前言
在项目中一般使用使用volley方式如下，用起来给人一种很乱的感觉，于是一种盘它的想法油然而生。
public void get() {String url = "https://tcc.taobao.com/cc/json/mobile_tel_segment.htm?tel=......";StringRequest request = new StringRequest(Request.Method.GET, url, new Response.Listener<String>() { @Override public void onResponse(String s) { Toast.makeText(MainActivity.this,s,Toast.LENGTH_SHORT).show(); } }, new Response.ErrorListener() { @Override public void onErrorResponse(VolleyError volleyError) { Toast.makeText(MainActivity.this,volleyError.toString(),Toast.LENGTH_SHORT).show(); } }); request.setTag("abcGet"); MyApplication.getHttpQueues().add(request); } 首先看一下我封装后的使用例子:
private void initData() { NewsApi.getInfo(new NetCallback<News>() { @Override public void OnSuccess(final News result) { mAdapter.setData(result.getResult().getData()); } @Override public void OnError(RestfulError error) { } }); } 有没有看起来很舒服的感觉。好吧，让我开始盘它吧！
1.首先我先去写了一个基类，用来创建一个新的request并把它加入到volley内部封装的请求队列中，代码如下：
public abstract class AuthenticatedRequestBase<T> extends Request<T> { private final static String TAG = "AuthenticatedRequestBase"; private static final int TIME_OUT = 30000; private static final int MAX_RETRIES = 1; private static final float BACKOFF_MULT = 2f; protected Context mContext; protected RequestQueue mRequestQueue; /** * 创建新的请求，并把请求加入到请求队列requestQueue中 * * @param method * @param url * @param cache * @param errorListener */ @SuppressLint("LongLogTag") public AuthenticatedRequestBase(int method, String url, boolean cache, Response.ErrorListener errorListener) { super(method, url, errorListener); //this.setShouldCache(cache); this.setRetryPolicy(new DefaultRetryPolicy( TIME_OUT, MAX_RETRIES, BACKOFF_MULT)); mRequestQueue = YZ.getInstance().getRequestQueue(); if (mRequestQueue == null) { throw new IllegalArgumentException("mRequestQueue can't be null"); } mContext = YZ.getInstance().getContext(); if (mContext == null) { throw new IllegalArgumentException("mContext can't be null"); } //如果重新发出服务器请求的时候，需要清除之前的缓存。 if (!cache) { Cache volleyCache = mRequestQueue.getCache(); Cache.Entry cacheEntry = volleyCache.get(url); if (cacheEntry != null) { volleyCache.remove(url); Log.d(TAG, "remove volley cache:" + url); } } mRequestQueue.add(this); } /** * 重写这个方法，可以在http请求头里面加入token，客户端能接受的数据类型 * * @return * @throws AuthFailureError */ @CallSuper @Override public Map<String, String> getHeaders() throws AuthFailureError { Map<String, String> headers = new HashMap<>(); String token = "............"; //headers.put("Authorization", "bearer " + token); //针对Get方法，申明接受的enum类型 // headers.put("Accept", "charset=utf-8"); return headers; } /** * 网络错误问题统一处理 * * @param volleyError * @return */ @CallSuper @Override protected VolleyError parseNetworkError(VolleyError volleyError) { return super.parseNetworkError(volleyError); }} 代码注释比较清晰，就不在赘述。
2.以get方法为例，新建一个GetRequest去继承这个基类，并出解析结果：
public class GetRequest<TResponse> extends AuthenticatedRequestBase<TResponse> { private final Response.Listener<TResponse> listener; private final Class<TResponse> clazz; private final static String TAG = "GetRequest"; private String mUrl; private NetCallback<TResponse> cb; private boolean cacheHit; public GetRequest(String url, Class<TResponse> clazz, boolean cache, NetCallback<TResponse> callback) { super(Request.Method.GET, url, cache, callback.getErrorListener()); this.listener = callback.getSuccessListener(); this.clazz = clazz; this.mUrl = url; this.cb = callback; //无网络时300ms后返回callback if (!NetUtils.isConnect(mContext) && mRequestQueue.getCache().get(url) == null) { Handler handler = new Handler(); handler.postDelayed(new Runnable() { @Override public void run() { cb.OnNetworkOff(); } }, 300); } } /** * 这个是缓存的标记，与本地缓存相关 * @param tag */ @Override public void addMarker(String tag) { super.addMarker(tag); cacheHit = tag.equals("cache-hit"); } @Override protected Response<TResponse> parseNetworkResponse(NetworkResponse response) { Gson gson = new Gson(); //无网络时，使用本地缓存,通过url去匹配缓存，volley sdk是通过url创建不同的文件来实现缓存的 if (!NetUtils.isConnect(mContext) && mRequestQueue.getCache().get(mUrl) != null) { String json = new String(mRequestQueue.getCache().get(mUrl).data); Log.d(TAG, "url==" + mUrl + ",json" + json); cb.fResponseCacheStatus = ResponseCacheStatus.StaleFromCache; return Response.success(gson.fromJson(json, clazz), parseCacheHeaders(response)); } //数据是否有更新 try { if (response.statusCode == 304) { //服务端返回缓存数据 cb.fResponseCacheStatus = ResponseCacheStatus.NotModifiedFromServer; } else