Volley 源碼解讀
Volley 的中文翻譯為“齊射、并發(fā)”，是在2013年的Google大會上發(fā)布的一款A(yù)ndroid平臺網(wǎng)絡(luò)通信庫，具有網(wǎng)絡(luò)請求的處理、小圖片的異步加載和緩存等功能，能夠幫助 Android APP 更方便地執(zhí)行網(wǎng)絡(luò)操作，而且更快速高效。Volley可是說是把AsyncHttpClient和Universal-Image-Loader的優(yōu)點(diǎn)集于了一身，既可以像AsyncHttpClient一樣非常簡單地進(jìn)行HTTP通信，也可以像Universal-Image-Loader一樣輕松加載網(wǎng)絡(luò)上的圖片。除了簡單易用之外，Volley在性能方面也進(jìn)行了大幅度的調(diào)整，它的設(shè)計(jì)目標(biāo)就是非常適合去進(jìn)行數(shù)據(jù)量不大，但通信頻繁的網(wǎng)絡(luò)操作，而對于大數(shù)據(jù)量的網(wǎng)絡(luò)操作，比如說下載文件等，Volley的表現(xiàn)就會非常糟糕。
在Google IO的演講上，其配圖是一幅發(fā)射火弓箭的圖，有點(diǎn)類似流星。這表示，Volley特別適合數(shù)據(jù)量不大但是通信頻繁的場景。見下圖：
目錄
-
[Volley特點(diǎn)]
-
[Volley執(zhí)行流程]
-
[Volley初始化]
-
[創(chuàng)建RequestQueue]
- [DiskBasedCache]
-
[CacheDispatcher & NetworkDispatcher]
-
[Request]
-
[加入RequestQueue]
-
[Request#finish自己]
-
[取消請求]
-
[緩存處理]
-
[Request請求失敗重試機(jī)制]
-
[PoolingByteArrayOutputStream & ByteArrayPool]
-
[Volley加載圖片 ]
-
[Handler]
-
[volley gson改造 ]
- [volley okhttp改造]
Volley特點(diǎn)
-
自動(dòng)調(diào)度網(wǎng)絡(luò)請求；
- Volley直接new 5個(gè)線程（默認(rèn)5個(gè)），讓多個(gè)線程去搶奪網(wǎng)絡(luò)請求對象（Request），搶到就執(zhí)行，搶不到就等待，直到有網(wǎng)絡(luò)請求到來。
-
可以加載圖片；
-
通過標(biāo)準(zhǔn)的 HTTP cache coherence（高速緩存一致性）緩存磁盤和內(nèi)存透明的響應(yīng)；
-
支持指定請求的優(yōu)先級；
- 根據(jù)優(yōu)先級去請求數(shù)據(jù)
- 網(wǎng)絡(luò)請求cancel機(jī)制。我們可以取消單個(gè)請求，或者指定取消請求隊(duì)列中的一個(gè)區(qū)域；
- 例如Activity finish后結(jié)束請求
- 框架容易被定制，例如，定制重試或者網(wǎng)絡(luò)請求庫；
- 例如基于Okhttp的Volley
Volley執(zhí)行流程
Volley初始化
創(chuàng)建RequestQueue
使用Volley時(shí)我們需要先創(chuàng)建一個(gè)RequestQueue，如下
RequestQueue queue = Volley.newRequestQueue(context);Volley.newRequestQueue(context)最終調(diào)用了如下方法
public static RequestQueue newRequestQueue(Context context, HttpStack stack) {
File cacheDir = new File(context.getCacheDir(), DEFAULT_CACHE_DIR);
...
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);
RequestQueue queue = new RequestQueue(new DiskBasedCache(cacheDir), network);
queue.start();
return queue;
}
HttpStack 是一個(gè)接口，主要用于請求網(wǎng)絡(luò)數(shù)據(jù)，并返回結(jié)果。默認(rèn)情況下stack是null，
當(dāng)android版本>=9時(shí)使用HurlStack，否則使用HttpClientStack
若用戶想要使用其他的網(wǎng)絡(luò)請求類庫，比如okhttp等就可以實(shí)現(xiàn)HttpStack接口，并在
HttpResponse performRequest(Request request, Map additionalHeaders)
throws IOException, AuthFailureError 中調(diào)用okhttp進(jìn)行網(wǎng)絡(luò)請求，并把請求的結(jié)果封裝成一個(gè)
HttpResponse返回即可，HttpResponse中包含了狀態(tài)碼，響應(yīng)頭，body信息。
newRequestQueue中創(chuàng)建了一個(gè)BasicNetwork對象，BasicNetwork使用HttpStack執(zhí)行網(wǎng)絡(luò)請求，成功后返回一個(gè)NetworkResponse,NetworkResponse只是一個(gè)簡單的記錄狀態(tài)碼，body，響應(yīng)頭，服務(wù)端是否返回304并且緩存過，執(zhí)行網(wǎng)絡(luò)請求時(shí)間的類。
DiskBasedCache
newRequestQueue 中還創(chuàng)建了一個(gè) RequestQueue，RequestQueue 中持有一個(gè) DiskBasedCache 對象，DiskBasedCache 是把服務(wù)端返回的數(shù)據(jù)保持到本地文件中的類，默認(rèn)大小5M。
緩存文件是一個(gè)二進(jìn)制文件，非文本文件，
緩存文件的開頭有個(gè)特殊的整型魔數(shù)（CACHE_MAGIC），用于判斷是不是緩存文件。DiskBasedCache 初始化時(shí)會
讀取特定文件夾下的所有文件的部分?jǐn)?shù)據(jù)，包括響應(yīng)頭等極少數(shù)數(shù)據(jù)，不包含body，當(dāng)調(diào)用DiskBasedCache的get（String key）方法時(shí)才讀取body部分，若文件開頭魔數(shù)不是 CACHE_MAGIC 則刪除。是的話就把讀取的數(shù)據(jù)保存到內(nèi)存中。代碼如下
public synchronized void initialize() {
if (!mRootDirectory.exists()) {
return;
}
File[] files = mRootDirectory.listFiles();
if (files == null) {
return;
}
for (File file : files) {
BufferedInputStream fis = null;
try {
fis = new BufferedInputStream(new FileInputStream(file));
CacheHeader entry = CacheHeader.readHeader(fis);
entry.size = file.length();
putEntry(entry.key, entry);
} catch (IOException e) {
if (file != null) {
file.delete();
}
} finally {
try {
if (fis != null) {
fis.close();
}
} catch (IOException ignored) { }
}
}
}緩存文件除了可以保存 int，long 型數(shù)據(jù)，還可以保存 String 字符串，Map
保存 Map
static String readString(InputStream is) throws IOException {
int n = (int) readLong(is);
byte[] b = streamToBytes(is, n);
return new String(b, "UTF-8");
}
static Map readStringStringMap(InputStream is) throws IOException {
int size = readInt(is);
Map result = (size == 0)
? Collections.emptyMap()
: new HashMap(size);
for (int i = 0; i < size; i++) {
String key = readString(is).intern();
String value = readString(is).intern();
result.put(key, value);
}
return result;
}
static long readLong(InputStream is) throws IOException {
long n = 0;
n |= ((read(is) & 0xFFL) << 0);
n |= ((read(is) & 0xFFL) << 8);
n |= ((read(is) & 0xFFL) << 16);
n |= ((read(is) & 0xFFL) << 24);
n |= ((read(is) & 0xFFL) << 32);
n |= ((read(is) & 0xFFL) << 40);
n |= ((read(is) & 0xFFL) << 48);
n |= ((read(is) & 0xFFL) << 56);
return n;
}
