APP开发关于Volley网络库简介，深圳APP开发公司提醒Volley网络库Volley库是Google官方提供的开源网络库，在Android系统中也使用了这个网络库。Volley库对网络功能进行了封装，默认根据Android系统的不同版本使用不同的HTTP协议栈。
在Android2.3及以上版本使用HurlStack协议栈，在Android2.3以下版本使用HttpClientStack协议栈。使用者也可以自己设置其中使用的HTTP协议栈，使用比较灵活。Volley库支持字符串、图片和JSON格式数据的处理，但因为在解析服务器端的响应消息时，Volley库是把响应消息存储在内存中，所以Volley库不适合大数据量的网络请求，如下载大文件等。在Volley库的Volley类中，提供了设置请求HTTP协议栈的方法。
publicclassVolley{ /**Defaulton-diskcachedirectory.*/ privatestaticfinalStringDEFAULT_CACHE_DIR="volley"; /** *Createsadefaultinstanceoftheworkerpoolandcalls{@linkRequestQueue#start()}onit. * *@paramcontextA{@linkContext}touseforcreatingthecachedir. *@paramstackAn{@linkHttpStack}touseforthenetwork,ornullfordefault. *@returnAstarted{@linkRequestQueue}instance. */ publicstaticRequestQueuenewRequestQueue(Contextcontext,HttpStackstack){ FilecacheDir=newFile(context.getCacheDir(),DEFAULT_CACHE_DIR); StringuserAgent="volley/0"; try{ StringpackageName=context.getPackageName();
PackageInfoinfo=context.getPackageManager().getPackageInfo (packageName,0);userAgent=packageName+"/"+info.versionCode; }catch(NameNotFoundExceptione){ } if(stack==null){ if(Build.VERSION.SDK_INT>=9){ stack=newHurlStack(); }else{ //PriortoGingerbread,HttpUrlConnectionwasunreliable. //See:http://android-developers.blogspot.com/2011/09/androids-http-clients.html stack=newHttpClientStack(AndroidHttpClient.newInstance(userAgent)); } } Networknetwork=newBasicNetwork(stack); RequestQueuequeue=newRequestQueue(newDiskBasedCache(cacheDir),network); queue.start();
returnqueue; } /** *Createsadefaultinstanceoftheworkerpoolandcalls{@linkRequestQueue#start()}onit. * *@paramcontextA{@linkContext}touseforcreatingthecachedir. *@returnAstarted{@linkRequestQueue}instance. */ publicstaticRequestQueuenewRequestQueue(Contextcontext){ returnnewRequestQueue(context,null); }}在Volley库的Request类中，定义了Volley库支持的HTTP方法。publicabstractclassRequest<T>implementsComparable<Request<T>>{ … /** *Supportedrequestmethods. */
publicinterfaceMethod{ intDEPRECATED_GET_OR_POST=-1; intGET=0; intPOST=1; intPUT=2; intDELETE=3; intHEAD=4; intOPTIONS=5; intTRACE=6; intPATCH=7; }… publicRequest(intmethod,Stringurl,Response.ErrorListenerlistener){ mMethod=method; mUrl=url; mIdentifier=createIdentifier(method,url); mErrorListener=listener; setRetryPolicy(newDefaultRetryPolicy()); mDefaultTrafficStatsTag=findDefaultTrafficStatsTag(url); }…}
在Volley库中，HttpHeaderParser类用于处理从服务器获得的头字段数据。publicclassHttpHeaderParser{ publicstaticCache.EntryparseCacheHeaders(NetworkResponseresponse){ longnow=System.currentTimeMillis(); Map<String,String>headers=response.headers; longserverDate=0; longlastModified=0; longserverExpires=0; longsoftExpire=0; longfinalExpire=0; longmaxAge=0; longstaleWhileRevalidate=0; booleanhasCacheControl=false; booleanmustRevalidate=false; StringserverEtag=null; StringheaderValue;
headerValue=headers.get("Date"); if(headerValue!=null){ serverDate=parseDateAsEpoch(headerValue); } headerValue=headers.get("Cache-Control"); if(headerValue!=null){ hasCacheControl=true; String[]tokens=headerValue.split(","); for(inti=0;i<tokens.length;i++){ Stringtoken=tokens[i].trim(); if(token.equals("no-cache")||token.equals("no-store")){ returnnull; }elseif(token.startsWith("max-age=")){ try{ maxAge=Long.parseLong(token.substring(8)); }catch(Exceptione){ } }elseif(token.startsWith("stale-while-revalidate=")){ try{ staleWhileRevalidate=Long.parseLong(token.substring(23)); }catch(Exceptione){
} }elseif(token.equals("must-revalidate")||token.equals("proxy-revalidate")){ mustRevalidate=true; } } } headerValue=headers.get("Expires"); if(headerValue!=null){ serverExpires=parseDateAsEpoch(headerValue); } headerValue=headers.get("Last-Modified"); if(headerValue!=null){ lastModified=parseDateAsEpoch(headerValue); } serverEtag=headers.get("ETag"); //Cache-ControltakesprecedenceoveranExpiresheader,evenifbothexistandExpires //ismorerestrictive. if(hasCacheControl){ softExpire=now+maxAge*1000;
