Open codingWang opened 6 years ago
mQueue = Volley.newRequestQueue(context)
主要是 1.建立缓存目录 2.通过版本判断使用HttpURLConnection还是HttpClient,源码及注释如下
public static RequestQueue newRequestQueue(Context context, HttpStack stack) { //缓存目录 File cacheDir = new File(context.getCacheDir(), DEFAULT_CACHE_DIR); String userAgent = "volley/0"; try { String packageName = context.getPackageName(); PackageInfo info = context.getPackageManager().getPackageInfo(packageName, 0); userAgent = packageName + "/" + info.versionCode; } catch (NameNotFoundException e) { } //用哪种Http请求 if (stack == null) { if (Build.VERSION.SDK_INT >= 9) { stack = new HurlStack(); } else { // Prior to Gingerbread, HttpUrlConnection was unreliable. // See: http://android-developers.blogspot.com/2011/09/androids-http-clients.html stack = new HttpClientStack(AndroidHttpClient.newInstance(userAgent)); } } // Network network = new BasicNetwork(stack); //这里初始化了4个网络线程:NetWorkDispatcher数组 RequestQueue queue = new RequestQueue(new DiskBasedCache(cacheDir), network); //start方法内部直接初始化一个CacheDispatcher,循环初始化四个NetWorkDispatcher //并调用线程的start方法开启这五个线程 queue.start(); return queue; }
(1)从缓存队列中提出一个请求对象:final Request<?> request = mCacheQueue.take(); (2)判断是否有缓存(ttl)-->无,放进网络请求队列 (3)判断是否过期-->是,放进网络请求队列 (4)是否需要刷新-->是,放进网络请求队列 (5)回调回去:mDelivery.postResponse(request, response);
(1)取出网络请求对象:request = mQueue.take(); (2)执行请求:mNetwork.performRequest(request); 请求会带上上一次请求的header信息(If-None-Match,If-Modified-Since) 包含对请求超时等异常的处理和retry,如果返回304则更新本地缓存的entry (3)parseNetworkResponse 此为抽象方法,继承Request类实现该方法,做一些预处理 (4)HttpHeaderParser.parseCacheHeaders 解析头部信息,主要是http缓存相关,用于缓存过期判断,产生Cache.Entry对象 (5)回调回去:mDelivery.postResponse(request, response);
Volley对Http304的处理
1.从基本使用说起
1.1 volley的基本使用
1.2 CacheDispatcher线程
1.3 NetWorkDispatcher线程