緩存文件名由cache key字符串的前半段字符串的hashCode拼接上cache key（網(wǎng)絡(luò)請求url）后
半段字符串的hashCode值組成。代碼如下
private String getFilenameForKey(String key) {
int firstHalfLength = key.length() / 2;
String localFilename = String.valueOf(key.substring(0, firstHalfLength).hashCode());
localFilename += String.valueOf(key.substring(firstHalfLength).hashCode());
return localFilename;
}當(dāng)緩存文件占用空間超過指定值時(shí)，Volley只是簡單的刪除的部分文件，刪除代碼如下
private void pruneIfNeeded(int neededSpace) {
if ((mTotalSize + neededSpace) < mMaxCacheSizeInBytes) {
return;
}
Iterator> iterator = mEntries.entrySet().iterator();
while (iterator.hasNext()) {
Map.Entry entry = iterator.next();
CacheHeader e = entry.getValue();
boolean deleted = getFileForKey(e.key).delete();
if (deleted) {
mTotalSize -= e.size;
}
iterator.remove();
if ((mTotalSize + neededSpace) < mMaxCacheSizeInBytes * 0.9f) {
break;
}
}
} 可以看到刪除時(shí)只是遍歷mEntries，如果刪除成功并且剩余文件所占大小+新的緩存所需空間
CacheDispatcher & NetworkDispatcher
RequestQueue 只是一個(gè)普通的類，沒有繼承任何類，RequestQueue 的 start 方法中創(chuàng)建了一個(gè) CacheDispatcher，和4個(gè)（默認(rèn)4個(gè)）NetworkDispatcher，
CacheDispatcher 和 NetworkDispatcher 都是 Thread 的直接子類，這5個(gè) Thread 就是前面提到的搶奪網(wǎng)絡(luò)請求對象的 Thread。
調(diào)用start()時(shí)先調(diào)用了一下stop()，stop()中把5個(gè)線程的mQuit設(shè)為 true，然后調(diào)用interrupt()讓 Thread 的run不再執(zhí)行。
代碼如下
public void start() {
stop(); // Make sure any currently running dispatchers are stopped.
// Create the cache dispatcher and start it.
mCacheDispatcher = new CacheDispatcher(mCacheQueue, mNetworkQueue, mCache, mDelivery);
mCacheDispatcher.start();
// Create network dispatchers (and corresponding threads) up to the pool size.
for (int i = 0; i < mDispatchers.length; i++) {
NetworkDispatcher networkDispatcher = new NetworkDispatcher(mNetworkQueue, mNetwork,
mCache, mDelivery);
mDispatchers[i] = networkDispatcher;
networkDispatcher.start();
}
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();
...
}
}
}
/**
* Stops the cache and network dispatchers.
*/
public void stop() {
if (mCacheDispatcher != null) {
mCacheDispatcher.quit();
}
for (int i = 0; i < mDispatchers.length; i++) {
if (mDispatchers[i] != null) {
mDispatchers[i].quit();
}
}
}CacheDispatcher啟動(dòng)后先調(diào)用了一下DiskBasedCache的initialize()方法，這個(gè)方法要讀取文件，比較耗時(shí)，Volley把他放到了Cache線程中。
CacheDispatcher和NetworkDispatcher的run方法內(nèi)部很像，都是在 while (true)循環(huán)中從PriorityBlockingQueue中讀取Request，CacheDispatcher 獨(dú)享一個(gè)PriorityBlockingQueue，其余4各 NetworkDispatcher 共享一個(gè)PriorityBlockingQueue 。PriorityBlockingQueue是一個(gè)阻塞隊(duì)列，當(dāng)隊(duì)列里沒有Request時(shí)take()方法就會阻塞，直到有Request到來，PriorityBlockingQueue是線程安全的
同一個(gè) Request 只能被1個(gè)線程獲取到。PriorityBlockingQueue 可以根據(jù)線程優(yōu)先級對隊(duì)列里的reqest進(jìn)行排序。
Volley 的初始化到這就完成了，下面開始執(zhí)行網(wǎng)絡(luò)請求
Request
使用 Volley 進(jìn)行網(wǎng)絡(luò)請求時(shí)我們要把請求封裝成一個(gè) Request 對象，包括url，請求參數(shù)，請求成功失敗 Listener，
Volley 默認(rèn)給我們提供了 ImageRequest（獲取圖片），
JsonObjectRequest、JsonArrayRequest（獲取json），StringRequest（獲取 String）。
例如：
Requestrequest=new StringRequest(Method.GET, "http://mogujie.com", new Listener(){
@Override
public void onResponse(String response) {
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
}
});
Volley.newRequestQueue(context).add(request); 只需要把Request丟進(jìn)requestQueue中就可以。
加入RequestQueue
我們來看一下add方法：
public Request add(Request 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> stagedRequests = mWaitingRequests.get(cacheKey);
if (stagedRequests == null) {
stagedRequests = new LinkedList>();
}
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;
}
}
add方法中首先設(shè)置了request所在的請求隊(duì)列，為了在用戶取消請求時(shí)能夠把request從requestQueue中移除掉。
接下來設(shè)置了一下request的序列號，序列號按添加順序依次從0開始編號，同一個(gè)隊(duì)列中任何兩個(gè)request的序列號都不相同。序列號可以影響request的優(yōu)先級。
request.addMarker("")用于調(diào)試（打印日志等）。
通過查看源碼我們可以看到request默認(rèn)是需要緩存的。
/** Whether or not responses to this request should be cached. */
private boolean mShouldCache = true;若request不需要緩存則直接把request丟到mNetworkQueue，然后4個(gè) NetworkDispatcher 就可以"搶奪"request了，誰"搶"到誰就執(zhí)行網(wǎng)絡(luò)請求
如需要緩存則先判斷一下mWaitingRequests中有沒有正在請求的相同的request（根據(jù)request的url判斷），沒有的話就把該request丟到mCacheQueue中，
這樣 CacheDispatcher 執(zhí)行完之前的請求后就可以執(zhí)行該request了，若已經(jīng)有相同的request正在執(zhí)行，則只需保存一下該request，
等相同的request執(zhí)行完后直接使用其結(jié)果就可。
CacheDispatcher中獲取到request后先判斷一下request后有沒有取消，有的話就finish掉自己，然后等待下一個(gè)request的到來
if (request.isCanceled()) {
request.finish("cache-discard-canceled");
continue;
}接下來會從緩存中取緩存，沒有或者緩存已經(jīng)過期，就把request丟掉mNetworkQueue中，讓NetworkDisptcher去“搶奪”request
// Attempt to retrieve this item from cache.