finalExpire=mustRevalidate ?softExpire :softExpire+staleWhileRevalidate*1000; }elseif(serverDate>0&&serverExpires>=serverDate){ //DefaultsemanticforExpireheaderinHTTPspecificationissoftExpire. softExpire=now+(serverExpires-serverDate); finalExpire=softExpire; } Cache.Entryentry=newCache.Entry(); entry.data=response.data; entry.etag=serverEtag; entry.softTtl=softExpire; entry.ttl=finalExpire; entry.serverDate=serverDate; entry.lastModified=lastModified; entry.responseHeaders=headers; returnentry; }…}
目前大多数APP与服务器间传输数据时，都是使用JSON格式，Volley库中提供了使用JSON格式传递数据的类。publicabstractclassJsonRequest<T>extendsRequest{/**DefaultcharsetforJSONrequest.*/protectedstaticfinalStringPROTOCOL_CHARSET="utf-8";/**Contenttypeforrequest.*/privatestaticfinalStringPROTOCOL_CONTENT_TYPE=String.format("application/json;charset=%s",PROTOCOL_CHARSET);privatefinalListener<T>mListener;privatefinalStringmRequestBody; /** *DeprecatedconstructorforaJsonRequestwhichdefaultstoGETunless{@link#getPostBody()} *or{@link#getPostParams()}isoverridden(whichdefaultstoPOST). * *@deprecatedUse{@link#JsonRequest(int,String,String,Listener,ErrorListener)}. */
publicJsonRequest(Stringurl,StringrequestBody,Listener<T>listener, ErrorListenererrorListener){ this(Method.DEPRECATED_GET_OR_POST,url,requestBody,listener,errorListener); } publicJsonRequest(intmethod,Stringurl,StringrequestBody,Listener<T>listener, ErrorListenererrorListener){ super(method,url,errorListener); mListener=listener; mRequestBody=requestBody; } @Override protectedvoiddeliverResponse(Tresponse){ mListener.onResponse(response); } @Override abstractprotectedResponse<T>parseNetworkResponse(NetworkResponseresponse); /**
*@deprecatedUse{@link#getBodyContentType()}. */ @Override publicStringgetPostBodyContentType(){ returngetBodyContentType(); } /** *@deprecatedUse{@link#getBody()}. */ @Override publicbyte[]getPostBody(){ returngetBody(); } @Override publicStringgetBodyContentType(){ returnPROTOCOL_CONTENT_TYPE; } @Override publicbyte[]getBody(){ try{ returnmRequestBody==null?null:mRequestBody.getBytes(PROTOCOL_CHARSET);
}catch(UnsupportedEncodingExceptionuee){ VolleyLog.wtf("UnsupportedEncodingwhiletryingtogetthebytesof%susing%s", mRequestBody,PROTOCOL_CHARSET); returnnull; } }}publicclassJsonObjectRequestextendsJsonRequest<JSONObject>{ /** *Createsanewrequest. *@parammethodtheHTTPmethodtouse *@paramurlURLtofetchtheJSONfrom *@paramjsonRequestA{@linkJSONObject}topostwiththerequest.Nullisallowedand * indicatesnoparameterswillbepostedalongwithrequest. *@paramlistenerListenertoreceivetheJSONresponse *@paramerrorListenerErrorlistener,ornulltoignoreerrors. */ publicJsonObjectRequest(intmethod,Stringurl,JSONObjectjsonRequest, Listener<JSONObject>listener,ErrorListenererrorListener)
errorListener){ super(method,url,(jsonRequest==null)?null:jsonRequest.toString(),listener, errorListener); } /** *Constructorwhichdefaultsto<code>GET</code>if<code>jsonRequest</code>is *<code>null</code>,<code>POST</code>otherwise. * *@see#JsonObjectRequest(int,String,JSONObject,Listener,ErrorListener) */ publicJsonObjectRequest(Stringurl,JSONObjectjsonRequest,Listener<JSONObject>listener, ErrorListenererrorListener){ this(jsonRequest==null?Method.GET:Method.POST,url,jsonRequest, listener,errorListener); } @Override protectedResponse<JSONObject>parseNetworkResponse(NetworkResponseresponse){
try{ StringjsonString=newString(response.data, HttpHeaderParser.parseCharset(response.headers,PROTOCOL_CHARSET)); returnResponse.success(newJSONObject(jsonString), HttpHeaderParser.parseCacheHeaders(response)); }catch(UnsupportedEncodingExceptione){ returnResponse.error(newParseError(e)); }catch(JSONExceptionje){ returnResponse.error(newParseError(je)); } }}
好了，APP开发公司本文关于“开发APP关于Volley库支持的HTTP方法与代码分享”就到这里，谢谢关注，希望能给您的APP开发前期工作有所帮助，博纳网络编辑整理。
