Android中volley封装实践记录

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：

@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() {
 }

 @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 （本地下载）)。

总结

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