Cache.Entry entry = mCache.get(request.getCacheKey());
if (entry == null) {
request.addMarker("cache-miss");
// Cache miss; send off to the network dispatcher.
mNetworkQueue.put(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);
continue;
}若取到緩存且沒過期，則解析緩存
Response response = request.parseNetworkResponse(
new NetworkResponse(entry.data, entry.responseHeaders));
若不需要刷新則把request和response丟到ui線程中，回調(diào)request中的請求成功或失敗listener，同時(shí)finish自己
若還需要刷新的話還需要把request丟到mNetworkQueue中，讓NetworkDispatcher去獲取數(shù)據(jù)。
NetworkDispatcher在獲取到數(shù)據(jù)后執(zhí)行了如下代碼：
// 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");
}CacheDispatcher 才是處理緩存相關(guān)的，為什么 NetworkDispatcher 中還需要進(jìn)行以上的判斷呢？
Request#finish自己
前面我們提到過 CacheDispatcher 把相同的request放到了隊(duì)列中，當(dāng)獲取到數(shù)據(jù)后調(diào)用了request的finish方法，該方法又調(diào)用了
mRequestQueue的finish方法。
void finish(final String tag) {
if (mRequestQueue != null) {
mRequestQueue.finish(this);
}
...
}request的finish方法如下：
void finish(Request request) {
...
if (request.shouldCache()) {
synchronized (mWaitingRequests) {
String cacheKey = request.getCacheKey();
Queue> waitingRequests = mWaitingRequests.remove(cacheKey);
if (waitingRequests != null) {
if (VolleyLog.DEBUG) {
VolleyLog.v("Releasing %d waiting requests for cacheKey=%s.",
waitingRequests.size(), cacheKey);
}
// Process all queued up requests. They won't be considered as in flight, but
// that's not a problem as the cache has been primed by 'request'.
mCacheQueue.addAll(waitingRequests);
}
}
}
}
}
finish中取出了相同的request所在的隊(duì)列，然后把請求丟到了mCacheQueue中，丟到mCacheQueue后就會導(dǎo)致 CacheDispatcher 去執(zhí)行網(wǎng)絡(luò)請求，
這時(shí)由于上次的請求已經(jīng)緩存了，所以可以直接使用上傳的數(shù)據(jù)了，到此為止request如何finish自己就介紹完了。
取消請求
我們可以調(diào)用request.cancel取消某個(gè)請求，也可以調(diào)用requestQueue的 cancelAll(RequestFilter filter) 或cancelAll(final Object tag) 取消多個(gè)請求。
我們來看一下cancelAll(RequestFilter filter) 方法
/**
* Cancels all requests in this queue for which the given filter applies.
* @param filter The filtering function to use
*/
public void cancelAll(RequestFilter filter) {
synchronized (mCurrentRequests) {
for (Request request : mCurrentRequests) {
if (filter.apply(request)) {
request.cancel();
}
}
}
}
cancelAll需要一個(gè)RequestFilter，RequestFilter是一個(gè)接口，代碼如下
/**
* A simple predicate or filter interface for Requests, for use by
* {@link RequestQueue#cancelAll(RequestFilter)}.
*/
public interface RequestFilter {
public boolean apply(Request request);
}
我們可以通過實(shí)現(xiàn)自己的RequestFilter來取消特定的請求，比如我們可以在apply中判斷request的url是不是http://api.mogujie.org/gw/mwp.timelinemwp.homeListActionlet/1/?data=xxx，若是則返回true，否則返回false，這樣就可以結(jié)束特定url的請求。
cancelAll(final Object tag)中自己實(shí)現(xiàn)了一個(gè)RequestFilter，根據(jù)tag來結(jié)束特定請求，代碼如下：
/**
* Cancels all requests in this queue with the given tag. Tag must be non-null
* and equality is by identity.
*/
public void cancelAll(final Object tag) {
if (tag == null) {
throw new IllegalArgumentException("Cannot cancelAll with a null tag");
}
cancelAll(new RequestFilter() {
@Override
public boolean apply(Request request) {
return request.getTag() == tag;
}
});
}根據(jù)以上代碼可以看出，最終都是調(diào)用了request的cancel方法，cancel中只是簡單的標(biāo)記了一下該request需要結(jié)束，代碼如下：
/**
* Mark this request as canceled. No callback will be delivered.
*/
public void cancel() {
mCanceled = true;
}Volley會在執(zhí)行網(wǎng)絡(luò)請求前和回調(diào)監(jiān)聽前判斷一下標(biāo)記位是否已取消，若取消就結(jié)束自己，不再執(zhí)行網(wǎng)絡(luò)請求，也不回調(diào)，從而達(dá)到取消請求的效果。代碼如下：
NetworkDispatcher 和 CacheDispatcher
@Override
public void run() {
...
while (true) {
try {
...
final Request request = mCacheQueue.take();
...
if (request.isCanceled()) {
request.finish("cache-discard-canceled");
continue;
}
}
}
}ExecutorDelivery中
public void run() {
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);
}緩存處理
HttpHeaderParser.parseCacheHeaders
處理字符串（分割等）得到響應(yīng)頭，并把響應(yīng)頭，body包裝到Cache.Entry中返回。
當(dāng)NetworkDispatcher請求到數(shù)據(jù)后會判斷requset是否需要緩存，需要的話會調(diào)用DiskBasedCache的put(String key, Entry entry)方法，key是url，put中先調(diào)用了pruneIfNeeded，如果緩存新的數(shù)據(jù)后超過規(guī)定大小就先刪除一部分。
/**
* Prunes the cache to fit the amount of bytes specified.
* @param neededSpace The amount of bytes we are trying to fit into the cache.
