseCaches(false); connection.setDoInput(true); // use caller-provided custom SslSocketFactory, if any, for HTTPS if ("https".equals(url.getProtocol()) & & mSslSocketFactory != null) { ((HttpsURLConnection)connection).setSSLSocketFactory(mSslSocketFactory); }return connection; }@SuppressWarnings("deprecation") /* package */ static void setConnectionParametersForRequest(HttpURLConnection connection, Request< ?> request) throws IOException, AuthFailureError { switch (request.getMethod()) { case Method.DEPRECATED_GET_OR_POST: // This is the deprecated way that needs to be handled for backwards compatibility. // If the request\'s post body is null, then the assumption is that the request is // GET.Otherwise, it is assumed that the request is a POST. byte[] postBody = request.getPostBody(); if (postBody != null) { // Prepare output. There is no need to set Content-Length explicitly, // since this is handled by HttpURLConnection using the size of the prepared // output stream. connection.setDoOutput(true); connection.setRequestMethod("POST"); connection.addRequestProperty(HEADER_CONTENT_TYPE, request.getPostBodyContentType()); DataOutputStream out = new DataOutputStream(connection.getOutputStream()); out.write(postBody); out.close(); } break; case Method.GET: // Not necessary to set the request method because connection defaults to GET but // being explicit here. connection.setRequestMethod("GET"); break; case Method.DELETE: connection.setRequestMethod("DELETE"); break; case Method.POST: connection.setRequestMethod("POST"); addBodyIfExists(connection, request); break; case Method.PUT: connection.setRequestMethod("PUT"); addBodyIfExists(connection, request); break; case Method.HEAD: connection.setRequestMethod("HEAD"); break; case Method.OPTIONS: connection.setRequestMethod("OPTIONS"); break; case Method.TRACE: connection.setRequestMethod("TRACE"); break; case Method.PATCH: connection.setRequestMethod("PATCH"); addBodyIfExists(connection, request); break; default: throw new IllegalStateException("Unknown method type."); } }private static void addBodyIfExists(HttpURLConnection connection, Request< ?> request) throws IOException, AuthFailureError { byte[] body = request.getBody(); if (body != null) { connection.setDoOutput(true); connection.addRequestProperty(HEADER_CONTENT_TYPE, request.getBodyContentType()); DataOutputStream out = new DataOutputStream(connection.getOutputStream()); out.write(body); out.close(); } }}

在看看HttpClientStack.java 里的HttpClient的封装. 注意下哈,HttpClient 已经在Android 6.0 删除.

/** * An HttpStack that performs request over an {@link HttpClient}. */ public class HttpClientStack implements HttpStack { protected final HttpClient mClient; private final static String HEADER_CONTENT_TYPE = "Content-Type"; /** * Creates the appropriate subclass of HttpUriRequest for passed in request. */ @SuppressWarnings("deprecation") /* protected */ static HttpUriRequest createHttpRequest(Request< ?> request, Map< String, String> additionalHeaders) throws AuthFailureError { switch (request.getMethod()) { case Method.DEPRECATED_GET_OR_POST: { // This is the deprecated way that needs to be handled for backwards compatibility. // If the request\'s post body is null, then the assumption is that the request is // GET.Otherwise, it is assumed that the request is a POST. byte[] postBody = request.getPostBody(); if (postBody != null) { HttpPost postRequest = new HttpPost(request.getUrl()); postRequest.addHeader(HEADER_CONTENT_TYPE, request.getPostBodyContentType()); HttpEntity entity; entity = new ByteArrayEntity(postBody); postRequest.setEntity(entity); return postRequest; } else { return new HttpGet(request.getUrl()); } } case Method.GET: return new HttpGet(request.getUrl()); case Method.DELETE: return new HttpDelete(request.getUrl()); case Method.POST: { HttpPost postRequest = new HttpPost(request.getUrl()); postRequest.addHeader(HEADER_CONTENT_TYPE, request.getBodyContentType()); setEntityIfNonEmptyBody(postRequest, request); return postRequest; } case Method.PUT: { HttpPut putRequest = new HttpPut(request.getUrl()); putRequest.addHeader(HEADER_CONTENT_TYPE, request.getBodyContentType()); setEntityIfNonEmptyBody(putRequest, request); return putRequest; } case Method.HEAD: return new HttpHead(request.getUrl()); case Method.OPTIONS: return new HttpOptions(request.getUrl()); case Method.TRACE: return new HttpTrace(request.getUrl()); case Method.PATCH: { HttpPatch patchRequest = new HttpPatch(request.getUrl()); patchRequest.addHeader(HEADER_CONTENT_TYPE, request.getBodyContentType()); setEntityIfNonEmptyBody(patchRequest, request); return patchRequest; } default: throw new IllegalStateException("Unknown request method."); } }}