public Request Add(Request request)
{
request.SetRequestQueue(this);
//添加到当前请求列表中
lock (mCurrentRequests)
{
mCurrentRequests.Add(request);
}
request.Sequence = GetSequenceNumber();
request.AddMarker("add-to-queue");
//如果请求不需要缓存则直接加入到网络请求队列中
if (!request.ShouldCache())
{
mNetworkQueue.Enqueue(request);
return(request);
}
/*
* 先将请求加入到缓存请求队列中，并且将后面的重复请求
* 添加到mWaitingRequests中，目的是当第一个请求完成后
* 后面重复的请求直接添加到缓存请求队列中，避免重复对
* 网络进行请求
*/
lock (mWaitingRequests)
{
String cacheKey = request.GetCacheKey();
if (mWaitingRequests.ContainsKey(cacheKey))
{
Queue <Request> stagedRequests = null;
mWaitingRequests.TryGetValue(cacheKey, out stagedRequests);
if (stagedRequests == null)
{
stagedRequests = new Queue <Request>();
}
stagedRequests.Enqueue(request);
if (VolleyLog.DEBUG)
{
VolleyLog.V("Request for cacheKey={0} is in flight,putting on hold.", cacheKey);
}
}
else
{
mWaitingRequests.Add(cacheKey, null);
mCacheQueue.Enqueue(request);
}
return(request);
}
}
/// <summary>
/// 当需要的空间大于指定空间后清除部分缓存
/// </summary>
private void PruneIfNeeded(int neededSpace)
{
if (mTotalSize + neededSpace < mMaxCacheSizeInBytes)
{
return;
}
if (VolleyLog.DEBUG)
{
VolleyLog.V("Pruning old cache entries.");
}
long before = mTotalSize;
int prunedFiles = 0;
long startTime = SystemClock.ElapsedRealtime();
Dictionary <string, CacheHeader> delDic = new Dictionary <string, CacheHeader>();
foreach (KeyValuePair <String, CacheHeader> pair in mEntries)
{
CacheHeader e = pair.Value;
var fi = GetFileForKey(e.Key);
fi.Delete();
if (!File.Exists(fi.FullName))
{
mTotalSize -= e.Size;
}
else
{
VolleyLog.D("Could not delete cache entry for key={0},filename={1}", e.Key, GetFilenameForKey(e.Key));
}
prunedFiles++;
delDic.Add(pair.Key, pair.Value);
if (mTotalSize + neededSpace < mMaxCacheSizeInBytes * HYSTERESIS_FACTOR)
{
break;
}
}
foreach (KeyValuePair <string, CacheHeader> del in delDic)
{
mEntries.Remove(del.Key);
}
if (VolleyLog.DEBUG)
{
VolleyLog.V("Pruned {0} files,{1} bytes,{2} ms", prunedFiles, (mTotalSize - before), SystemClock.ElapsedRealtime() - startTime);
}
}
public void Finish(Request request)
{
lock (mCurrentRequests)
{
mCurrentRequests.Remove(request);
}
lock (mFinishedListeners)
{
foreach (IRequestFinishedListener listener in mFinishedListeners)
{
listener.OnRequestFinished(request);
}
}
if (request.ShouldCache())
{
/*
* 在该请求完成并缓存后将后面其他重复的
* 请求直接加入到缓存请求队列中
*/
lock (mWaitingRequests)
{
String cacheKey = request.GetCacheKey();
Queue <Request> waitingRequets = null;
mWaitingRequests.TryGetValue(cacheKey, out waitingRequets);
mWaitingRequests.Remove(cacheKey);
if (waitingRequets != null)
{
if (VolleyLog.DEBUG)
{
VolleyLog.V("Releasing {0} waiting requests for cacheKey={1}", waitingRequets.Count, cacheKey);
}
foreach (Request addrequest in waitingRequets)
{
mCacheQueue.Enqueue(addrequest);
}
}
}
}
}
public override void Run()
{
if (DEBUG)
{
VolleyLog.V("start new dispatcher");
}
Process.SetThreadPriority(ThreadPriority.Background);
mCache.Initialize();
while (true)
{
try
{
Request request = null;
if (!mCacheQueue.TryDequeue(out request))
{
if (mQuit)
{
return;
}
continue;
}
request.AddMarker("cache-queue-take");
//请求是否已取消
if (request.IsCanceled)
{
request.Finish("cache-discard-canceled");
continue;
}
//不存在该缓存
Entry entry = mCache.Get(request.GetCacheKey());
if (entry == null)
{
request.AddMarker("cache-miss");
mNetworkQueue.Enqueue(request);
continue;
}
//缓存过期
if (entry.IsExpired)
{
request.AddMarker("cache-hit-expired");
request.CacheEntry = entry;
mNetworkQueue.Enqueue(request);
continue;
}
//缓存命中
request.AddMarker("cache-hit");
Response response = request.ParseNetworkResponse(new NetworkResponse(entry.Data, entry.ResponseHeaders));
request.AddMarker("cache-hit-parsed");
//判断缓存是否需要更新
if (!entry.RefreshNeeded())
{
mDelivery.PostResponse(request, response);
}
else
{
request.AddMarker("cache-hit-refresh-needed");
request.CacheEntry = entry;
response.Intermediate = true;
mDelivery.PostResponse(request, response, () =>
{
mNetworkQueue.Enqueue(request);
});
}
}
catch (Exception)
{
if (mQuit)
{
return;
}
continue;
}
}
}
protected void LogError(String what, String url, long start)
{
long now = SystemClock.ElapsedRealtime();
VolleyLog.V("HTTP ERROR({0}) {1} ms to fetch {2}", what, (now - start), url);
}