*/
private void pruneIfNeeded(int neededSpace) {
if ((mTotalSize + neededSpace) < mMaxCacheSizeInBytes) {
return;
}
long before = mTotalSize;
Iterator> iterator = mEntries.entrySet().iterator();
while (iterator.hasNext()) {
Map.Entry entry = iterator.next();
CacheHeader e = entry.getValue();
boolean deleted = getFileForKey(e.key).delete();
if (deleted) {
mTotalSize -= e.size;
}
iterator.remove();
if ((mTotalSize + neededSpace) < mMaxCacheSizeInBytes * HYSTERESIS_FACTOR) {
break;
}
}
}
put中可以看到數(shù)據(jù)被保存到了文件中。
/**
* Puts the entry with the specified key into the cache.
*/
@Override
public synchronized void put(String key, Entry entry) {
pruneIfNeeded(entry.data.length);
File file = getFileForKey(key);
try {
BufferedOutputStream fos = new BufferedOutputStream(new FileOutputStream(file));
CacheHeader e = new CacheHeader(key, entry);
boolean success = e.writeHeader(fos);
if (!success) {
fos.close();
VolleyLog.d("Failed to write header for %s", file.getAbsolutePath());
throw new IOException();
}
fos.write(entry.data);
fos.close();
putEntry(key, e);
return;
} catch (IOException e) {
}
boolean deleted = file.delete();
if (!deleted) {
VolleyLog.d("Could not clean up file %s", file.getAbsolutePath());
}
}Request請求失敗重試機(jī)制
Volley的請求重試機(jī)制是在Request中設(shè)置的，這樣的好處是每一個(gè)Request都可以有自己的重試機(jī)制，代碼如下
/**
* Creates a new request with the given method (one of the values from {@link Method}),
* URL, and error listener. Note that the normal response listener is not provided here as
* delivery of responses is provided by subclasses, who have a better idea of how to deliver
* an already-parsed response.
*/
public Request(int method, String url, Response.ErrorListener listener) {
mMethod = method;
mUrl = url;
mErrorListener = listener;
setRetryPolicy(new DefaultRetryPolicy());
mDefaultTrafficStatsTag = findDefaultTrafficStatsTag(url);
}Request#setRetryPolicy中只是記錄了一下RetryPolicy
/**
* Sets the retry policy for this request.
*
* @return This Request object to allow for chaining.
*/
public Request setRetryPolicy(RetryPolicy retryPolicy) {
mRetryPolicy = retryPolicy;
return this;
}DefaultRetryPolicy實(shí)現(xiàn)了RetryPolicy接口，根據(jù)接口我們可以看到DefaultRetryPolicy可以提供當(dāng)前超時(shí)時(shí)間，當(dāng)前重試次數(shù)等
/**
* Retry policy for a request.
*/
public interface RetryPolicy {
/**
* Returns the current timeout (used for logging).
*/
public int getCurrentTimeout();
/**
* Returns the current retry count (used for logging).
*/
public int getCurrentRetryCount();
/**
* Prepares for the next retry by applying a backoff to the timeout.
* @param error The error code of the last attempt.
* @throws VolleyError In the event that the retry could not be performed (for example if we
* ran out of attempts), the passed in error is thrown.
*/
public void retry(VolleyError error) throws VolleyError;
}BasicNetwork中performRequest中請求失?。⊿ocketTimeoutException，ConnectTimeoutException等）時(shí)會再次請求一次（默認(rèn)重試一次）
若還是失敗就會拋出VolleyError異常
具體代碼如下：
public NetworkResponse performRequest(Request request) throws VolleyError {
...
while (true) {
...
try {
...
httpResponse = mHttpStack.performRequest(request, headers);
...
return new NetworkResponse(statusCode, responseContents, responseHeaders, false,
SystemClock.elapsedRealtime() - requestStart);
} catch (SocketTimeoutException e) {
attemptRetryOnException("socket", request, new TimeoutError());
} catch (ConnectTimeoutException e) {
attemptRetryOnException("connection", request, new TimeoutError());
} catch (MalformedURLException e) {
throw new RuntimeException("Bad URL " + request.getUrl(), e);
} catch (IOException e) {
...
}
}
}
attemptRetryOnException代碼如下：
private static void attemptRetryOnException(String logPrefix, Request request,
VolleyError exception) throws VolleyError {
RetryPolicy retryPolicy = request.getRetryPolicy();
int oldTimeout = request.getTimeoutMs();
try {
retryPolicy.retry(exception);
} catch (VolleyError e) {
request.addMarker(
String.format("%s-timeout-giveup [timeout=%s]", logPrefix, oldTimeout));
throw e;
}
request.addMarker(String.format("%s-retry [timeout=%s]", logPrefix, oldTimeout));
}request.getRetryPolicy()得到的是DefaultRetryPolicy類，DefaultRetryPolicy中retry方法
public void retry(VolleyError error) throws VolleyError {
mCurrentRetryCount++;
mCurrentTimeoutMs += (mCurrentTimeoutMs * mBackoffMultiplier);
if (!hasAttemptRemaining()) {
throw error;
}
}
//Returns true if this policy has attempts remaining, false otherwise.
protected boolean hasAttemptRemaining() {
return mCurrentRetryCount <= mMaxNumRetries;
}request.getRetryPolicy() 得到的是 DefaultRetryPolicy 對象，request重試次數(shù)超過規(guī)定的次數(shù)時(shí)
attemptRetryOnException 就會拋出 VolleyError，從而導(dǎo)致 performRequest() 方法中 while
循環(huán)終止，同時(shí)繼續(xù)向上拋異常。
PoolingByteArrayOutputStream & ByteArrayPool
為了避免讀取服務(wù)端數(shù)據(jù)時(shí)反復(fù)的內(nèi)存申請，Volley提供了PoolingByteArrayOutputStream和ByteArrayPool。
我們先看一下PoolingByteArrayOutputStream的父類ByteArrayOutputStream
/**
* The byte array containing the bytes written.
*/
protected byte[] buf;
/**
* The number of bytes written.
