@SuppressWarnings("unchecked")
    @Override
    public void run() {
      // If this request has canceled, finish it and don't deliver.
      if (mRequest.isCanceled()) {
        mRequest.finish("canceled-at-delivery");
        return;
      }

      // Deliver a normal response or error, depending.
      if (mResponse.isSuccess()) {
        mRequest.deliverResponse(mResponse.result);
      } else {
        mRequest.deliverError(mResponse.error);
      }

      // If this is an intermediate response, add a marker, otherwise we're done
      // and the request can be finished.
      if (mResponse.intermediate) {
        mRequest.addMarker("intermediate-response");
      } else {
        mRequest.finish("done");
      }

      // If we have been provided a post-delivery runnable, run it.
      if (mRunnable != null) {
        mRunnable.run();
      }
    }
  /**
   * Adds a Request to the dispatch queue.
   *
   * @param request The request to service
   * @return The passed-in request
   */
  public <T> Request<T> add(Request<T> request) {
    // Tag the request as belonging to this queue and add it to the set of
    // current requests.
    request.setRequestQueue(this);
    synchronized (mCurrentRequests) {
      mCurrentRequests.add(request);
    }

    // Process requests in the order they are added.
    request.setSequence(getSequenceNumber());
    request.addMarker("add-to-queue");

    // If the request is uncacheable, skip the cache queue and go straight
    // to the network.
    if (!request.shouldCache()) {
      mNetworkQueue.add(request);
      return request;
    }

    // Insert request into stage if there's already a request with the same
    // cache key in flight.
    synchronized (mWaitingRequests) {
      String cacheKey = request.getCacheKey();
      if (mWaitingRequests.containsKey(cacheKey)) {
        // There is already a request in flight. Queue up.
        Queue<Request<?>> stagedRequests = mWaitingRequests.get(cacheKey);
        if (stagedRequests == null) {
          stagedRequests = new LinkedList<Request<?>>();
        }
        stagedRequests.add(request);
        mWaitingRequests.put(cacheKey, stagedRequests);
        if (VolleyLog.DEBUG) {
          VolleyLog.v("Request for cacheKey=%s is in flight, putting on hold.", cacheKey);
        }
      } else {
        // Insert 'null' queue for this cacheKey, indicating there is
        // now a request in
        // flight.
        mWaitingRequests.put(cacheKey, null);
        mCacheQueue.add(request);
      }
      return request;
    }
  }
  @Override
  public void run() {
    if (DEBUG) VolleyLog.v("start new dispatcher");
    Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND);

    // Make a blocking call to initialize the cache.
    if (mCache != null) {
      mCache.initialize();
    }

    while (true) {
      try {
        // Get a request from the cache triage queue, blocking until
        // at least one is available.
        final Request<?> request = mCacheQueue.take();
        request.addMarker("cache-queue-take");
        mDelivery.postPreExecute(request);

        // If the request has been canceled, don't bother dispatching
        // it.
        if (request.isCanceled()) {
          request.finish("cache-discard-canceled");
          mDelivery.postCancel(request);
          mDelivery.postFinish(request);
          continue;
        }

        // Attempt to retrieve this item from cache.
        DiskCache.Entry entry = mCache != null ? mCache.getEntry(request.getCacheKey()) : null;
        if (entry == null) {
          request.addMarker("cache-miss");
          // Cache miss; send off to the network dispatcher.
          mNetworkQueue.put(request);
          mDelivery.postNetworking(request);
          continue;
        }

        // If it is completely expired, just send it to the network.
        if (entry.isExpired()) {
          request.addMarker("cache-hit-expired");
          request.setCacheEntry(entry);
          mNetworkQueue.put(request);
          mDelivery.postNetworking(request);
          continue;
        }

        // We have a cache hit; parse its data for delivery back to the
        // request.
        request.addMarker("cache-hit");
        Response<?> response =
            request.parseNetworkResponse(new NetworkResponse(entry.data, entry.responseHeaders));
        request.addMarker("cache-hit-parsed");
        mDelivery.postUsedCache(request);

        if (!entry.refreshNeeded()) {
          // Completely unexpired cache hit. Just deliver the
          // response.
          mDelivery.postResponse(request, response);
        } else {
          // Soft-expired cache hit. We can deliver the cached
          // response,
          // but we need to also send the request to the network for
          // refreshing.
          request.addMarker("cache-hit-refresh-needed");
          request.setCacheEntry(entry);

          // Mark the response as intermediate.
          response.intermediate = true;

          // Post the intermediate response back to the user and have
          // the delivery then forward the request along to the
          // network.
          mDelivery.postResponse(
              request,
              response,
              new Runnable() {
                @Override
                public void run() {
                  try {
                    mNetworkQueue.put(request);
                  } catch (InterruptedException e) {
                    // Not much we can do about this.
                  }
                }
              });
        }
      } catch (InterruptedException e) {
        // We may have been interrupted because it was time to quit.
        if (mQuit) {
          return;
        }
        continue;
      }
    }
  }
  @Override
  public void run() {
    Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND);
    Request<?> request;
    while (true) {
      try {
        // Take a request from the queue.
        request = mQueue.take();
      } catch (InterruptedException e) {
        // We may have been interrupted because it was time to quit.
        if (mQuit) {
          return;
        }
        continue;
      }

      try {
        request.addMarker("network-queue-take");

        // If the request was cancelled already, do not perform the
        // network request.
        if (request.isCanceled()) {
          request.finish("network-discard-cancelled");
          continue;
        }

        addTrafficStatsTag(request);

        // Perform the network request.
        NetworkResponse networkResponse = mNetwork.performRequest(request);
        request.addMarker("network-http-complete");

        // If the server returned 304 AND we delivered a response already,
        // we're done -- don't deliver a second identical response.
        if (networkResponse.notModified && request.hasHadResponseDelivered()) {
          request.finish("not-modified");
          continue;
        }

        // Parse the response here on the worker thread.
        Response<?> response = request.parseNetworkResponse(networkResponse);
        request.addMarker("network-parse-complete");

        // Write to cache if applicable.
        // TODO: Only update cache metadata instead of entire record for 304s.
        if (request.shouldCache() && response.cacheEntry != null) {
          mCache.put(request.getCacheKey(), response.cacheEntry);
          request.addMarker("network-cache-written");
        }

        // Post the response back.
        request.markDelivered();
        mDelivery.postResponse(request, response);
      } catch (VolleyError volleyError) {
        parseAndDeliverNetworkError(request, volleyError);
      } catch (Exception e) {
        VolleyLog.e(e, "Unhandled exception %s", e.toString());
        mDelivery.postError(request, new VolleyError(e));
      }
    }
  }
 @Override
 public void postError(Request<?> request, VolleyError error) {
   request.addMarker("post-error");
   Response<?> response = Response.error(error);
   mResponsePoster.execute(new ResponseDeliveryRunnable(request, response, null));
 }
 @Override
 public void postResponse(Request<?> request, Response<?> response, Runnable runnable) {
   request.markDelivered();
   request.addMarker("post-response");
   mResponsePoster.execute(new ResponseDeliveryRunnable(request, response, runnable));
 }