Android volley封装实践

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。
”’
private void volley_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，假如你觉得然并软即可以左滑退出了。（我的文章有左滑自动关注效果哈哈）

”’
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，用来创立一个新的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;

/** * 创立新的请求，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");    }    //假如重新发出服务器请求的时候，需要清理之前的缓存。    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，用户端能接受的数据类型 * * @return * @throws AuthFailureError */@CallSuper@Overridepublic 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;}/** * 网络错误问题统一解决 * * @param volleyError * @return */@CallSuper@Overrideprotected 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 */@Overridepublic void addMarker(String tag) {    super.addMarker(tag);    cacheHit = tag.equals("cache-hit");}@Overrideprotected 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创立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));    }    //数据能否有升级    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 {                //使用服务端升级数据                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));    }}@Overrideprotected void deliverResponse(TResponse response) {    listener.onResponse(response);}@Overrideprotected VolleyError parseNetworkError(VolleyError volleyError) {    return super.parseNetworkError(volleyError);}

}
”’
3.上面只做了返回成功的解决方式，返回失败时由NetCallback内部统一解决：
”’
@UiThread
public 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() {}@Overridepublic 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");@Overridepublic 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:

到此结束，后期还会进行优化，代码在 daydaydate/sample。感谢阅读，觉得不错的话点赞哦！