volley7--NetworkDispatcher从网络中获取数据

 ?1 /* ?2 ?* Copyright (C) 2011 The Android Open Source Project ?3 ?* ?4 ?* Licensed under the Apache License, Version 2.0 (the "License"); ?5 ?* you may not use this file except in compliance with the License. ?6 ?* You may obtain a copy of the License at ?7 ?* ?8 ?* ?????http://www.apache.org/licenses/LICENSE-2.0 ?9 ?* 10 ?* Unless required by applicable law or agreed to in writing, software 11 ?* distributed under the License is distributed on an "AS IS" BASIS, 12 ?* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 ?* See the License for the specific language governing permissions and 14 ?* limitations under the License. 15 ?*/ 16 ?17 package com.android.volley; 18 ?19 import android.annotation.TargetApi; 20 import android.net.TrafficStats; 21 import android.os.Build; 22 import android.os.Process; 23 import android.os.SystemClock; 24 ?25 import java.util.concurrent.BlockingQueue; 26 ?27 /** 28 ?* Provides a thread for performing network dispatch from a queue of requests. 29 ?* 30 ?* Requests added to the specified queue are processed from the network via a 31 ?* specified {@link Network} interface. Responses are committed to cache, if 32 ?* eligible, using a specified {@link Cache} interface. Valid responses and 33 ?* errors are posted back to the caller via a {@link ResponseDelivery}. 34 ?*/ 35 public class NetworkDispatcher extends Thread { 36 ????/** The queue of requests to service. */ 37 ????private final BlockingQueue<Request<?>> mQueue; 38 ????/** The network interface for processing requests. */ 39 ????private final Network mNetwork; 40 ????/** The cache to write to. */ 41 ????private final Cache mCache; 42 ????/** For posting responses and errors. */ 43 ????private final ResponseDelivery mDelivery; 44 ????/** Used for telling us to die. */ 45 ????private volatile boolean mQuit = false; 46 ?47 ????/** 48 ?????* Creates a new network dispatcher thread. ?You must call {@link #start()} 49 ?????* in order to begin processing. 50 ?????* 51 ?????* @param queue Queue of incoming requests for triage 52 ?????* @param network Network interface to use for performing requests 53 ?????* @param cache Cache interface to use for writing responses to cache 54 ?????* @param delivery Delivery interface to use for posting responses 55 ?????*/ 56 ????public NetworkDispatcher(BlockingQueue<Request<?>> queue, 57 ????????????Network network, Cache cache, 58 ????????????ResponseDelivery delivery) { 59 ????????mQueue = queue; 60 ????????mNetwork = network; 61 ????????mCache = cache; 62 ????????mDelivery = delivery; 63 ????} 64 ?65 ????/** 66 ?????* Forces this dispatcher to quit immediately. ?If any requests are still in 67 ?????* the queue, they are not guaranteed to be processed. 68 ?????*/ 69 ????public void quit() { 70 ????????mQuit = true; 71 ????????interrupt(); 72 ????} 73 ?74 ????@TargetApi(Build.VERSION_CODES.ICE_CREAM_SANDWICH) 75 ????private void addTrafficStatsTag(Request<?> request) { 76 ????????// Tag the request (if API >= 14) 77 ????????if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH) { 78 ????????????TrafficStats.setThreadStatsTag(request.getTrafficStatsTag()); 79 ????????} 80 ????} 81 ?82 ????@Override 83 ????public void run() { 84 ????????Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND); 85 ????????Request<?> request; 86 ????????while (true) { 87 ????????????long startTimeMs = SystemClock.elapsedRealtime(); 88 ????????????// release previous request object to avoid leaking request object when mQueue is drained. 89 ????????????request = null; 90 ????????????try { 91 ????????????????// Take a request from the queue. 92 ????????????????request = mQueue.take(); 93 ????????????} catch (InterruptedException e) { 94 ????????????????// We may have been interrupted because it was time to quit. 95 ????????????????if (mQuit) { 96 ????????????????????return; 97 ????????????????} 98 ????????????????continue; 99 ????????????}100 101 ????????????try {102 ????????????????request.addMarker("network-queue-take");103 104 ????????????????// If the request was cancelled already, do not perform the105 ????????????????// network request.106 ????????????????if (request.isCanceled()) {107 ????????????????????request.finish("network-discard-cancelled");108 ????????????????????continue;109 ????????????????}110 111 ????????????????addTrafficStatsTag(request);112 113 ????????????????// Perform the network request.114 ????????????????NetworkResponse networkResponse = mNetwork.performRequest(request);115 ????????????????request.addMarker("network-http-complete");116 117 ????????????????// If the server returned 304 AND we delivered a response already,118 ????????????????// we‘re done -- don‘t deliver a second identical response.119 ????????????????if (networkResponse.notModified && request.hasHadResponseDelivered()) {120 ????????????????????request.finish("not-modified");121 ????????????????????continue;122 ????????????????}123 124 ????????????????// Parse the response here on the worker thread.125 ????????????????Response<?> response = request.parseNetworkResponse(networkResponse);126 ????????????????request.addMarker("network-parse-complete");127 128 ????????????????// Write to cache if applicable.129 ????????????????// TODO: Only update cache metadata instead of entire record for 304s.130 ????????????????if (request.shouldCache() && response.cacheEntry != null) {131 ????????????????????mCache.put(request.getCacheKey(), response.cacheEntry);132 ????????????????????request.addMarker("network-cache-written");133 ????????????????}134 135 ????????????????// Post the response back.136 ????????????????request.markDelivered();137 ????????????????mDelivery.postResponse(request, response);138 ????????????} catch (VolleyError volleyError) {139 ????????????????volleyError.setNetworkTimeMs(SystemClock.elapsedRealtime() - startTimeMs);140 ????????????????parseAndDeliverNetworkError(request, volleyError);141 ????????????} catch (Exception e) {142 ????????????????VolleyLog.e(e, "Unhandled exception %s", e.toString());143 ????????????????VolleyError volleyError = new VolleyError(e);144 ????????????????volleyError.setNetworkTimeMs(SystemClock.elapsedRealtime() - startTimeMs);145 ????????????????mDelivery.postError(request, volleyError);146 ????????????}147 ????????}148 ????}149 150 ????private void parseAndDeliverNetworkError(Request<?> request, VolleyError error) {151 ????????error = request.parseNetworkError(error);152 ????????mDelivery.postError(request, error);153 ????}154 }