if (response.statusCode == 200) { if (cacheHit) { //使用本地缓存 cb.fResponseCacheStatus = ResponseCacheStatus.FreshFromCache; } else { //使用服务端更新数据 cb.fResponseCacheStatus = ResponseCacheStatus.NewFromServer; } } else { cb.fResponseCacheStatus = ResponseCacheStatus.NewFromServer; } Log.d(TAG, "fResponseCacheStatus = " + cb.fResponseCacheStatus); String json = new String(response.data, parseCharset(response.headers)); return Response.success(gson.fromJson(json, clazz), parseCacheHeaders(response)); } catch (UnsupportedEncodingException | JsonSyntaxException e) { return Response.error(new ParseError(e)); } } @Override protected void deliverResponse(TResponse response) { listener.onResponse(response); } @Override protected VolleyError parseNetworkError(VolleyError volleyError) { return super.parseNetworkError(volleyError); }} 3.上面只做了返回成功的处理方式，返回失败时由NetCallback内部统一处理：
@UiThreadpublic abstract class NetCallback<TResponse> { public ResponseCacheStatus fResponseCacheStatus = ResponseCacheStatus.NewFromServer; private String TAG = this.getClass().getSimpleName(); public boolean enableAutomaticToastOnError = true; public NetCallback() { } public NetCallback(boolean enableAutomaticToastOnError) { this.enableAutomaticToastOnError = enableAutomaticToastOnError; } public abstract void OnSuccess(TResponse result); public abstract void OnError(RestfulError error); public void OnNetworkOff() { //do nothing ,use it according to requirement } public Response.Listener<TResponse> getSuccessListener() { return new Response.Listener<TResponse>() { @Override public void onResponse(TResponse result) { OnSuccess(result); } }; } public Response.ErrorListener getErrorListener() { return new Response.ErrorListener() { @Override public void onErrorResponse(VolleyError volleyError) { if (volleyError instanceof TimeoutError) { Log.e(TAG, "networkResponse == null"); //volley TimeoutError OnError(new RestfulError()); } if (volleyError.networkResponse != null) { int statusCode = volleyError.networkResponse.statusCode; String errorMessage = new String(volleyError.networkResponse.data); switch (statusCode) { case 401: //post a Permission authentication failed event break; default: Log.d(TAG, "errorMessage =" + errorMessage); try { RestfulError error = new Gson().fromJson(errorMessage, RestfulError.class); if (enableAutomaticToastOnError && error.getCode() != null) { //toast(error.ExceptionMessage); //toast it in main thread } OnError(error); } catch (Exception e) { OnError(new RestfulError()); Log.d(TAG, "e =" + e.toString()); } break; } } } }; }} 4.注意到没有，在AuthenticatedRequestBase内部有一个环境类YZ,主要负责获取项目主程序中的context和请求队列：
public class YZ implements AppRequestQueue { private static final int DEFAULT_VOLLEY_CACHE_SIZE = 100 * 1024 * 1024; private Context context; private int cacheSize; private YZ() { } @Override public RequestQueue getRequestQueue() { return Volley.newRequestQueue(context, cacheSize); } public Context getContext() { return context; } private static class SingletonHolder { private static YZ instance = new YZ(); } public static YZ getInstance() { return SingletonHolder.instance; } /** * need a app context * * @param appContext */ public void init(final Context appContext) { init(appContext, DEFAULT_VOLLEY_CACHE_SIZE); } /** * @param appContext * @param cacheSize */ public void init(final Context appContext, final int cacheSize) { this.context = appContext; this.cacheSize = cacheSize; }} 这个类需要在app的application中初始化：
public class BaseApp extends Application { public String TAG = this.getClass().getSimpleName(); public static Context applicationContext; public static Executor threadPool; public static final int THREAD_POOL_SIZE = 3; public static final boolean isDebug = BuildConfig.BUILD_TYPE.equals("debug"); @Override public void onCreate() { super.onCreate(); applicationContext = getApplicationContext(); threadPool = Executors.newFixedThreadPool(THREAD_POOL_SIZE); initNet(); } private void initNet() { YZ.getInstance().init(this); } public Context getInstance() { return applicationContext; }} 4.现在可以开始外部封装啦。
public class NewsApi { public static void getInfo(NetCallback<News> callback) { new GetRequest<>(INetConstant.NEWS, News.class, true, callback); }} 还有一点，volley的缓存实现需要服务端配合在http请求的Cache-control: max-age配置支持缓存，并设定好缓存时间，否则无法生效。
最后贴一张效果图:
图片发自简书App
到此结束，后期还会进行优化，代码在[github] (https://github.com/daydaydate/sample)。
总结
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