*/
protected int count;ByteArrayOutputStream中提供了兩個(gè)protected 的byte[] buf 和 int count，buf用于write時(shí)保存數(shù)據(jù)，count記錄buf已使用的大小，因?yàn)槎际莗rotected，所有在子類中可以對其進(jìn)行修改。
我們來看一下ByteArrayOutputStream的write方法，可以看到write中調(diào)用了擴(kuò)展buf大小的expand方法，再來看一下expand的具體實(shí)現(xiàn)
private void expand(int i) {
/* Can the buffer handle @i more bytes, if not expand it */
if (count + i <= buf.length) {
return;
}
byte[] newbuf = new byte[(count + i) * 2];
System.arraycopy(buf, 0, newbuf, 0, count);
buf = newbuf;
}
可以看到當(dāng)已使用的空間+要寫入的大小>buf大小時(shí)，直接new 了一個(gè)兩倍大小的空間，并把原來的buf中的數(shù)據(jù)復(fù)制到了新的空間中，最后把新分配的空間賦值給了buf，原來的buf由于沒有被任何對象持有，最終會被回收掉。PoolingByteArrayOutputStream就是在重寫的expand對buf進(jìn)行了處理。
@Override
public synchronized void write(byte[] buffer, int offset, int len) {
Arrays.checkOffsetAndCount(buffer.length, offset, len);
if (len == 0) {
return;
}
expand(len);
System.arraycopy(buffer, offset, buf, this.count, len);
this.count += len;
}
/**
* Writes the specified byte {@code oneByte} to the OutputStream. Only the
* low order byte of {@code oneByte} is written.
*
* @param oneByte
* the byte to be written.
*/
@Override
public synchronized void write(int oneByte) {
if (count == buf.length) {
expand(1);
}
buf[count++] = (byte) oneByte;
}接下來我們看一下PoolingByteArrayOutputStream是怎么復(fù)用內(nèi)存空間的。
在執(zhí)行網(wǎng)絡(luò)請求的BasicNetwork我們看到new 了一個(gè)ByteArrayPool
/**
* @param httpStack HTTP stack to be used
*/
public BasicNetwork(HttpStack httpStack) {
// If a pool isn't passed in, then build a small default pool that will give us a lot of
// benefit and not use too much memory.
this(httpStack, new ByteArrayPool(DEFAULT_POOL_SIZE));
}我們看一下ByteArrayPool的構(gòu)造函數(shù)
/** The buffer pool, arranged both by last use and by buffer size */
private List mBuffersByLastUse = new LinkedList();
private List mBuffersBySize = new ArrayList(64);
/**
* @param sizeLimit the maximum size of the pool, in bytes
*/
public ByteArrayPool(int sizeLimit) {
mSizeLimit = sizeLimit;
}
可以看到ByteArrayPool只是記錄了一下最大的內(nèi)存池空間，默認(rèn)是4096 bytes，并創(chuàng)建了兩個(gè)保存byte[]數(shù)組的List。
為什么要有兩個(gè)List , mBuffersBySize用于二分查找，(int pos = Collections.binarySearch(mBuffersBySize, buf, BUF_COMPARATOR);)。mBuffersByLastUse用于LRU（Least recently used，最近最少使用）置換算法。
我們從BasicNetwork中看到讀取服務(wù)端數(shù)據(jù)時(shí)調(diào)用了entityToBytes方法
/** Reads the contents of HttpEntity into a byte[]. */
private byte[] entityToBytes(HttpEntity entity) throws IOException, ServerError {
PoolingByteArrayOutputStream bytes =
new PoolingByteArrayOutputStream(mPool, (int) entity.getContentLength());
byte[] buffer = null;
try {
InputStream in = entity.getContent();
if (in == null) {
throw new ServerError();
}
buffer = mPool.getBuf(1024);
int count;
while ((count = in.read(buffer)) != -1) {
bytes.write(buffer, 0, count);
}
return bytes.toByteArray();
} finally {
try {
// Close the InputStream and release the resources by "consuming the content".
entity.consumeContent();
} catch (IOException e) {
// This can happen if there was an exception above that left the entity in
// an invalid state.
VolleyLog.v("Error occured when calling consumingContent");
}
mPool.returnBuf(buffer);
bytes.close();
}
}
entityToBytes中又new 了一個(gè)PoolingByteArrayOutputStream，PoolingByteArrayOutputStream是繼承自java.io.ByteArrayOutputStream的。我們看一下PoolingByteArrayOutputStream構(gòu)造函數(shù)
/**
* Constructs a new {@code ByteArrayOutputStream} with a default size of {@code size} bytes. If
* more than {@code size} bytes are written to this instance, the underlying byte array will
* expand.
*
* @param size initial size for the underlying byte array. The value will be pinned to a default
* minimum size.
*/
public PoolingByteArrayOutputStream(ByteArrayPool pool, int size) {
mPool = pool;
buf = mPool.getBuf(Math.max(size, DEFAULT_SIZE));
}PoolingByteArrayOutputStream構(gòu)造函數(shù)中調(diào)用了mPool.getBuf并賦值給了父類的buf，所以以后調(diào)用write時(shí)都是把數(shù)據(jù)寫到了mPool.getBuf得到的byte[]數(shù)組中，也就是byte[]池中。getBuf代碼如下：
/**
* Returns a buffer from the pool if one is available in the requested size, or allocates a new
* one if a pooled one is not available.
*
* @param len the minimum size, in bytes, of the requested buffer. The returned buffer may be
* larger.
* @return a byte[] buffer is always returned.
*/
public synchronized byte[] getBuf(int len) {
for (int i = 0; i < mBuffersBySize.size(); i++) {
byte[] buf = mBuffersBySize.get(i);
if (buf.length >= len) {
mCurrentSize -= buf.length;
mBuffersBySize.remove(i);
mBuffersByLastUse.remove(buf);
return buf;
}
}
return new byte[len];
}由于內(nèi)存池是被多個(gè)NetworkDispatcher公用的，所以getBuf前加了synchronized，getBuf就是從byte[]池中找一個(gè)滿足大小的空間返回，并從List移除掉，若沒有足夠大的則new一個(gè)。再來看一下PoolingByteArrayOutputStream的write方法
@Override
public synchronized void write(byte[] buffer, int offset, int len) {
expand(len);
super.write(buffer, offset, len);
}
@Override
public synchronized void write(int oneByte) {
expand(1);
super.write(oneByte);
}可以看到write中調(diào)用了expand方法，這個(gè)方法不是ByteArrayOutputStream中的，而是PoolingByteArrayOutputStream重寫的，現(xiàn)在看一下expand方法
/**
* Ensures there is enough space in the buffer for the given number of additional bytes.
*/
private void expand(int i) {
/* Can the buffer handle @i more bytes, if not expand it */
if (count + i <= buf.length) {
return;
}
byte[] newbuf = mPool.getBuf((count + i) * 2);
System.arraycopy(buf, 0, newbuf, 0, count);
mPool.returnBuf(buf);
buf = newbuf;
}
expand中沒有調(diào)用父類的expand方法，其與父類expand方法的卻別就是由每次的new byte[]變成了從byte[]池中獲取。
在entityToBytes方法中我們看到用完之后又調(diào)用了mPool.returnBuf(buffer);把byte[]歸還給了byte[]池，代碼如下：
/**
* Returns a buffer to the pool, throwing away old buffers if the pool would exceed its allotted
* size.
*
* @param buf the buffer to return to the pool.
*/
public synchronized void returnBuf(byte[] buf) {
if (buf == null || buf.length > mSizeLimit) {
return;
}
mBuffersByLastUse.add(buf);
int pos = Collections.binarySearch(mBuffersBySize, buf, BUF_COMPARATOR);
if (pos < 0) {
pos = -pos - 1;
}
mBuffersBySize.add(pos, buf);
mCurrentSize += buf.length;
trim();
}
/**
* Removes buffers from the pool until it is under its size limit.
*/
private synchronized void trim() {
while (mCurrentSize > mSizeLimit) {
byte[] buf = mBuffersByLastUse.remove(0);
mBuffersBySize.remove(buf);
mCurrentSize -= buf.length;
}
}Volley加載圖片
Volley除了可以獲取json還可以加載圖片，用法如下：
ImageRequest imageRequest = new ImageRequest(url,
new Response.Listener() {
@Override
public void onResponse(Bitmap response) {
imageView.setImageBitmap(response);
}
}, 0, 0, Config.RGB_565, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
imageView.setImageResource(R.drawable.default_image);
}
}); ImageRequest的構(gòu)造函數(shù)接收6個(gè)參數(shù)，第一個(gè)參數(shù)就是圖片的URL地址。第二個(gè)參數(shù)是圖片請求成功的回調(diào)，這里我們把返回的Bitmap參數(shù)設(shè)置到ImageView中。第三第四個(gè)參數(shù)分別用于指定允許圖片最大的寬度和高度，如果指定的網(wǎng)絡(luò)圖片的寬度或高度大于這里的最大值，則會對圖片進(jìn)行壓縮，指定成0的話就表示不管圖片有多大，都不會進(jìn)行壓縮。第五個(gè)參數(shù)用于指定圖片的顏色屬性，Bitmap.Config下的幾個(gè)常量都可以在這里使用，其中ARGB_8888可以展示最好的顏色屬性，每個(gè)圖片像素占據(jù)4個(gè)字節(jié)的大小，而RGB_565則表示每個(gè)圖片像素占據(jù)2個(gè)字節(jié)大小。第六個(gè)參數(shù)是圖片請求失敗的回調(diào)，這里我們當(dāng)請求失敗時(shí)在ImageView中顯示一張默認(rèn)圖片。
ImageRequest默認(rèn)采用GET方式獲取圖片，采用ScaleType.CENTER_INSIDE方式縮放圖片
public ImageRequest(String url, Response.Listener listener, int maxWidth, int maxHeight,
ScaleType scaleType, Config decodeConfig, Response.ErrorListener errorListener) {
super(Method.GET, url, errorListener);
setRetryPolicy(new DefaultRetryPolicy(DEFAULT_IMAGE_TIMEOUT_MS, DEFAULT_IMAGE_MAX_RETRIES,
DEFAULT_IMAGE_BACKOFF_MULT));
mListener = listener;
mDecodeConfig = decodeConfig;
mMaxWidth = maxWidth;
mMaxHeight = maxHeight;
mScaleType = scaleType;
}
/**
* For API compatibility with the pre-ScaleType variant of the constructor. Equivalent to
* the normal constructor with {@code ScaleType.CENTER_INSIDE}.
*/
@Deprecated
public ImageRequest(String url, Response.Listener listener, int maxWidth, int maxHeight,
Config decodeConfig, Response.ErrorListener errorListener) {
this(url, listener, maxWidth, maxHeight,
ScaleType.CENTER_INSIDE, decodeConfig, errorListener);
} 我們來看一下ImageRequest具體執(zhí)行邏輯
@Override
protected Response parseNetworkResponse(NetworkResponse response) {
// Serialize all decode on a global lock to reduce concurrent heap usage.
synchronized (sDecodeLock) {
try {
return doParse(response);
} catch (OutOfMemoryError e) {
VolleyLog.e("Caught OOM for %d byte image, url=%s", response.data.length, getUrl());
return Response.error(new ParseError(e));
}
}
}
/**
* The real guts of parseNetworkResponse. Broken out for readability.
*/
private Response doParse(NetworkResponse response) {
byte[] data = response.data;
BitmapFactory.Options decodeOptions = new BitmapFactory.Options();
Bitmap bitmap = null;
if (mMaxWidth == 0 && mMaxHeight == 0) {
decodeOptions.inPreferredConfig = mDecodeConfig;
bitmap = BitmapFactory.decodeByteArray(data, 0, data.length, decodeOptions);
} else {
// If we have to resize this image, first get the natural bounds.
decodeOptions.inJustDecodeBounds = true;
BitmapFactory.decodeByteArray(data, 0, data.length, decodeOptions);
int actualWidth = decodeOptions.outWidth;
int actualHeight = decodeOptions.outHeight;
// Then compute the dimensions we would ideally like to decode to.
int desiredWidth = getResizedDimension(mMaxWidth, mMaxHeight,
actualWidth, actualHeight, mScaleType);
int desiredHeight = getResizedDimension(mMaxHeight, mMaxWidth,
actualHeight, actualWidth, mScaleType);
// Decode to the nearest power of two scaling factor.
decodeOptions.inJustDecodeBounds = false;
// TODO(ficus): Do we need this or is it okay since API 8 doesn't support it?
// decodeOptions.inPreferQualityOverSpeed = PREFER_QUALITY_OVER_SPEED;
decodeOptions.inSampleSize =
findBestSampleSize(actualWidth, actualHeight, desiredWidth, desiredHeight);
Bitmap tempBitmap =
BitmapFactory.decodeByteArray(data, 0, data.length, decodeOptions);
// If necessary, scale down to the maximal acceptable size.
if (tempBitmap != null && (tempBitmap.getWidth() > desiredWidth ||
tempBitmap.getHeight() > desiredHeight)) {
bitmap = Bitmap.createScaledBitmap(tempBitmap,
desiredWidth, desiredHeight, true);
tempBitmap.recycle();
} else {
bitmap = tempBitmap;
}
}
if (bitmap == null) {
return Response.error(new ParseError(response));
} else {
return Response.success(bitmap, HttpHeaderParser.parseCacheHeaders(response));
}
}
doParse中對圖片進(jìn)行了縮放處理,可以看到當(dāng)mMaxWidth == 0 && mMaxHeight == 0時(shí)，沒有做過多的處理，這種情況適合于不打的圖片，否則容易導(dǎo)致內(nèi)存溢出。else中對圖片進(jìn)行了縮放處理，首先創(chuàng)建一個(gè)Options 對象，并設(shè)置decodeOptions.inJustDecodeBounds = true，然后使用BitmapFactory.decodeByteArray(data, 0, data.length, decodeOptions);時(shí)就可以只獲取圖片的大小，而不需要把data數(shù)組轉(zhuǎn)換成bitmap，BitmapFactory.decodeByteArray(data, 0, data.length, decodeOptions);可以直接從內(nèi)存中獲取圖片的寬高，之后就可以使用int actualWidth = decodeOptions.outWidth;int actualHeight = decodeOptions.outHeight;
來獲取圖片寬高了。
獲取到圖片寬高后需要通過findBestSampleSize找到一個(gè)合適的縮放比例并賦值給decodeOptions.inSampleSize，縮放比例一定是2的n次冪。即使不是2的冪最終也會按2的n次冪處理
static int findBestSampleSize(
int actualWidth, int actualHeight, int desiredWidth, int desiredHeight) {
double wr = (double) actualWidth / desiredWidth;
double hr = (double) actualHeight / desiredHeight;
double ratio = Math.min(wr, hr);
float n = 1.0f;
while ((n * 2) <= ratio) {
n *= 2;
}
return (int) n;
} /**
* If set to a value > 1, requests the decoder to subsample the original
* image, returning a smaller image to save memory. The sample size is
* the number of pixels in either dimension that correspond to a single
* pixel in the decoded bitmap. For example, inSampleSize == 4 returns
* an image that is 1/4 the width/height of the original, and 1/16 the
* number of pixels. Any value <= 1 is treated the same as 1. Note: the
* decoder uses a final value based on powers of 2, any other value will
* be rounded down to the nearest power of 2.
*/
public int inSampleSize;獲取到縮放比例后就可以通過一下代碼獲取到圖片了
decodeOptions.inJustDecodeBounds = false;
decodeOptions.inSampleSize =
findBestSampleSize(actualWidth, actualHeight, desiredWidth, desiredHeight);
Bitmap tempBitmap =BitmapFactory.decodeByteArray(data, 0, data.length, decodeOptions);
Handler
Volley進(jìn)行網(wǎng)絡(luò)請求是在非ui線程中進(jìn)行的，回調(diào)是怎么跑到ui線程中執(zhí)行的呢？
Volley在創(chuàng)建RequestQueue時(shí)new 了一個(gè) ExecutorDelivery(new Handler(Looper.getMainLooper()))
public RequestQueue(Cache cache, Network network, int threadPoolSize) {
this(cache, network, threadPoolSize,
new ExecutorDelivery(new Handler(Looper.getMainLooper())));
}
以前使用handler時(shí)我們都是直接new Handler(),沒有跟任何參數(shù)，但不跟參數(shù)的Handler默認(rèn)使用的是該線程獨(dú)有的Looper，默認(rèn)情況下ui線程是有Looper的而其他線程是沒有Looper的，在非UI線程中直接new Handler（）會出錯(cuò)，我們可以通過Looper.getMainLooper()得到ui線程的Looper，這樣任何線程都可以使用ui線程的Looper了，而且可以在任何線程中創(chuàng)建Handler，并且使用handler發(fā)送消息時(shí)就會跑到ui線程執(zhí)行了。
也就是說如果我們想在任何線程中都可以創(chuàng)建Hadler，并且handler發(fā)送的消息要在ui線程執(zhí)行的話，就可以采用這種方式創(chuàng)建Handler
new Handler(Looper.getMainLooper());volley gson改造
在實(shí)際開發(fā)中我們會遇到對文字表情的混排處理，一種做法是服務(wù)端直接返回轉(zhuǎn)意后的字符串（比如 ? 用 \:wx 代替），然后客戶端每次都要在ui線程中解析字符串轉(zhuǎn)換成Spanned，若是在ListView中，滾動(dòng)就會非?？D。
我們可以自定義一個(gè)XJsonRequestResponse中把圖文混拍json轉(zhuǎn)換成Spanned即可，由于Response是在非ui線程中執(zhí)行的，所已不會導(dǎo)致ANR。
demo如下：
先看效果圖：
代碼如下：
String json = "{\"nickname\":\"xiaoming\",\"age\":10,\"emoj\":\"[:f001}[:f002}[:f003}hello[:f004}[:f005}\"}";
jsonTv.setText(json);
Gson gson = new GsonBuilder().registerTypeAdapter(Spanned.class, new String2Spanned()).create();
Person person = gson.fromJson(json, Person.class);
editText.append(person.getNickname());
editText.append(" ");
editText.append(person.getAge() + " ");
editText.append(person.getEmoj());
tv.append(Spanned2String.parse(editText.getText())); public class Person {
private Spanned emoj;
private String nickname;
private int age;
}
/**
* 字符串轉(zhuǎn)表情Spanned 表情格式 [:f000}
*
* @author wanjian
*
*/
public class String2Spanned extends TypeAdapter {
static Pattern pattern;
static Map map = new HashMap();
static ImageGetter imageGetter = new ImageGetter() {
@Override
public Drawable getDrawable(String source) {
int id = Integer.parseInt(source);
Drawable d = MyApplication.application.getResources().getDrawable(id);
d.setBounds(0, 0, d.getIntrinsicWidth(), d.getIntrinsicHeight());
return d;
}
};
static {
pattern = Pattern.compile("\\[:f\\d{3}\\}");
//省略部分代碼
map.put("[:f000}", R.drawable.f000);
map.put("[:f001}", R.drawable.f001);
map.put("[:f002}", R.drawable.f002);
map.put("[:f003}", R.drawable.f003);
map.put("[:f004}", R.drawable.f004);
map.put("[:f005}", R.drawable.f005);
}
@Override
public Spanned read(JsonReader in) throws IOException {
if (in.peek() == JsonToken.NULL) {
in.nextNull();
return null;
}
String origStr = in.nextString();
Matcher matcher = pattern.matcher(origStr);
StringBuilder stringBuilder = new StringBuilder();
int last = 0;
while (matcher.find()) {
int s = matcher.start();
int e = matcher.end();
stringBuilder.append(origStr.substring(last, s));
String group = matcher.group();
Integer emojId = map.get(group);
if (emojId == null) {
stringBuilder.append(group);
} else {
stringBuilder.append("");
}
last = e;
}
stringBuilder.append(origStr.substring(last, origStr.length()));
// String ss = "";
return Html.fromHtml(stringBuilder.toString(), imageGetter, null);
}
@Override
public void write(JsonWriter arg0, Spanned arg1) throws IOException {
}
}
import org.apache.commons.lang.StringEscapeUtils;
/**
* 表情轉(zhuǎn) 字符串
* @author wanjian
*
*/
public class Spanned2String {
//
// hello
static Pattern pattern;
static Mapmap=new HashMap<>();
static{
pattern=Pattern.compile("");
//省略部分代碼
map.put(String.valueOf(R.drawable.f000) , "[:f000}");
map.put(String.valueOf(R.drawable.f001) , "[:f001}");
map.put(String.valueOf(R.drawable.f002) , "[:f002}");
map.put(String.valueOf(R.drawable.f003) , "[:f003}");
map.put(String.valueOf(R.drawable.f004) , "[:f004}");
}
public static String decode(String str) {
String[] tmp = str.split(";&#|&#|;");
StringBuilder sb = new StringBuilder("");
for (int i = 0; i < tmp.length; i++) {
if (tmp[i].matches("\\d{5}")) {
sb.append((char) Integer.parseInt(tmp[i]));
} else {
sb.append(tmp[i]);
}
}
return sb.toString();
}
public static String parse(Spanned spanned ) {
try {
String origHtml= Html.toHtml(spanned);
//某些機(jī)型Html.toHtml得到的字符串略有區(qū)別，需要處理下
//模擬器： 慢慢
//小米2A 慢慢
String origStr=origHtml.substring(origHtml.indexOf(">")+1, origHtml.length()-5);
origStr=StringEscapeUtils.unescapeHtml(origStr);//html 漢字實(shí)體編碼轉(zhuǎn)換
Matcher matcher=pattern.matcher(origStr);
// hello
StringBuilder stringBuilder=new StringBuilder();
int last=0;
while (matcher.find()) {
int s= matcher.start();
int e=matcher.end();
stringBuilder.append(origStr.substring( last,s));
String group=matcher.group();
String id=group.substring(10, group.length()-2);
String emojStr=map.get(id);
if (emojStr==null) {
stringBuilder.append(group);
}else{
stringBuilder.append(emojStr);
}
last=e;
}
stringBuilder.append(origStr.substring(last, origStr.length()));
return stringBuilder.toString().replace("
", "\n");
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
return "";
}
}
} volley okhttp改造
public class OkHttpStack implements HttpStack {
private final OkHttpClient mClient;
public OkHttpStack(OkHttpClient client) {
this.mClient = client;
}
@Override
public HttpResponse performRequest(com.android.volley.Request request, Map additionalHeaders)
throws IOException, AuthFailureError {
OkHttpClient client = mClient.clone();
int timeoutMs = request.getTimeoutMs();
client.setConnectTimeout(timeoutMs, TimeUnit.MILLISECONDS);
client.setReadTimeout(timeoutMs, TimeUnit.MILLISECONDS);
client.setWriteTimeout(timeoutMs, TimeUnit.MILLISECONDS);
com.squareup.okhttp.Request.Builder okHttpRequestBuilder = new com.squareup.okhttp.Request.Builder();
okHttpRequestBuilder.url(request.getUrl());
Map headers = request.getHeaders();
for (final String name : headers.keySet()) {
if (name!=null&& headers.get(name)!=null) {
okHttpRequestBuilder.addHeader(name, headers.get(name));
}
}
for (final String name : additionalHeaders.keySet()) {
if (name!=null&& headers.get(name)!=null)
okHttpRequestBuilder.addHeader(name, additionalHeaders.get(name));
}
setConnectionParametersForRequest(okHttpRequestBuilder, request);
com.squareup.okhttp.Request okHttpRequest = okHttpRequestBuilder.build();
Response okHttpResponse = client.newCall(okHttpRequest).execute();
StatusLine responseStatus = new BasicStatusLine(parseProtocol(okHttpResponse.protocol()), okHttpResponse.code(),
okHttpResponse.message());
BasicHttpResponse response = new BasicHttpResponse(responseStatus);
response.setEntity(entityFromOkHttpResponse(okHttpResponse));
Headers responseHeaders = okHttpResponse.headers();
for (int i = 0, len = responseHeaders.size(); i < len; i++) {
final String name = responseHeaders.name(i), value = responseHeaders.value(i);
if (name != null) {
response.addHeader(new BasicHeader(name, value));
}
}
return response;
}
private static HttpEntity entityFromOkHttpResponse(Response r) throws IOException {
BasicHttpEntity entity = new BasicHttpEntity();
ResponseBody body = r.body();
entity.setContent(body.byteStream());
entity.setContentLength(body.contentLength());
entity.setContentEncoding(r.header("Content-Encoding"));
if (body.contentType() != null) {
entity.setContentType(body.contentType().type());
}
return entity;
}
private static void setConnectionParametersForRequest(com.squareup.okhttp.Request.Builder builder,
com.android.volley.Request request) throws IOException, AuthFailureError {
switch (request.getMethod()) {
case com.android.volley.Request.Method.DEPRECATED_GET_OR_POST:
// Ensure backwards compatibility.
// Volley assumes a request with a null body is a GET.
byte[] postBody = request.getPostBody();
if (postBody != null) {
builder.post(RequestBody.create(MediaType.parse(request.getPostBodyContentType()), postBody));
}
break;
case com.android.volley.Request.Method.GET:
builder.get();
break;
case com.android.volley.Request.Method.DELETE:
builder.delete();
break;
case com.android.volley.Request.Method.POST:
builder.post(createRequestBody(request));
break;
case com.android.volley.Request.Method.PUT:
builder.put(createRequestBody(request));
break;
// case com.android.volley.Request.Method.HEAD:
// builder.head();
// break;
//
// case com.android.volley.Request.Method.OPTIONS:
// builder.method("OPTIONS", null);
// break;
//
// case com.android.volley.Request.Method.TRACE:
// builder.method("TRACE", null);
// break;
//
// case com.android.volley.Request.Method.PATCH:
// builder.patch(createRequestBody(request));
// break;
default:
throw new IllegalStateException("Unknown method type.");
}
}
private static ProtocolVersion parseProtocol(final Protocol p) {
switch (p) {
case HTTP_1_0:
return new ProtocolVersion("HTTP", 1, 0);
case HTTP_1_1:
return new ProtocolVersion("HTTP", 1, 1);
case SPDY_3:
return new ProtocolVersion("SPDY", 3, 1);
case HTTP_2:
return new ProtocolVersion("HTTP", 2, 0);
}
throw new IllegalAccessError("Unkwown protocol");
}
private static RequestBody createRequestBody(com.android.volley.Request r) throws AuthFailureError {
final byte[] body = r.getBody();
if (body == null)
return null;
return RequestBody.create(MediaType.parse(r.getBodyContentType()), body);
}
}